Received: (at 65491) by debbugs.gnu.org; 17 Sep 2023 15:22:23 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sun Sep 17 11:22:23 2023 Received: from localhost ([127.0.0.1]:51175 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhtbK-0000f9-SS for submit <at> debbugs.gnu.org; Sun, 17 Sep 2023 11:22:23 -0400 Received: from mail.cs.ucla.edu ([131.179.128.66]:49096) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eggert@HIDDEN>) id 1qhtbD-0000eL-OG for 65491 <at> debbugs.gnu.org; Sun, 17 Sep 2023 11:22:17 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.cs.ucla.edu (Postfix) with ESMTP id 022DE3C00D189; Sun, 17 Sep 2023 08:22:02 -0700 (PDT) Received: from mail.cs.ucla.edu ([127.0.0.1]) by localhost (mail.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id G5kLHPnBVKSn; Sun, 17 Sep 2023 08:22:01 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by mail.cs.ucla.edu (Postfix) with ESMTP id A32583C00D18A; Sun, 17 Sep 2023 08:22:01 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.cs.ucla.edu A32583C00D18A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cs.ucla.edu; s=9D0B346E-2AEB-11ED-9476-E14B719DCE6C; t=1694964121; bh=xN/mZDc41F7KyjDrb2Y2hQchxAYjHir7cIh9E//mz2Q=; h=Message-ID:Date:MIME-Version:To:From; b=MQ1AHq0bO4m/Yut3/wBe/0Ez83P8gpsWS+mfMUVdK4iYtMylUqeoUy2Gx/ure+Fy0 O4BaI1fHU4DH/mRNxUD6Dx0pCQZQWauGXLQzTRHK/kmcv2jMJ4t88mf/XeR76McFtz rgE9gEN39mINOSyRLg3bkdihtX5F2mZZy96nufzAvzUHFTcvHPYMxtTOfmhQ8fgfHY j+uAthbLVzfCrMwYchsCrXYWozCTC5hAW836NJm2ypb8+psKKFzIInRjzq9eWCGYSE pDOeuOJWjHjqCXT4UUaLEDiRntbbC68BLtd3/9O+zwkkMt/b7oBSNL9J+1Iea5xx+A 6GroFnvwOJWlw== X-Virus-Scanned: amavisd-new at mail.cs.ucla.edu Received: from mail.cs.ucla.edu ([127.0.0.1]) by localhost (mail.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id FsLvt-811IIE; Sun, 17 Sep 2023 08:22:01 -0700 (PDT) Received: from [192.168.1.9] (cpe-172-91-119-151.socal.res.rr.com [172.91.119.151]) by mail.cs.ucla.edu (Postfix) with ESMTPSA id 7ADFD3C00D189; Sun, 17 Sep 2023 08:22:01 -0700 (PDT) Message-ID: <a5dd6c16-ebc4-7970-3d94-365766beae72@HIDDEN> Date: Sun, 17 Sep 2023 08:22:01 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 To: Eli Zaretskii <eliz@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> <8af6fa1c-4873-bd6e-e896-ab5bb8d012a2@HIDDEN> <83led5gyxa.fsf@HIDDEN> Content-Language: en-US From: Paul Eggert <eggert@HIDDEN> Organization: UCLA Computer Science Department Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors In-Reply-To: <83led5gyxa.fsf@HIDDEN> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.5 (-) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, mattias.engdegard@HIDDEN, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -2.5 (--) On 2023-09-16 22:18, Eli Zaretskii wrote: > It seems to me that in a 32-bit build with wide > ints just > > #define XUNTAG(a, type, ctype) ((ctype *) XLP (a)) > > should be enough, since XLP yields a 'void *', no? That would complicate the code unnecessarily. Let's not go there. Patch P works as-is, and it's simpler. Let's do that instead. > what I > meant was to have a separate definition of XUNTAG for 32-bit builds > with wide ints (which could still remove the undefined behavior), Yes, that's exactly what I suggest not to do. Why complicate the source code unnecessarily? And if we complicate it here, why not complicate it in similar ways in dozens of other places? I went through a lot of this when adding support for --with-wide-int in the first place, years ago. When doing so, I strove to avoid having multiple copies of the code whenever I could. And I pretty much succeeded: there are only two WITH_WIDE_INT conditionals in lisp.h (and only three in other source files, all introduced relatively recently by others to work around compiler bugs, and all which should be rewritten without the #if). It's an obvious win to have just one copy of the code instead of two, when one copy works and is just as efficient. As much as possible, --with-wide-int should not be a special case. We should not have "#ifdef WITH_WIDE_INT" scattered all over the place. Keep it simple.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 17 Sep 2023 05:19:04 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sun Sep 17 01:19:04 2023 Received: from localhost ([127.0.0.1]:48866 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhkBT-000470-Qt for submit <at> debbugs.gnu.org; Sun, 17 Sep 2023 01:19:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45284) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhkBP-00046V-OU for 65491 <at> debbugs.gnu.org; Sun, 17 Sep 2023 01:19:02 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhkBB-0007c4-Rj; Sun, 17 Sep 2023 01:18:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=sb/x9mAO21Q1ThZAEyJwerAp4dBQ0A/zA8pioBj08Q8=; b=PQpUNl3vxp8p YA2XnckD2a3PC0fH6/v0lYtSh//xURN90PqOziwIYeKxL/thDt/9/HUTnx5QyYS6DStYw8lOvsTIe wBVF2giPm5nt0T5vCNXPdHsaqqdDqNp4ReLUmr4RufiAlSD1FL1KrShxJj+97PP+jv2XwGACBvhcS OZ7a71ncO4YiwKlWzV9MC8LzfwRIRf4xMg/2xmK0M84dPT8AhspBBE6IyxaTEhSJhpHnO0bKmrVc/ 92lBNwKI4PtllSeC0/00gJxNSVT9KEHv8UvWkWivOVxn2DFgao3yanE00r+QLa8bcg+KGsGCPobmR Kep8RrMzL7Zqk4iQFXeHEA==; Date: Sun, 17 Sep 2023 08:18:41 +0300 Message-Id: <83led5gyxa.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Paul Eggert <eggert@HIDDEN> In-Reply-To: <8af6fa1c-4873-bd6e-e896-ab5bb8d012a2@HIDDEN> (message from Paul Eggert on Sat, 16 Sep 2023 12:46:34 -0700) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> <8af6fa1c-4873-bd6e-e896-ab5bb8d012a2@HIDDEN> X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, mattias.engdegard@HIDDEN, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > Date: Sat, 16 Sep 2023 12:46:34 -0700 > Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN > From: Paul Eggert <eggert@HIDDEN> > > On 2023-09-16 10:09, Eli Zaretskii wrote: > > > I also added Paul to the discussion, since he wrote most of the > > involved macros. > > Mattias and I had a private email discussion about XUNTAG last month, > and he's correct that Emacs's current code, which #defines XUNTAG(a, > type, ctype) to ((ctype *) ((char *) XLP (a) - LISP_WORD_TAG (type))), > violates the C standard due to calculating a pointer outside its > containing object's bounds, whereas the patch P that you just reverted, > which defines the same macro to ((ctype *) ((uintptr_t) XLP (a) - > (uintptr_t) LISP_WORD_TAG (type))), does not have that particular > undefined behavior. First, may I ask that in the future such discussions be held on the list, or at least their summary be posted? You can see right here and now how this practice of discussing purely technical issues in private causes unnecessary friction and aggravation, let alone breakage. Next, even if this was discussed, due to our experience with changes in this area, it would have been prudent to post the proposed patch before installing it, so that it could be tested in all the supported configuration before risking such a fundamental breakage of the master branch. You personally do that all the time, and for good reasons, but Mattias has yet to learn that, it seems. More to the point: can you explain how this part ((uintptr_t) XLP (a) - (uintptr_t) LISP_WORD_TAG (type)) works in a 32-bit build --with-wide-int? AFAIU, XLP(a) yields a 32-bit value, and LISP_WORD_TAG has all of its low 32 bits zero, so why do we need the subtraction at all? Aren't we subtracting a zero from what XLP yields? It seems to me that in a 32-bit build with wide ints just #define XUNTAG(a, type, ctype) ((ctype *) XLP (a)) should be enough, since XLP yields a 'void *', no? > I would not favor a two-pronged approach, in which patch P is present > but is used optionally. This would likely cause more trouble than it'd > cure, due to lack of testing of the extra combinations. Let's use just > one approach and keep it simple and more testable. Not sure what you are alluding to here, but if by "two-pronged approach" you mean my suggestion to use cpp conditionals, then what I meant was to have a separate definition of XUNTAG for 32-bit builds with wide ints (which could still remove the undefined behavior), just without all the juggling of integer-to-pointer-and-back conversions, which completely obscure what should be a simple operation of extracting a pointer from an integer by masking some of its bits. Why do I need to fight with these macros each time I read this code, when the job it does is so simple? Thanks.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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Mattias Engdeg=C3=A5rd <mattias.engdegard@HIDDEN> writes:
> 16 sep. 2023 kl. 18.54 skrev Eli Zaretskii <eliz@HIDDEN>:
>
>> It does, but LISP_WORD_TAG(type) is a 64=3Dbit type with the only bits
>> set above 32 bit, so how casting it to uintptr_t is TRT?
>
> Because XUNTAG is used to get the pointer part; we don't want the tag bit=
s.=20
>
>> Why did you need to change the original cast in the first place?
>
> The commit message tried to explain that, but in essence, the old code
> untagged a Lisp_Object value by casting it to char *, then do pointer
> arithmetic on that, and then cast the result to whatever pointer we
> want.
>
> The C standard severely restricts pointer arithmetic: in particular,
> for P+X where X is an integer and P is a pointer, P cannot be null
> (nor will P+X, since both P and P+X must be pointers to objects in the
> same array).
>
> This means that XUNTAG could never reliably untag a null pointer and
> this did cause mayhem in some places. We have just been lucky not to
> trigger it so far but I noticed when attempting to make some
> innocent-looking changes.
Within Standard C, the result of converting a pointer value to an
integer and vice versa is also implementation defined behavior. GCC
regards converting an integer derived from a pointer value back to a
pointer as undefined behavior, should the resulting pointer point to an
object outside that which the pointer value that gave rise to the
original integer references. From `(gcc)Arrays and Pointers':
When casting from pointer to integer and back again, the resulting
pointer must reference the same object as the original pointer,
otherwise the behavior is undefined. That is, one may not use
integer arithmetic to avoid the undefined behavior of pointer
arithmetic as proscribed in C99 and C11 6.5.6/8.
So whether pointer or integer arithmetic is employed in XUNTAG makes no
real difference to us, where undefined behavior is concerned, inasmuch
as other compilers only afford us even more latitude. For example,
Sun's C compiler documentation actively encourages using pointer
arithmetic in lieu of integer arithmetic, and speaks nothing of pointer
arithmetic between different objects being forbidden. And all other
things being equal, I would rather see existing, time-tested, almost
primordial code preserved intact.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 19:46:56 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 15:46:55 2023 Received: from localhost ([127.0.0.1]:48565 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhbFn-00009k-H3 for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 15:46:55 -0400 Received: from mail.cs.ucla.edu ([131.179.128.66]:43394) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eggert@HIDDEN>) id 1qhbFi-00009R-KL for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 15:46:53 -0400 Received: from localhost (localhost [127.0.0.1]) by mail.cs.ucla.edu (Postfix) with ESMTP id C83253C00D189; Sat, 16 Sep 2023 12:46:37 -0700 (PDT) Received: from mail.cs.ucla.edu ([127.0.0.1]) by localhost (mail.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id XqXnop6puLhO; Sat, 16 Sep 2023 12:46:36 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by mail.cs.ucla.edu (Postfix) with ESMTP id F298C3C00D195; Sat, 16 Sep 2023 12:46:35 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.10.3 mail.cs.ucla.edu F298C3C00D195 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cs.ucla.edu; s=9D0B346E-2AEB-11ED-9476-E14B719DCE6C; t=1694893596; bh=G4vG/kLPa2HCW9fSKGe21CxIoiI6W/rjh4rfs4wKPfM=; h=Message-ID:Date:MIME-Version:To:From; b=Loih5slQ80djcVNpL1sW82XHe08arLLEt8WFNkey+c4430hvNtJJ5QLN7T+IHXOG4 +mfDy2budhlLdTS2E2GTH7Z+EKZUCvK1e7wGxgTD3tzjB9ILknyU+QCmDLu2MvHaXN Uh9yFZXLeseoQSR9txwxSCfgsL92uBtW4MufTlp69KKnq56VKKsQMC1BADq2GzWH6T sx8+z89SSfkOSYgEYRE9O0bRR4Vx3Axm1cto46AhvLCs3ObJQWxLjleYZvpmIGG0vZ S0hz1S26gVS6/E/FxPhCAKXa5kbt8nmsmmD4MxsUyl6WBkVcSZpuu4nDnU3czWW00U 5tHbKL+i58NZg== X-Virus-Scanned: amavisd-new at mail.cs.ucla.edu Received: from mail.cs.ucla.edu ([127.0.0.1]) by localhost (mail.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id fVBPbOIWSL53; Sat, 16 Sep 2023 12:46:35 -0700 (PDT) Received: from [192.168.1.9] (cpe-172-91-119-151.socal.res.rr.com [172.91.119.151]) by mail.cs.ucla.edu (Postfix) with ESMTPSA id C5ABC3C00D194; Sat, 16 Sep 2023 12:46:35 -0700 (PDT) Message-ID: <8af6fa1c-4873-bd6e-e896-ab5bb8d012a2@HIDDEN> Date: Sat, 16 Sep 2023 12:46:34 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Content-Language: en-US To: Eli Zaretskii <eliz@HIDDEN>, =?UTF-8?Q?Mattias_Engdeg=c3=a5rd?= <mattias.engdegard@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> From: Paul Eggert <eggert@HIDDEN> Organization: UCLA Computer Science Department Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors In-Reply-To: <83r0mygi4y.fsf@HIDDEN> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.5 (-) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -2.5 (--) On 2023-09-16 10:09, Eli Zaretskii wrote: > I also added Paul to the discussion, since he wrote most of the > involved macros. Mattias and I had a private email discussion about XUNTAG last month, and he's correct that Emacs's current code, which #defines XUNTAG(a, type, ctype) to ((ctype *) ((char *) XLP (a) - LISP_WORD_TAG (type))), violates the C standard due to calculating a pointer outside its containing object's bounds, whereas the patch P that you just reverted, which defines the same macro to ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t) LISP_WORD_TAG (type))), does not have that particular undefined behavior. My own impression is that patch P is a net win, as it should make Emacs more reliable after likely future changes, for two reasons. First, the unpatched version's undefined behavior caused Emacs to crash when Mattias tried out what appeared to be an obvious change to the GC's vector handling. Had patch P been present, Emacs would not have crashed. Second, I vaguely suspect any attempt by Emacs to exploit recent memory safety improvements in Arm, Intel, etc. on GNU/Linux are more likely to work with patch P than without it. I suspect this because most other apps that tag pointers do it in the integer world (as patch P does), not in the pointer world (as Emacs currently does). The developments I have in mind are Arm MTE[1], Intel LAM[2], and (more speculatively) CHERI-RISC-V[3]. Although this is just a suspicion, I suspect I've thought about the issue more than anyone else has. I would not favor a two-pronged approach, in which patch P is present but is used optionally. This would likely cause more trouble than it'd cure, due to lack of testing of the extra combinations. Let's use just one approach and keep it simple and more testable. [1]: https://lwn.net/Articles/834289/ [2]: https://lwn.net/Articles/902094/ [3]: https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/cheri-risc-v.html
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id q2-20020ac24a62000000b00501c673e780sm1118457lfp.84.2023.09.16.12.04.28 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Sep 2023 12:04:29 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <83o7i2gevi.fsf@HIDDEN> Date: Sat, 16 Sep 2023 21:04:28 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <3E9D73A8-BF51-4DBE-87D2-AECEFEA32A0E@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> <8758CDE8-40F1-48DB-9B94-38F771DC8C6C@HIDDEN> <83o7i2gevi.fsf@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, eggert@HIDDEN, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) 16 sep. 2023 kl. 20.19 skrev Eli Zaretskii <eliz@HIDDEN>: > I get it that you are confident, but I want to be confident as well, > and I'm not there yet. That's fine, I'm in no rush. I'll be happy to answer any questions you = may have. It's natural that our perspectives are different. =46rom my point of = view I have a well-researched and carefully tested change with = everything indicating that it's safe and an improvement. But when the = first thing you see is a flood of warnings, it's quite understandable = that it is taken as a sign that something is wrong. > Those special configurations have telltale traits that can be used in > cpp conditionals. IOW, we could have different definitions of XUNTAG > for different configurations. It isn't unheard off, and other macros, > including some that are involved in XUNTAG, do indeed have separate > definitions for several configurations. Certainly, but we didn't need multiple definitions for XUNTAG before and = nothing has changed in that respect. However, if you think that it would make the code easier to understand = we could separate the code into two or more #if clauses, although most = of the time a single definition is easier to maintain. In any case, that would be a separate change.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 18:19:54 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 14:19:54 2023 Received: from localhost ([127.0.0.1]:48508 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhZtZ-0006Ih-Nc for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 14:19:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40570) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhZtU-0006IN-MQ for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 14:19:51 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhZtG-0005Qa-LM; Sat, 16 Sep 2023 14:19:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=ahpGsW+Eb0HHxgbjYzd1V17g7eo8gpdTcbqJJap/nPc=; b=NSv9LFmsTXMsBhIIsnoE Yxiqhi9VS4lAxoWBbG+fFTatrh4/QMrEXG0X+gekb9aj38VX9q70UU5VyUMZUuMrp8PdpxFs+MgXA EIdK7jPypszd5v9S1HmxNdQd4GgmhVzNdZnRETf1NWkz8HijL0cFoOTqG4gNmJQklGUMIJGIphAzM JrGU6Y76hYMS0vaHEi6b6xoPF1bHU168lPUFC+JXBmvxVrQOYtsY4HJAnlfa2drSEQTBxqBJXWAaa 3xsePPGmocDDGc5HDWqohUAKwU3v2kYbyS5p+1WIdrh3qJh7RqD4JI9wgqHZwwGWfqKjZdndz7dgC Am9lemWWxv12tQ==; Date: Sat, 16 Sep 2023 21:19:29 +0300 Message-Id: <83o7i2gevi.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <8758CDE8-40F1-48DB-9B94-38F771DC8C6C@HIDDEN> (message from Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 16 Sep 2023 19:22:54 +0200) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> <8758CDE8-40F1-48DB-9B94-38F771DC8C6C@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, eggert@HIDDEN, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Mattias Engdegård <mattias.engdegard@HIDDEN> > Date: Sat, 16 Sep 2023 19:22:54 +0200 > Cc: Paul Eggert <eggert@HIDDEN>, > 65491 <at> debbugs.gnu.org, > monnier@HIDDEN > > 16 sep. 2023 kl. 19.09 skrev Eli Zaretskii <eliz@HIDDEN>: > > > Sorry, I cannot accept this kind of "discussions" when such tricky > > issues come up. What's the rush of installing changes when you still > > didn't answer my questions, and we still are not sure these changes > > are correct? > > I'm confident that they are correct. Moreover, I'm also confident that the old code was incorrect, which is why the change was carried out. Both the C standard and modern C compilers agree. > > There's nothing strange or unusual that the 32-bit --with-wide-int configuration sees unexpected warnings when code is changed. You must have seen that many times before. It doesn't mean that there is anything wrong with the change; in this case it was just a somewhat pedantic GCC warning, quickly silenced. I get it that you are confident, but I want to be confident as well, and I'm not there yet. A discussion is not over until all of its parties say it is. By rushing to install changes while the discussion is still not over you create an unhealthy atmosphere where some people might conclude their opinions, questions, and doubts are ignored, and that doesn't contribute to the sense of cooperation towards common goals. > >>> It does, but LISP_WORD_TAG(type) is a 64=bit type with the only bits > >>> set above 32 bit, so how casting it to uintptr_t is TRT? > >> > >> Because XUNTAG is used to get the pointer part; we don't want the tag bits. > > > > Then just casting should do, no? Why the subtraction? > > Because when Lisp_Object is pointer-sized we need to remove the tag bits from the word. Only in the special configuration with a Lisp_Object that is larger than pointers can we simply cast away the tag bits. Those special configurations have telltale traits that can be used in cpp conditionals. IOW, we could have different definitions of XUNTAG for different configurations. It isn't unheard off, and other macros, including some that are involved in XUNTAG, do indeed have separate definitions for several configurations.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id q17-20020ac25151000000b004fe3c53bb69sm1100909lfd.307.2023.09.16.10.22.55 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Sep 2023 10:22:55 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <83r0mygi4y.fsf@HIDDEN> Date: Sat, 16 Sep 2023 19:22:54 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <8758CDE8-40F1-48DB-9B94-38F771DC8C6C@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> <83r0mygi4y.fsf@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, Paul Eggert <eggert@HIDDEN>, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) 16 sep. 2023 kl. 19.09 skrev Eli Zaretskii <eliz@HIDDEN>: > Sorry, I cannot accept this kind of "discussions" when such tricky > issues come up. What's the rush of installing changes when you still > didn't answer my questions, and we still are not sure these changes > are correct? I'm confident that they are correct. Moreover, I'm also confident that = the old code was incorrect, which is why the change was carried out. = Both the C standard and modern C compilers agree. There's nothing strange or unusual that the 32-bit --with-wide-int = configuration sees unexpected warnings when code is changed. You must = have seen that many times before. It doesn't mean that there is anything = wrong with the change; in this case it was just a somewhat pedantic GCC = warning, quickly silenced. >>> It does, but LISP_WORD_TAG(type) is a 64=3Dbit type with the only = bits >>> set above 32 bit, so how casting it to uintptr_t is TRT? >>=20 >> Because XUNTAG is used to get the pointer part; we don't want the tag = bits.=20 >=20 > Then just casting should do, no? Why the subtraction? Because when Lisp_Object is pointer-sized we need to remove the tag bits = from the word. Only in the special configuration with a Lisp_Object that = is larger than pointers can we simply cast away the tag bits.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 17:12:16 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 13:12:16 2023 Received: from localhost ([127.0.0.1]:48484 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhYq7-0004Qc-Pn for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 13:12:16 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:37812) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhYq5-0004QP-BL for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 13:12:15 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhYps-0000Be-PZ; Sat, 16 Sep 2023 13:12:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=bX9lTN+Nl0dd8hItPeUHcRcl6IuTdQGbfdDVZsBkY4E=; b=B8Ot3u+ON4IAdUHzQCb2 qhEWP2DOku3UjfN+cB35hsMEhQ2sx8vap+OLwI8dh6GSx4cuoF3EX1fHzBVt/ujW69DH/3dlL+6B3 ww7pIh8yc2+rK2h6VBeci1fGRssa3vcd6CCcm2OTCoK++kQZJpC8B5Fk15T5EySXaz0vx75aeysel QKZ66YJZMI33R5nFKhDdzYHJRabllUVWcB6iu45kiloe1cAzjY0loax1WCyZZVGTGAqE5kf344K31 sGyTADrsGeSSY6uoeOsulJVzb4LML1tTSx7iShTwoEjFQXDOihT+fLr72GzC/Dx2Dt/+OZeYy4P7e nSScBUQPFXoIDQ==; Date: Sat, 16 Sep 2023 20:11:56 +0300 Message-Id: <83pm2igi03.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <DB1F1173-0C57-45A6-AE7E-F5D156F9103C@HIDDEN> (message from Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 16 Sep 2023 19:03:33 +0200) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <83sf7egitx.fsf@HIDDEN> <DB1F1173-0C57-45A6-AE7E-F5D156F9103C@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Mattias Engdegård <mattias.engdegard@HIDDEN> > Date: Sat, 16 Sep 2023 19:03:33 +0200 > Cc: 65491 <at> debbugs.gnu.org, > monnier@HIDDEN > > 16 sep. 2023 kl. 18.54 skrev Eli Zaretskii <eliz@HIDDEN>: > > > It does, but LISP_WORD_TAG(type) is a 64=bit type with the only bits > > set above 32 bit, so how casting it to uintptr_t is TRT? > > Because XUNTAG is used to get the pointer part; we don't want the tag bits. Then just casting should do, no? Why the subtraction? > > Why did you need to change the original cast in the first place? > > The commit message tried to explain that, but in essence, the old code untagged a Lisp_Object value by casting it to char *, then do pointer arithmetic on that, and then cast the result to whatever pointer we want. > > The C standard severely restricts pointer arithmetic: in particular, for P+X where X is an integer and P is a pointer, P cannot be null (nor will P+X, since both P and P+X must be pointers to objects in the same array). > > This means that XUNTAG could never reliably untag a null pointer and this did cause mayhem in some places. We have just been lucky not to trigger it so far but I noticed when attempting to make some innocent-looking changes. Sorry, this is not a reason good enough to make changes in these parts. However "unreliable" the old code worked for many moons, luck or no luck, so if there's no other reason, I prefer to leave it alone. And I'd like to hear from Paul before we make any further changes in that area, please.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 17:09:24 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 13:09:24 2023 Received: from localhost ([127.0.0.1]:48479 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhYnM-0004Lp-7r for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 13:09:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:56714) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhYnI-0004LW-B5 for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 13:09:23 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhYn5-0007Ut-6S; Sat, 16 Sep 2023 13:09:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=vgIjwl749QWDJH8iZMAqUsUHbQFzbDFAZ9d1tpMIJd4=; b=K20u8oxyKA+ufXT5oJZl DhLNxb4gEnekp4s7PvmGRWGF1tkWyZwcDhF+iUVCq0Bg5wQAoeWl7DGk168i30KpZNWNsf9ygqGQg j64Cei9kefaARmaKnRJyIy7lwDbFMcDpZ+qI7RTQmIh6qIk1WbVfM00YAngvTb2UQyBOpODotPg4Y pkddvfvgQP3bJW8vWYYHnXtaDG94zd6yHU/XPQE6ujeQjQjI51n8ChovYB0S2/k4rMMPNGppidtgu 5EK624C/CX9qBqNyZZN4euO0lI8P7YDLsZdignuaa53QL0gb6s9yCMxtQ+SE8QYRKvqRCsMbJ58SZ TaaBoA4awSjMfA==; Date: Sat, 16 Sep 2023 20:09:01 +0300 Message-Id: <83r0mygi4y.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN>, Paul Eggert <eggert@HIDDEN> In-Reply-To: <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> (message from Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 16 Sep 2023 18:54:27 +0200) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <FA940FDA-6FFB-4E80-B254-9266CD5E673A@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Mattias Engdegård <mattias.engdegard@HIDDEN> > Date: Sat, 16 Sep 2023 18:54:27 +0200 > Cc: 65491 <at> debbugs.gnu.org, > monnier@HIDDEN > > 16 sep. 2023 kl. 18.32 skrev Mattias Engdegård <mattias.engdegard@HIDDEN>: > > > #define XUNTAG(a, type, ctype) \ > > ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t)LISP_WORD_TAG (type))) > > I pushed this to master after some experiments. Sorry, I cannot accept this kind of "discussions" when such tricky issues come up. What's the rush of installing changes when you still didn't answer my questions, and we still are not sure these changes are correct? We are touching the deepest bowels of the implementation, so some caution, even trepidation, is in order. So I've reverted the last two changes. Let's finish discussing the need for this change and why you think the last variant is TRT, and install then whatever we decide is needed. I also added Paul to the discussion, since he wrote most of the involved macros.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id r7-20020a2eb607000000b002bf7fd1d336sm1243792ljn.14.2023.09.16.10.03.34 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Sep 2023 10:03:34 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <83sf7egitx.fsf@HIDDEN> Date: Sat, 16 Sep 2023 19:03:33 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <DB1F1173-0C57-45A6-AE7E-F5D156F9103C@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> <83sf7egitx.fsf@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) 16 sep. 2023 kl. 18.54 skrev Eli Zaretskii <eliz@HIDDEN>: > It does, but LISP_WORD_TAG(type) is a 64=3Dbit type with the only bits > set above 32 bit, so how casting it to uintptr_t is TRT? Because XUNTAG is used to get the pointer part; we don't want the tag = bits.=20 > Why did you need to change the original cast in the first place? The commit message tried to explain that, but in essence, the old code = untagged a Lisp_Object value by casting it to char *, then do pointer = arithmetic on that, and then cast the result to whatever pointer we = want. The C standard severely restricts pointer arithmetic: in particular, for = P+X where X is an integer and P is a pointer, P cannot be null (nor will = P+X, since both P and P+X must be pointers to objects in the same = array). This means that XUNTAG could never reliably untag a null pointer and = this did cause mayhem in some places. We have just been lucky not to = trigger it so far but I noticed when attempting to make some = innocent-looking changes.
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Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN>
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16 sep. 2023 kl. 18.32 skrev Mattias Engdeg=C3=A5rd =
<mattias.engdegard@HIDDEN>:
> #define XUNTAG(a, type, ctype) \
> ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t)LISP_WORD_TAG (type)))
I pushed this to master after some experiments.
Interestingly, Clang didn't warn about the new code at all. On the other =
hand, it did probably warn about the old code (with your configuration), =
because
char *g(char *p) {return p+(1ULL<<62);}
results in
<source>:8:26: warning: the pointer incremented by 4611686018427387904 =
refers past the last possible element for an array in 32-bit address =
space containing 8-bit (1-byte) elements (max possible 4294967296 =
elements) [-Warray-bounds]
char *g(char *p) {return p+(1ULL<<62);}
^ ~~~~~~~~
<source>:8:9: note: array 'p' declared here
char *g(char *p) {return p+(1ULL<<62);}
^
but GCC thinks it's fine.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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From: Eli Zaretskii <eliz@HIDDEN>
To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN>
In-Reply-To: <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> (message from
Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 16 Sep 2023 18:32:31 +0200)
Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
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> From: Mattias Engdegård <mattias.engdegard@HIDDEN>
> Date: Sat, 16 Sep 2023 18:32:31 +0200
> Cc: 65491 <at> debbugs.gnu.org,
> monnier@HIDDEN
>
> The new XUNTAG is:
>
> #define XUNTAG(a, type, ctype) ((ctype *) \
> ((uintptr_t) XLP (a) - LISP_WORD_TAG (type)))
>
> so you get a warning from what, conversion of a 64-bit number to (ctype *)?
Yes, I think so:
In file included from dispnew.c:27:
lisp.h: In function 'PSEUDOVECTORP':
lisp.h:813:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
813 | #define XUNTAG(a, type, ctype) ((ctype *) \
| ^
lisp.h:374:6: note: in expansion of macro 'XUNTAG'
374 | ((XUNTAG ((a), Lisp_Vectorlike, union vectorlike_header)->size \
| ^~~~~~
lisp.h:1127:10: note: in expansion of macro 'lisp_h_PSEUDOVECTORP'
1127 | return lisp_h_PSEUDOVECTORP (a, code);
| ^~~~~~~~~~~~~~~~~~~~
lisp.h: In function 'XSYMBOL_WITH_POS':
lisp.h:813:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
813 | #define XUNTAG(a, type, ctype) ((ctype *) \
| ^
lisp.h:1152:12: note: in expansion of macro 'XUNTAG'
1152 | return XUNTAG (a, Lisp_Vectorlike, struct Lisp_Symbol_With_Pos);
| ^~~~~~
lisp.h: In function 'XBARE_SYMBOL':
lisp.h:813:33: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
813 | #define XUNTAG(a, type, ctype) ((ctype *) \
| ^
lisp.h:1159:27: note: in expansion of macro 'XUNTAG'
1159 | intptr_t i = (intptr_t) XUNTAG (a, Lisp_Symbol, struct Lisp_Symbol);
| ^~~~~~
> Does changing the definition to
>
> #define XUNTAG(a, type, ctype) \
> ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t)LISP_WORD_TAG (type)))
>
> help? (That is, cast the LISP_WORD_TAG return value to uintptr_t.)
It does, but LISP_WORD_TAG(type) is a 64=bit type with the only bits
set above 32 bit, so how casting it to uintptr_t is TRT?
Why did you need to change the original cast in the first place?
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id n9-20020ac242c9000000b00501c022163dsm1077446lfl.222.2023.09.16.09.32.32 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Sep 2023 09:32:32 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <83ttrugkj2.fsf@HIDDEN> Date: Sat, 16 Sep 2023 18:32:31 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <B8175B38-691A-459A-B454-9AFE2ED7E254@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> <83ttrugkj2.fsf@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) 16 sep. 2023 kl. 18.17 skrev Eli Zaretskii <eliz@HIDDEN>: >> The latter one completely broke the 32-bit build --with-wide-int, = most >> probably because the last argument to XUNTAG is frequently a pointer >> to a 64-bit type, where uintptr_t is only 32-bit wide. >=20 > No, that's not it: the reason is that the _first_ argument is a 64-bit > data type, and then casting XLP(a) to uintptr_t causes the warning, > because uintptr_t is a 32-bit type. Let's see if I understand this correctly, as I can't try that = configuration myself. In your configuration, Lisp_Object is a 64-bit integer (or a struct = containing one). LISP_WORD_TAG(type) is also a 64-bit integer with tag bits at the top = (USE_LSB_TAG=3D0). The old XUNTAG was: #define XUNTAG(a, type, ctype) ((ctype *) \ ((char *) XLP (a) - LISP_WORD_TAG = (type))) so that we get a subtraction of a pointer and a very large 64-bit = number, which results in just the pointer. The new XUNTAG is: #define XUNTAG(a, type, ctype) ((ctype *) \ ((uintptr_t) XLP (a) - LISP_WORD_TAG = (type))) so you get a warning from what, conversion of a 64-bit number to (ctype = *)? Does changing the definition to #define XUNTAG(a, type, ctype) \ ((ctype *) ((uintptr_t) XLP (a) - (uintptr_t)LISP_WORD_TAG (type))) help? (That is, cast the LISP_WORD_TAG return value to uintptr_t.)
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 16:17:41 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 12:17:40 2023 Received: from localhost ([127.0.0.1]:48401 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhXzI-0002qR-M8 for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 12:17:40 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48740) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhXzG-0002qE-Pb for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 12:17:39 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhXz4-0004aq-8P; Sat, 16 Sep 2023 12:17:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=Ey7fiVN7dgfWSBZeR+4SGMTi12Q7YFgmb9kW37QSkqw=; b=kwjJdzN031ia R3Q56COHra6Ee367wZhzDX8TCUuScbqnctcVfbCfL/vR44k7sZXxCoSsuROnhxC1Y16aw/gon+qSa ejYn4gS21eQMH2RFWLGNCmYWGbWAw2mho/2WlHahEFS883SDUKkkMhKDdLlULIAxdMKopvOTt3l9Q BexzUKzeoJDwOuAR+7E+8xfNbTXKODaAoTKQTBbt6T4YeUjhmGK2trJEEzL95IkttsQJWDjylOjNg b3qzo0WITyomi6qo4h58QV2P9lIV1sEAKpSOObILpmTGvAoVnjJy7PuuodHxdZDzqqoFzV6HCVQbN Fm6+4HcKfDrdkuXUWiundw==; Date: Sat, 16 Sep 2023 19:17:21 +0300 Message-Id: <83ttrugkj2.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: mattias.engdegard@HIDDEN In-Reply-To: <83v8cagkqv.fsf@HIDDEN> (message from Eli Zaretskii on Sat, 16 Sep 2023 19:12:40 +0300) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> <83v8cagkqv.fsf@HIDDEN> X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN > Date: Sat, 16 Sep 2023 19:12:40 +0300 > From: Eli Zaretskii <eliz@HIDDEN> > > The latter one completely broke the 32-bit build --with-wide-int, most > probably because the last argument to XUNTAG is frequently a pointer > to a 64-bit type, where uintptr_t is only 32-bit wide. No, that's not it: the reason is that the _first_ argument is a 64-bit data type, and then casting XLP(a) to uintptr_t causes the warning, because uintptr_t is a 32-bit type.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 16 Sep 2023 16:13:02 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Sep 16 12:13:02 2023 Received: from localhost ([127.0.0.1]:48384 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qhXuo-0002i7-CD for submit <at> debbugs.gnu.org; Sat, 16 Sep 2023 12:13:02 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53938) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qhXul-0002hh-32 for 65491 <at> debbugs.gnu.org; Sat, 16 Sep 2023 12:13:00 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qhXuX-0003bq-V6; Sat, 16 Sep 2023 12:12:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=ewGVqglYgN/G1frVeGH0HAvce08VwGzKijs7MKGtXHE=; b=bLzd7UGujP4kdqRPFniJ pO/sEbh/W9upwou3+kMcjuwCf5XqZCvEoW3rBs/k3RPBIRpdFXCql3/FUFc/Zyl0tPTfYy9C7Azed svXlo/H3HQXFtI5ik7H2fBANM1UB4nWKI7fCYQJYHsbTg/6WAEjsssvubT4rBgwtHgCh3FD9idAkD w12MEW66130SwTDNbPYJKEci4MgTBUyXzqwQFs6kJLMMNJ7+jZft0Ml4kVmA+hC7EY5r32BZ/4jry 5XmiOXyApEhTu9XHzjj2csl7eWi81Gnm2DKEq4flV/cAbFnNU6NzXMY4omPElS83Y8ylsexzWAVFW KyLXXIsb/dKGcQ==; Date: Sat, 16 Sep 2023 19:12:40 +0300 Message-Id: <83v8cagkqv.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> (message from Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 16 Sep 2023 16:58:01 +0200) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Mattias Engdegård <mattias.engdegard@HIDDEN> > Date: Sat, 16 Sep 2023 16:58:01 +0200 > Cc: 65491 <at> debbugs.gnu.org, > Eli Zaretskii <eliz@HIDDEN> > > I also pushed two small changes that were essential to working with the code so we might just as well have them in now: b1881d7dab (fix a static assertion) and 056c99a34c (better Lisp_Object untagging). The latter one completely broke the 32-bit build --with-wide-int, most probably because the last argument to XUNTAG is frequently a pointer to a 64-bit type, where uintptr_t is only 32-bit wide. As result, I cannot even compile Emacs: each C file emits the same warnings, which fill up my screen in a matter of milliseconds. Please try to fix this ASAP, as it makes me unable to work on master.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id l10-20020ac24a8a000000b004fdd9d43e05sm1065025lfp.171.2023.09.16.07.58.02 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 16 Sep 2023 07:58:02 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> Date: Sat, 16 Sep 2023 16:58:01 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <6B2EDD07-AAEB-40E8-B369-F634296BD3D9@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> To: Stefan Monnier <monnier@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, Eli Zaretskii <eliz@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) Results of some further experiments: - Reducing the `vector_free_lists` array to its actually used first half = does improve performance a bit, even with subsequent scanning speed-ups. - Enlarging `struct vector_block` from 4 KiB does not necessarily speed = things up but more measurement is needed. - Using a bitmap for faster `vector_free_lists` scanning is definitely = beneficial. - The previously mentioned hack where scanning begins in the most = recently added bucket is surprisingly effective, often even more so than = a bitmap, but I'm wary of it being brittle. Need more measurements. - Our special-casing of the bool-vector representation is annoying. It = would be good if we didn't have to pay the price on 64-bit platforms. I also pushed two small changes that were essential to working with the = code so we might just as well have them in now: b1881d7dab (fix a static = assertion) and 056c99a34c (better Lisp_Object untagging). I'd like to try size-homogeneous blocks as well, but this requires some = GC updates. Just a matter of taking the time, of course.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Stefan Kangas <stefankangas@HIDDEN>
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> The reason might be that vector sizes are distributed non-uniformly and
> some segments of vector_free_lists are filled more than others.
Indeed, I'd expect that at any given time, many buckets of
`vector_free_lists` are empty.
Also, when ELisp code allocates many structs of the same size, the first
few allocations may be satisfied by free elements in the appropriate
bucket, but very quickly that bucket will become empty, so we'll look
for the next non-empty bucket, and the remaining slightly-smaller free
vector will then be put back into a lower bucket but the next allocation
will go through the same loop to find that same "slightly-smaller free
vector", to make it yet a bit smaller, ... until it's all consumed after
which we'll look for the next bigger free vector etc...
So your code makes a lot of sense from that point of view.
Many mallocs approach the problem by creating whole pages dedicated to
a given object size, so when the bucket is empty, N new free vectors of
that exact size are created (in a new vector-block) and put into the
appropriate bucket so the next N allocations of that same size will
quickly find a free vector. Since all those vector-blocks are made of
vectors of the same size, the size info can be shared between them
instead of each one of them carrying its own size.
[ In our case, vectors need to carry their size for other purposes than
memory management, so it's not clear we'd gain much there.
But it could help make `live_small_vector_holding` faster. ]
Stefan
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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>> @@ -3426,6 +3428,7 @@ sweep_vectors (void)
>> gcstat.total_vectors = 0;
>> gcstat.total_vector_slots = gcstat.total_free_vector_slots = 0;
>> memset (vector_free_lists, 0, sizeof (vector_free_lists));
>> + last_known_vector_free_idx = VECTOR_MAX_FREE_LIST_INDEX;
>>
>> /* Looking through vector blocks. */
>
> Hmm... so I was wrong and after GC there are aren't any free vectors?
> I need to go re-read that code, then, because it doesn't match my mental
> model of how it work(s|ed).
Ah, no, I see what's going on: the above code is run at the *beginning*
of `sweep_vectors` before we discover which (free) vectors remain.
Stefan
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From: Ihor Radchenko <yantar92@HIDDEN>
To: Stefan Monnier <monnier@HIDDEN>
Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
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Stefan Monnier <monnier@HIDDEN> writes:
>> +static ptrdiff_t last_known_vector_free_idx = VECTOR_MAX_FREE_LIST_INDEX;
>> /* Singly-linked list of large vectors. */
>>
>> static struct large_vector *large_vectors;
>
> There's clearly some spacing issue with the following comment but more
> importantly the new var would need a good comment explaining what the
> variable should hold and why it's useful, so we know when it's safe and
> desirable to set or use the var.
Sure. I can add a comment. However, from previous answers, we may better
rewrite the vector allocation code more significantly.
>> - for (index = VINDEX (nbytes + VBLOCK_BYTES_MIN);
>> + for (index = max (VINDEX (nbytes + VBLOCK_BYTES_MIN), last_known_vector_free_idx);
>> index < VECTOR_MAX_FREE_LIST_INDEX; index++)
>> if (vector_free_lists[index])
>> {
>
> IIUC that's the core of your patch. Nice.
>> memset (vector_free_lists, 0, sizeof (vector_free_lists));
>> + last_known_vector_free_idx = VECTOR_MAX_FREE_LIST_INDEX;
>>
>> /* Looking through vector blocks. */
>
> Hmm... so I was wrong and after GC there are aren't any free vectors?
> I need to go re-read that code, then, because it doesn't match my mental
> model of how it work(s|ed).
Interestingly, when I just tried to skip searching vector_free_lists
when there are no vectors available there, it yielded to no significant
improvement.
Only that max(VINDEX (...), last_known_vector_free_idx) yielded a good
performance improvement.
The reason might be that vector sizes are distributed non-uniformly and
some segments of vector_free_lists are filled more than others.
It could be a good exercise to look into statistics of how
vector_free_lists is filled. Is there some standard way to print debug
information from the allocation code?
--
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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From: Stefan Monnier <monnier@HIDDEN>
To: Ihor Radchenko <yantar92@HIDDEN>
Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
In-Reply-To: <87y1i0iwvu.fsf@localhost> (Ihor Radchenko's message of "Thu, 24
Aug 2023 09:59:33 +0000")
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> This patch adds a heuristic that reduces the time spent searching
> `vector_free_lists' when trying to allocate a new vector.
The microbenchmarks give surprisingly good performance improvements.
> `vector_free_lists' is a rather long array with few hundreds of
> elements. And it does not make sense to check the whole array in
> `allocate_vector_from_block' if we can get information about free vector
> that was recently made available of if we know for sure that no free
> vectors are available (after GC).
Hmm... after GC we should usually have a non-zero number of free vectors
available (the unused parts of vector blocks which could not be `free`d
because they still contain a live vector), no?
[ See comment below. ]
> The described approach may sometimes miss free vectors in
> `vector_free_lists', especially if the allocation happens from larger
> vector to smaller.
Right, it could lead to an increase in fragmentation, tho it might tend
to allocate temporally related objects together, which might be beneficial.
> - pack-unpack 0.40=B10.00 -> 0.35=B10.01
Interesting. I didn't expect such a large effect there.
> @@ -3145,6 +3145,7 @@ large_vector_vec (struct large_vector *p)
>=20=20
> static struct Lisp_Vector *vector_free_lists[VECTOR_MAX_FREE_LIST_INDEX];
>=20=20
> +static ptrdiff_t last_known_vector_free_idx =3D VECTOR_MAX_FREE_LIST_IND=
EX;
> /* Singly-linked list of large vectors. */
>=20=20
> static struct large_vector *large_vectors;
There's clearly some spacing issue with the following comment but more
importantly the new var would need a good comment explaining what the
variable should hold and why it's useful, so we know when it's safe and
desirable to set or use the var.
> @@ -3180,6 +3181,7 @@ setup_on_free_list (struct Lisp_Vector *v, ptrdiff_=
t nbytes)
> set_next_vector (v, vector_free_lists[vindex]);
> ASAN_POISON_VECTOR_CONTENTS (v, nbytes - header_size);
> vector_free_lists[vindex] =3D v;
> + last_known_vector_free_idx =3D vindex;
> }
>=20=20
> /* Get a new vector block. */
> @@ -3234,7 +3236,7 @@ allocate_vector_from_block (ptrdiff_t nbytes)
> /* Next, check free lists containing larger vectors. Since
> we will split the result, we should have remaining space
> large enough to use for one-slot vector at least. */
> - for (index =3D VINDEX (nbytes + VBLOCK_BYTES_MIN);
> + for (index =3D max (VINDEX (nbytes + VBLOCK_BYTES_MIN), last_known_vec=
tor_free_idx);
> index < VECTOR_MAX_FREE_LIST_INDEX; index++)
> if (vector_free_lists[index])
> {
IIUC that's the core of your patch. Nice.
> @@ -3426,6 +3428,7 @@ sweep_vectors (void)
> gcstat.total_vectors =3D 0;
> gcstat.total_vector_slots =3D gcstat.total_free_vector_slots =3D 0;
> memset (vector_free_lists, 0, sizeof (vector_free_lists));
> + last_known_vector_free_idx =3D VECTOR_MAX_FREE_LIST_INDEX;
>=20=20
> /* Looking through vector blocks. */
Hmm... so I was wrong and after GC there are aren't any free vectors?
I need to go re-read that code, then, because it doesn't match my mental
model of how it work(s|ed).
Stefan
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id y24-20020ac24478000000b0050096712dc0sm1084630lfl.222.2023.08.27.02.54.39 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sun, 27 Aug 2023 02:54:39 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> In-Reply-To: <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> Date: Sun, 27 Aug 2023 11:54:38 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <311389CC-D412-42B0-92BA-CA52972C3E95@HIDDEN> References: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> <jwvcyz9amx4.fsf-monnier+emacs@HIDDEN> To: Stefan Monnier <monnier@HIDDEN> X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, Eli Zaretskii <eliz@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) 26 aug. 2023 kl. 16.55 skrev Stefan Monnier <monnier@HIDDEN>: >> - 4096 bytes for vector blocks seems a tad small >=20 > AFAIK this number was chosen arbitrarily and we never tried to tune = it, > so there's probably room for improvement, indeed. > Note that many vectors will be small (they're really Lisp structs), = tho. That's definitely the case, and the same allocation mechanism is used = for many other fairly small objects. Another observation is that most vectorlike allocations are fixed-size. = This is mostly true even for nominally variable-sized objects (vectors = and records) because as you say, they are often used as (fixed-sized) = structs. We might want to segregate allocations by size entirely and cease = splitting longer vectors. That, with larger and N-bit aligned blocks, = would provide rapid access to common metadata from any object pointer. = This may reduce GC costs; will have to look at that. Naturally, allocation and GC costs must be considered together (and = run-time, in case we change representation which is occasionally = warranted). > It's important to improve efficiency of vector allocation because it > allows us to get rid of specialized allocations we're using for other > Lisp types. E.g. we got rid of the specialized `marker_block`s we = used > to use for markers and overlays (and a handful of more esoteric data > types), and next in line are the `symbol_block`s and = `interval_block`s. Yes, many important object types are fixed-sized vectorlike allocations. = Allocations tend to be spikey in size; that's why vector_free_lists is = so sparse and should probably be reformed.
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From: Stefan Monnier <monnier@HIDDEN>
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Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
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> - isn't vector_free_list twice as big as it needs to be?
> - 4096 bytes for vector blocks seems a tad small
AFAIK this number was chosen arbitrarily and we never tried to tune it,
so there's probably room for improvement, indeed.
Note that many vectors will be small (they're really Lisp structs), tho.
> - to what extent are we duplicating the work done by modern libc allocators
> (very generously including glibc here)?
We are exactly duplicating that code (and poorly so, as is the rule),
but there's a reason for it: we need to allocate those vectors within
specifically marked/known address ranges so that our conservative
stack scanning can distinguish "potential valid pointer to a vector"
from "definitely not a pointer to a vector".
It would be nice if we could more or less literally copy the code of
a good malloc library.
[ The previous vector allocation code was even more costly because every
vector allocation came together with allocation and insertion of a new
node in the red-black tree where we keep track of which ranges of
memory hold which kind of data. ]
It's important to improve efficiency of vector allocation because it
allows us to get rid of specialized allocations we're using for other
Lisp types. E.g. we got rid of the specialized `marker_block`s we used
to use for markers and overlays (and a handful of more esoteric data
types), and next in line are the `symbol_block`s and `interval_block`s.
Stefan
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 14:54:49 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 10:54:49 2023 Received: from localhost ([127.0.0.1]:43294 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZuga-0001FS-KI for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 10:54:48 -0400 Received: from mout02.posteo.de ([185.67.36.66]:38315) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <yantar92@HIDDEN>) id 1qZugW-0001FB-Mc for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 10:54:47 -0400 Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 954C8240104 for <65491 <at> debbugs.gnu.org>; Sat, 26 Aug 2023 16:54:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1693061673; bh=bcERCLW0G9xl9+b84Ba/w7MaXonLew1ubKmRg7Vi1I8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version: Content-Transfer-Encoding:From; b=MZ/fRmpG53OQNvVY1OKl7AWoaVp1j9vL4Fg1hswRTylXOfAZ13RiKozBYEozV898Y nKG/lxHYJQmFPb+Uy0gdTjEAIaxJlj6tmdqnKgYo9ErSzG9YA+DAK3853W31B109SH UDki8vAyUNprl5ZFKF4oYNx3+vyC/48zIZK70Juhx4JEFuc63g/9yi9g8cA17845fy WYOrno+cAr42nMl7vmtubitPcayffICHZ3s1s1MxuNDcDqvgSOmmLY8XQiLZ5EtBPm bZTMa1nzYy4XyximKyiHHwsDMTRRfi96nbiniSCj3UcGaGZJyZIvNgDhhReLNAcz7n a6o4GENuFVIng== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4RY0GC2VY4z6txf; Sat, 26 Aug 2023 16:54:27 +0200 (CEST) From: Ihor Radchenko <yantar92@HIDDEN> To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors In-Reply-To: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> References: <87y1i0iwvu.fsf@localhost> <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> Date: Sat, 26 Aug 2023 14:54:55 +0000 Message-ID: <87y1hxj1kw.fsf@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, Eli Zaretskii <eliz@HIDDEN>, Stefan Monnier <monnier@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) Mattias Engdeg=C3=A5rd <mattias.engdegard@HIDDEN> writes: > First of all, let's leave bignums out of this entirely. They are not rele= vant here. > > Second, please do not motivate any perceived performance problem from > benchmarks found on the internet, especially anything derived from the > Gabriel benchmarks. This includes the benchmarks in ELPA. > That said, vectorlike object allocation in general is definitely > relevant and can certainly be improved but I'm not persuaded by the > proposed patch. Please do not apply it right away. I have no problem with this and I have supplied more relevant benchmarks with Org and with composition (as suggested by Eli). Of course, the problem is not with bignums - it just revealed the inefficiency with array iteration I tried to address. If more can be done with vectorlike allocation, it will be even better. > However, the important part is not the patch but the problem it highlight= s, and here there is evidently plenty to do.=20 > > For example: > > - isn't vector_free_list twice as big as it needs to be? AFAIR, trying to reduce this array size was the first thing I tried. When I touched VECTOR_BLOCK_SIZE, I got segfaults and compilation failures. (Do note that I am missing understanding about the motivation behind this constant). > - to what extent are we duplicating the work done by modern libc allocato= rs (very generously including glibc here)? > - next_vector is a dangerously unstable concoction of C undefined behavio= ur Isn't vector_free_list following the pattern used across alloc.c? For example, Fcons uses a similar idea with holding pre-allocated memory as a chain of pointers. --=20 Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at <https://orgmode.org/>. Support Org development at <https://liberapay.com/org-mode>, or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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[188.150.165.235]) by smtp.gmail.com with ESMTPSA id z8-20020ac24188000000b004ff8e245260sm688761lfh.15.2023.08.26.05.01.48 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 26 Aug 2023 05:01:48 -0700 (PDT) From: =?utf-8?Q?Mattias_Engdeg=C3=A5rd?= <mattias.engdegard@HIDDEN> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.120.0.1.15\)) Subject: bug#65491: [PATCH] Improve performance allocating vectors Message-Id: <CA48AA01-4396-48B6-BA80-1A24EF492ED1@HIDDEN> Date: Sat, 26 Aug 2023 14:01:48 +0200 To: 65491 <at> debbugs.gnu.org X-Mailer: Apple Mail (2.3654.120.0.1.15) X-Spam-Score: 0.0 (/) X-Debbugs-Envelope-To: 65491 Cc: Eli Zaretskii <eliz@HIDDEN>, Stefan Monnier <monnier@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -1.0 (-) First of all, let's leave bignums out of this entirely. They are not = relevant here. Second, please do not motivate any perceived performance problem from = benchmarks found on the internet, especially anything derived from the = Gabriel benchmarks. This includes the benchmarks in ELPA. That said, vectorlike object allocation in general is definitely = relevant and can certainly be improved but I'm not persuaded by the = proposed patch. Please do not apply it right away. However, the important part is not the patch but the problem it = highlights, and here there is evidently plenty to do.=20 For example: - isn't vector_free_list twice as big as it needs to be? - 4096 bytes for vector blocks seems a tad small - to what extent are we duplicating the work done by modern libc = allocators (very generously including glibc here)? - not happy with the way struct vector_block co-allocates metadata with = a big power-of-two data chunk - next_vector is a dangerously unstable concoction of C undefined = behaviour and so on.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 09:01:37 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 05:01:37 2023 Received: from localhost ([127.0.0.1]:41737 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZpAn-0005mf-D0 for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 05:01:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58690) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qZpAk-0005mK-5I for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 05:01:36 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qZpAY-0005iV-TZ; Sat, 26 Aug 2023 05:01:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=JHgVi5lUXbVO2oZ19xl+kxStiU5VqD5xZnMVv+1xkNM=; b=dGmqlgox3MUw RZw7QKQWGdW/AJrbd5cfuTe4aJSY2yNywJ9sOL30Cn56i+yb8EKIvvvEjs01nHk5d3jWtaPrQWTy0 3DPis0YGTgZFFek825Zh+XEOEp6rsYoPUaE6WP2XLWWdJPYmYp+938gtLZb8BYazrmL6pVRuJfWp9 9Y+NLHm+Me3GkbEmJDCEGvFO746X2cL8tnrjDXhSmoVrNURFGKvi9o+kP3KpIpMg8kB8y6AxTdFp9 B6dPcO9ouZVwoX4AC0MRtfsqjZDuQJ8YzSDB6I5EgeUeIaS23j11NNPXVIWbQ4JYe3sS/VVitlvvn 5w6EveZUr7XfKl/F9zHE4w==; Date: Sat, 26 Aug 2023 12:01:50 +0300 Message-Id: <83ttsmkwht.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Ihor Radchenko <yantar92@HIDDEN> In-Reply-To: <87o7iu9r6x.fsf@localhost> (message from Ihor Radchenko on Sat, 26 Aug 2023 07:51:50 +0000) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <87y1i0iwvu.fsf@localhost> <83bkeumg17.fsf@HIDDEN> <87ttsm9sbk.fsf@localhost> <837cpimf87.fsf@HIDDEN> <87o7iu9r6x.fsf@localhost> X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Ihor Radchenko <yantar92@HIDDEN> > Cc: monnier@HIDDEN, 65491 <at> debbugs.gnu.org > Date: Sat, 26 Aug 2023 07:51:50 +0000 > > Eli Zaretskii <eliz@HIDDEN> writes: > > >> If you know any useful code that makes heavy use of vector allocation, I > >> can also benchmark it. > > > > Look in the area of encoding/decoding and automatic compositions -- > > these tend to use vectors quite a lot. For example, rendering text > > that uses a script where most of characters are composed, such as > > Arabic or Hangul (Korean) should allocate vectors. Note that this is > > the case where we call Lisp from C display code. > > Do you mean something like scrolling performance when scrolling a large > Arabic/Korean text file? Yes.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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From: Ihor Radchenko <yantar92@HIDDEN>
To: Eli Zaretskii <eliz@HIDDEN>
Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
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Ihor Radchenko <yantar92@HIDDEN> writes:
> Do you mean something like scrolling performance when scrolling a large
> Arabic/Korean text file?
I downloaded Quran from https://tanzil.net/download/, opened it Emacs
like
$ perf record ./src/emacs -Q ~/Downloads/quran-simple-plain.txt
and scrolled the buffer with PgDown all the way to the bottom.
It does not look like allocation vectors is all that heavy here
(compared to the edge case with fib.el with bignums).
without the patch:
10.14% emacs emacs [.] process_mark_stack
3.79% emacs emacs [.] sub_char_table_ref
3.68% emacs emacs [.] x_draw_glyph_string
2.75% emacs libc.so.6 [.] pthread_mutex_lock
1.75% emacs libc.so.6 [.] 0x0000000000088b0a
-> 1.41% emacs emacs [.] allocate_vectorlike
1.30% emacs emacs [.] sweep_vectors
1.27% emacs emacs [.] char_table_ref
with the patch
9.97% emacs emacs [.] process_mark_stack
4.30% emacs emacs [.] x_draw_glyph_string
3.58% emacs emacs [.] sub_char_table_ref
2.66% emacs libc.so.6 [.] pthread_mutex_lock
1.87% emacs libc.so.6 [.] 0x0000000000088b0a
1.29% emacs emacs [.] sweep_vectors
1.22% emacs emacs [.] face_for_font
1.17% emacs emacs [.] char_table_ref
...
-> 0.26% emacs emacs [.] allocate_vectorlike
1.41% down to 0.26% ~5x speedup.
--
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 07:51:34 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 03:51:34 2023 Received: from localhost ([127.0.0.1]:41664 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZo50-0003kx-5v for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:51:34 -0400 Received: from mout02.posteo.de ([185.67.36.66]:46093) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <yantar92@HIDDEN>) id 1qZo4x-0003kk-Qs for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:51:32 -0400 Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id E8EA9240101 for <65491 <at> debbugs.gnu.org>; Sat, 26 Aug 2023 09:51:20 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1693036280; bh=RI27QKoby/yr/wU2uXsfPf0ywmLeWBrUMEWisRcjZRQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=OD+iGo7jRLcqhGOOKxyLqfmTgFz/CxLaGFOkN8sANNzRGWFWqGyscL8NBPTY1HlYd i0oJvMfpH8N+eRIiJJ3i7SRbCWjq89UqS0bO2rISLo2TZm3qeJQFtcr90Zx+k0gZou cZh/dSXNgo3g/LG7RYzlg2kdkZ1DDr2SO8VGASFEY14f7oELHY/OMMFvBkUeTE1VtP nXFwYf6uuXSCwUIvB/PwQC0FKV6VEaP561eEs+qeU2pA0Wau/d6vG+b9qoMeydkFgU Cn6gUAgB0Ea8OOOA08TsIbbDQOujrVKBhl1UZH95WSF8F0YJZ4bvOB5PGoUl0HnrPH QSleYzn4e+Vkg== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4RXpt01w3bz9s4W; Sat, 26 Aug 2023 09:51:20 +0200 (CEST) From: Ihor Radchenko <yantar92@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors In-Reply-To: <837cpimf87.fsf@HIDDEN> References: <87y1i0iwvu.fsf@localhost> <83bkeumg17.fsf@HIDDEN> <87ttsm9sbk.fsf@localhost> <837cpimf87.fsf@HIDDEN> Date: Sat, 26 Aug 2023 07:51:50 +0000 Message-ID: <87o7iu9r6x.fsf@localhost> MIME-Version: 1.0 Content-Type: text/plain X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) Eli Zaretskii <eliz@HIDDEN> writes: >> If you know any useful code that makes heavy use of vector allocation, I >> can also benchmark it. > > Look in the area of encoding/decoding and automatic compositions -- > these tend to use vectors quite a lot. For example, rendering text > that uses a script where most of characters are composed, such as > Arabic or Hangul (Korean) should allocate vectors. Note that this is > the case where we call Lisp from C display code. Do you mean something like scrolling performance when scrolling a large Arabic/Korean text file? -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at <https://orgmode.org/>. Support Org development at <https://liberapay.com/org-mode>, or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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From: Ihor Radchenko <yantar92@HIDDEN>
To: Eli Zaretskii <eliz@HIDDEN>
Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors
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Cc: 65491 <at> debbugs.gnu.org, Stefan Monnier <monnier@HIDDEN>
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Ihor Radchenko <yantar92@HIDDEN> writes:
> If you know any useful code that makes heavy use of vector allocation, I
> can also benchmark it.
One example is the newer versions of Org parser, where I know for sure
that vector allocation is used. Although the code is mostly doing regexp
search for parsing, so a better real world example would be still useful.
I ran a quick parser run on a large Org file using
(let ((large-file-warning-threshold nil)
(gc-cons-threshold most-positive-fixnum)
(org-inhibit-startup t)
(org-element-cache-persistent nil))
(with-current-buffer (find-file-noselect "~/Org/notes.org")
(message "%s" (benchmark-call (lambda () (org-element-parse-buffer nil nil 'defer))))))
Without the patch:
$ perf record ./src/emacs -Q -batch -L ~/Git/org-mode/lisp -L ~/.emacs.d/eln-cache/30.0.50-17ebec90/ -l org-element -l /tmp/test.el
(15.724130802000001 1 0.429624333)
without the patch:
26.60% emacs emacs [.] exec_byte_code
12.40% emacs emacs [.] re_match_2_internal
8.70% emacs emacs [.] re_search_2
8.19% emacs emacs [.] re_compile_pattern
3.73% emacs emacs [.] re_iswctype
3.60% emacs emacs [.] funcall_subr
3.08% emacs emacs [.] allocate_vectorlike
2.70% emacs emacs [.] plist_get
1.80% emacs emacs [.] buf_charpos_to_bytepos
Vector allocation takes about 3% of the time.
-----------
with the patch, vector allocation contributions drops to 0.42% - 6x
decrease.
-----------
$ perf record ./src/emacs -Q -batch -L ~/Git/org-mode/lisp -L ~/.emacs.d/eln-cache/30.0.50-17ebec90/ -l org-element -l /tmp/test.el
(15.100695088 1 0.43508134400000004)
27.06% emacs emacs [.] exec_byte_code
12.96% emacs emacs [.] re_match_2_internal
8.90% emacs emacs [.] re_search_2
8.55% emacs emacs [.] re_compile_pattern
3.68% emacs emacs [.] re_iswctype
3.57% emacs emacs [.] funcall_subr
2.80% emacs emacs [.] plist_get
...
0.42% emacs emacs [.] allocate_vectorlike
--
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 07:31:35 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 03:31:35 2023 Received: from localhost ([127.0.0.1]:41655 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZnlf-0003De-DZ for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:31:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:41794) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qZnld-0003DR-OZ for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:31:34 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qZnlT-0008Cx-C7; Sat, 26 Aug 2023 03:31:23 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=RxjfNs9jJZ41ehbpL2sxBMxl2LGNXQY+k4aLjwFntWY=; b=ejjYfUWJy0Wy Fyi33nHAT7TyZOnyGOSOAhP0z9qayXIcdxCvvpws+GPOL7GG6iCBFjY7CqDoDBv163AXip73DouJ7 qYbVnzyWdyJBcciOxEye+YJN3jOfBKPketSTzXk+Ho8LPP3boqOiShf5F1MMi0RtIM/oI19r1n1Xc PGqPS1BsLjSQoFIDq/xyYZ4guGX9J3yQhBZ+IBq3pFb+UDDESSNp+QK/yXsglzy5easE9UKBznTz5 6jNFzhbR1pwDF0kbjV/XX3O72k+jtAHioNVgOwO0fYKYh8JJyh25ygomus1gw0sKu25sqwBVdPu46 pU1pQFebAhsDAgrj0sVPOQ==; Date: Sat, 26 Aug 2023 10:31:52 +0300 Message-Id: <837cpimf87.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Ihor Radchenko <yantar92@HIDDEN> In-Reply-To: <87ttsm9sbk.fsf@localhost> (message from Ihor Radchenko on Sat, 26 Aug 2023 07:27:27 +0000) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <87y1i0iwvu.fsf@localhost> <83bkeumg17.fsf@HIDDEN> <87ttsm9sbk.fsf@localhost> X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, monnier@HIDDEN X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Ihor Radchenko <yantar92@HIDDEN> > Cc: Stefan Monnier <monnier@HIDDEN>, 65491 <at> debbugs.gnu.org > Date: Sat, 26 Aug 2023 07:27:27 +0000 > > If you know any useful code that makes heavy use of vector allocation, I > can also benchmark it. Look in the area of encoding/decoding and automatic compositions -- these tend to use vectors quite a lot. For example, rendering text that uses a script where most of characters are composed, such as Arabic or Hangul (Korean) should allocate vectors. Note that this is the case where we call Lisp from C display code.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 07:27:13 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 03:27:13 2023 Received: from localhost ([127.0.0.1]:41637 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZnhQ-00034k-Nf for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:27:13 -0400 Received: from mout02.posteo.de ([185.67.36.66]:35533) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <yantar92@HIDDEN>) id 1qZnhM-000346-Vy for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:27:12 -0400 Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 1F3D3240101 for <65491 <at> debbugs.gnu.org>; Sat, 26 Aug 2023 09:26:57 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1693034818; bh=j+gTQ9dTbV2E72R7hD76QGr/SVtxtSPVNCKL3TU9tTU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=VQVJdI4ZBRIoOPivj4jnmVPzGC1HF5+QXWbT1yK9ax39nwM8xSl712DR6gUfrGqqj Ygtg9/YK/cHRH5gzdZJFMywbtXJ2yvRXPh8wqJaZ4ctutAW1GMwqoTmO/6Qwn/HPtj EgnJWi8JLxYTkm1xCol2bZJxxrTN5vR2k2ZV855fPt5Ggi0r+yER8I2GJOqlA5W03P y1hQJPDRRLvs6JM+6W1FK0dkxGuTsGntn4ieEgRwX3CabvricLqI8bC2Rl7mROoaNv x5QlJTeOjexVf3Y1YAWakVGppeO21J6xcutn8mDj8OTqTlMOCQ0x6gtCyhcqwazrlg LRhqhGGzhJLaw== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4RXpKr6QVxz6twF; Sat, 26 Aug 2023 09:26:56 +0200 (CEST) From: Ihor Radchenko <yantar92@HIDDEN> To: Eli Zaretskii <eliz@HIDDEN> Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors In-Reply-To: <83bkeumg17.fsf@HIDDEN> References: <87y1i0iwvu.fsf@localhost> <83bkeumg17.fsf@HIDDEN> Date: Sat, 26 Aug 2023 07:27:27 +0000 Message-ID: <87ttsm9sbk.fsf@localhost> MIME-Version: 1.0 Content-Type: text/plain X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org, Stefan Monnier <monnier@HIDDEN> X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) Eli Zaretskii <eliz@HIDDEN> writes: > my comment is that the savings are quite small, so it seems, so I'm > not sure we should install this. Overall saving are small because the effect is blurred by the code that does not allocate vectors - my patch has 0 effect on such code. Calculations involving vectors are pidigits that is 30% faster and bignum version of fib.el - over 50% faster. If you know any useful code that makes heavy use of vector allocation, I can also benchmark it. -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at <https://orgmode.org/>. Support Org development at <https://liberapay.com/org-mode>, or support my work at <https://liberapay.com/yantar92>
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
Full text available.Received: (at 65491) by debbugs.gnu.org; 26 Aug 2023 07:14:15 +0000 From debbugs-submit-bounces <at> debbugs.gnu.org Sat Aug 26 03:14:15 2023 Received: from localhost ([127.0.0.1]:41622 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <debbugs-submit-bounces <at> debbugs.gnu.org>) id 1qZnUt-0002kV-4c for submit <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:14:15 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40374) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from <eliz@HIDDEN>) id 1qZnUp-0002kG-Az for 65491 <at> debbugs.gnu.org; Sat, 26 Aug 2023 03:14:13 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from <eliz@HIDDEN>) id 1qZnUe-000564-0y; Sat, 26 Aug 2023 03:14:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=aSPkoQSdPSeLxS2o9w5A3ewQn7Er8B2/f6z/fqtFf9w=; b=U/JfocdYoPtbX+op+T0I r6j1ntueQFV2MGT9cWWKgJmfdQCEPCyrz1L/WNjDPYK5QSWGsyfD9aj63+f4iYUg9UMjhEvbmmR89 wbCF3LdKuXIrXn0qwrbnfp3XabZZdIsqiDDkVGnGFMhsF2wShD6dAjS2cTGW9tHHxlpm3iOz8FOBg 2H1Wt78KdLTSX7KJ+QAHHzZs4DO82UJy4jeU+wlPQv6BUCeumfzRm+8ATmLjecbpT+R5xMKsdD+C9 486zWYxH0posXjZazO8hbMH3mENCnX0szj8thzoyHEb6bHq/5A7Hy/7lLDTQQX3vQWHSwXcWdXQFR QNw90HP1jKA4vw==; Date: Sat, 26 Aug 2023 10:14:28 +0300 Message-Id: <83bkeumg17.fsf@HIDDEN> From: Eli Zaretskii <eliz@HIDDEN> To: Ihor Radchenko <yantar92@HIDDEN>, Stefan Monnier <monnier@HIDDEN> In-Reply-To: <87y1i0iwvu.fsf@localhost> (message from Ihor Radchenko on Thu, 24 Aug 2023 09:59:33 +0000) Subject: Re: bug#65491: [PATCH] Improve performance allocating vectors References: <87y1i0iwvu.fsf@localhost> MIME-version: 1.0 Content-type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 65491 Cc: 65491 <at> debbugs.gnu.org X-BeenThere: debbugs-submit <at> debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: <debbugs-submit.debbugs.gnu.org> List-Unsubscribe: <https://debbugs.gnu.org/cgi-bin/mailman/options/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=unsubscribe> List-Archive: <https://debbugs.gnu.org/cgi-bin/mailman/private/debbugs-submit/> List-Post: <mailto:debbugs-submit <at> debbugs.gnu.org> List-Help: <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=help> List-Subscribe: <https://debbugs.gnu.org/cgi-bin/mailman/listinfo/debbugs-submit>, <mailto:debbugs-submit-request <at> debbugs.gnu.org?subject=subscribe> Errors-To: debbugs-submit-bounces <at> debbugs.gnu.org Sender: "Debbugs-submit" <debbugs-submit-bounces <at> debbugs.gnu.org> X-Spam-Score: -3.3 (---) > From: Ihor Radchenko <yantar92@HIDDEN> > Date: Thu, 24 Aug 2023 09:59:33 +0000 > > Following up the bignum performance discussion in > https://yhetil.org/emacs-devel/87bkfdsmde.fsf@localhost > > This patch adds a heuristic that reduces the time spent searching > `vector_free_lists' when trying to allocate a new vector. > > `vector_free_lists' is a rather long array with few hundreds of > elements. And it does not make sense to check the whole array in > `allocate_vector_from_block' if we can get information about free vector > that was recently made available of if we know for sure that no free > vectors are available (after GC). > > In the patch, we start searching `vector_free_lists' no earlier than the > last known index of the available free vector, or skip the search > entirely when there is known index (after sweep). > > The described approach may sometimes miss free vectors in > `vector_free_lists', especially if the allocation happens from larger > vector to smaller. The cost will be slightly higher memory consumption - > no larger than VECTOR_MAX_FREE_LIST_INDEX extra free vectors. > > With the patch, CPU time spent allocating new vectors in the fib.eln > test from https://yhetil.org/emacs-devel/87bkfdsmde.fsf@localhost drops 10x. > > Also, the patch gives a noticeable improvement when running > elisp-benchmarks (ELPA package). The overall speedup is around 10% > (including unaffected tests). > > No single test gets worse within error margins and the following tests > get a significant speedup: > > - eieio 1.32±0.04 -> 1.04±0.03 > - pack-unpack 0.40±0.00 -> 0.35±0.01 > - pidigits 6.00±0.06 -> 4.08±0.12 > > pidigits is no surprise as it likely uses bignums. > > * Results without the patch > > | test | non-gc avg (s) | gc avg (s) | gcs avg | tot avg (s) | tot avg err (s) | > |--------------------+----------------+------------+---------+-------------+-----------------| > | bubble | 0.68 | 0.06 | 1 | 0.73 | 0.05 | > | bubble-no-cons | 1.17 | 0.00 | 0 | 1.17 | 0.07 | > | bytecomp | 1.64 | 0.32 | 13 | 1.95 | 0.03 | > | dhrystone | 2.13 | 0.00 | 0 | 2.13 | 0.02 | > | eieio | 1.19 | 0.13 | 7 | 1.32 | 0.04 | > | fibn | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | fibn-named-let | 1.47 | 0.00 | 0 | 1.47 | 0.04 | > | fibn-rec | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | fibn-tc | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | flet | 1.41 | 0.00 | 0 | 1.41 | 0.03 | > | inclist | 0.84 | 0.00 | 0 | 0.84 | 0.03 | > | inclist-type-hints | 0.76 | 0.00 | 0 | 0.76 | 0.00 | > | listlen-tc | 0.12 | 0.00 | 0 | 0.12 | 0.01 | > | map-closure | 5.25 | 0.00 | 0 | 5.25 | 0.02 | > | nbody | 1.47 | 0.15 | 1 | 1.62 | 0.07 | > | pack-unpack | 0.38 | 0.02 | 1 | 0.40 | 0.00 | > | pack-unpack-old | 1.13 | 0.05 | 3 | 1.19 | 0.03 | > | pcase | 1.77 | 0.00 | 0 | 1.77 | 0.01 | > | pidigits | 5.04 | 0.97 | 17 | 6.00 | 0.06 | > | scroll | 0.58 | 0.00 | 0 | 0.58 | 0.02 | > | smie | 1.47 | 0.05 | 2 | 1.52 | 0.02 | > |--------------------+----------------+------------+---------+-------------+-----------------| > | total | 28.49 | 1.74 | 45 | 30.23 | 0.16 | > > * Results with the patch > > | test | non-gc avg (s) | gc avg (s) | gcs avg | tot avg (s) | tot avg err (s) | > |--------------------+----------------+------------+---------+-------------+-----------------| > | bubble | 0.69 | 0.05 | 1 | 0.74 | 0.07 | > | bubble-no-cons | 1.03 | 0.00 | 0 | 1.03 | 0.02 | > | bytecomp | 1.45 | 0.25 | 13 | 1.70 | 0.10 | > | dhrystone | 1.98 | 0.00 | 0 | 1.98 | 0.05 | > | eieio | 0.92 | 0.12 | 7 | 1.04 | 0.03 | > | fibn | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | fibn-named-let | 1.45 | 0.00 | 0 | 1.45 | 0.12 | > | fibn-rec | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | fibn-tc | 0.00 | 0.00 | 0 | 0.00 | 0.00 | > | flet | 1.39 | 0.00 | 0 | 1.39 | 0.07 | > | inclist | 0.83 | 0.00 | 0 | 0.83 | 0.03 | > | inclist-type-hints | 0.77 | 0.00 | 0 | 0.77 | 0.03 | > | listlen-tc | 0.10 | 0.00 | 0 | 0.10 | 0.00 | > | map-closure | 5.25 | 0.00 | 0 | 5.25 | 0.37 | > | nbody | 1.45 | 0.16 | 1 | 1.60 | 0.05 | > | pack-unpack | 0.33 | 0.02 | 1 | 0.35 | 0.01 | > | pack-unpack-old | 1.07 | 0.06 | 3 | 1.13 | 0.08 | > | pcase | 1.78 | 0.00 | 0 | 1.78 | 0.05 | > | pidigits | 3.15 | 0.92 | 17 | 4.08 | 0.12 | > | scroll | 0.55 | 0.00 | 0 | 0.55 | 0.01 | > | smie | 1.45 | 0.04 | 2 | 1.49 | 0.06 | > |--------------------+----------------+------------+---------+-------------+-----------------| > | total | 25.63 | 1.62 | 45 | 27.25 | 0.45 | > Stefan, any comments? my comment is that the savings are quite small, so it seems, so I'm not sure we should install this.
bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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From: Ihor Radchenko <yantar92@HIDDEN>
To: bug-gnu-emacs@HIDDEN
Subject: [PATCH] Improve performance allocating vectors
Date: Thu, 24 Aug 2023 09:59:33 +0000
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Tags: patch
Hi,
Following up the bignum performance discussion in
https://yhetil.org/emacs-devel/87bkfdsmde.fsf@localhost
This patch adds a heuristic that reduces the time spent searching
`vector_free_lists' when trying to allocate a new vector.
`vector_free_lists' is a rather long array with few hundreds of
elements. And it does not make sense to check the whole array in
`allocate_vector_from_block' if we can get information about free vector
that was recently made available of if we know for sure that no free
vectors are available (after GC).
In the patch, we start searching `vector_free_lists' no earlier than the
last known index of the available free vector, or skip the search
entirely when there is known index (after sweep).
The described approach may sometimes miss free vectors in
`vector_free_lists', especially if the allocation happens from larger
vector to smaller. The cost will be slightly higher memory consumption -
no larger than VECTOR_MAX_FREE_LIST_INDEX extra free vectors.
With the patch, CPU time spent allocating new vectors in the fib.eln
test from https://yhetil.org/emacs-devel/87bkfdsmde.fsf@localhost drops 10x.
Also, the patch gives a noticeable improvement when running
elisp-benchmarks (ELPA package). The overall speedup is around 10%
(including unaffected tests).
No single test gets worse within error margins and the following tests
get a significant speedup:
- eieio 1.32=C2=B10.04 -> 1.04=C2=B10.03
- pack-unpack 0.40=C2=B10.00 -> 0.35=C2=B10.01
- pidigits 6.00=C2=B10.06 -> 4.08=C2=B10.12
pidigits is no surprise as it likely uses bignums.
* Results without the patch
| test | non-gc avg (s) | gc avg (s) | gcs avg | tot avg (s=
) | tot avg err (s) |
|--------------------+----------------+------------+---------+-----------=
--+-----------------|
| bubble | 0.68 | 0.06 | 1 | 0.7=
3 | 0.05 |
| bubble-no-cons | 1.17 | 0.00 | 0 | 1.1=
7 | 0.07 |
| bytecomp | 1.64 | 0.32 | 13 | 1.9=
5 | 0.03 |
| dhrystone | 2.13 | 0.00 | 0 | 2.1=
3 | 0.02 |
| eieio | 1.19 | 0.13 | 7 | 1.3=
2 | 0.04 |
| fibn | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| fibn-named-let | 1.47 | 0.00 | 0 | 1.4=
7 | 0.04 |
| fibn-rec | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| fibn-tc | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| flet | 1.41 | 0.00 | 0 | 1.4=
1 | 0.03 |
| inclist | 0.84 | 0.00 | 0 | 0.8=
4 | 0.03 |
| inclist-type-hints | 0.76 | 0.00 | 0 | 0.7=
6 | 0.00 |
| listlen-tc | 0.12 | 0.00 | 0 | 0.1=
2 | 0.01 |
| map-closure | 5.25 | 0.00 | 0 | 5.2=
5 | 0.02 |
| nbody | 1.47 | 0.15 | 1 | 1.6=
2 | 0.07 |
| pack-unpack | 0.38 | 0.02 | 1 | 0.4=
0 | 0.00 |
| pack-unpack-old | 1.13 | 0.05 | 3 | 1.1=
9 | 0.03 |
| pcase | 1.77 | 0.00 | 0 | 1.7=
7 | 0.01 |
| pidigits | 5.04 | 0.97 | 17 | 6.0=
0 | 0.06 |
| scroll | 0.58 | 0.00 | 0 | 0.5=
8 | 0.02 |
| smie | 1.47 | 0.05 | 2 | 1.5=
2 | 0.02 |
|--------------------+----------------+------------+---------+-----------=
--+-----------------|
| total | 28.49 | 1.74 | 45 | 30.2=
3 | 0.16 |
* Results with the patch
| test | non-gc avg (s) | gc avg (s) | gcs avg | tot avg (s=
) | tot avg err (s) |
|--------------------+----------------+------------+---------+-----------=
--+-----------------|
| bubble | 0.69 | 0.05 | 1 | 0.7=
4 | 0.07 |
| bubble-no-cons | 1.03 | 0.00 | 0 | 1.0=
3 | 0.02 |
| bytecomp | 1.45 | 0.25 | 13 | 1.7=
0 | 0.10 |
| dhrystone | 1.98 | 0.00 | 0 | 1.9=
8 | 0.05 |
| eieio | 0.92 | 0.12 | 7 | 1.0=
4 | 0.03 |
| fibn | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| fibn-named-let | 1.45 | 0.00 | 0 | 1.4=
5 | 0.12 |
| fibn-rec | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| fibn-tc | 0.00 | 0.00 | 0 | 0.0=
0 | 0.00 |
| flet | 1.39 | 0.00 | 0 | 1.3=
9 | 0.07 |
| inclist | 0.83 | 0.00 | 0 | 0.8=
3 | 0.03 |
| inclist-type-hints | 0.77 | 0.00 | 0 | 0.7=
7 | 0.03 |
| listlen-tc | 0.10 | 0.00 | 0 | 0.1=
0 | 0.00 |
| map-closure | 5.25 | 0.00 | 0 | 5.2=
5 | 0.37 |
| nbody | 1.45 | 0.16 | 1 | 1.6=
0 | 0.05 |
| pack-unpack | 0.33 | 0.02 | 1 | 0.3=
5 | 0.01 |
| pack-unpack-old | 1.07 | 0.06 | 3 | 1.1=
3 | 0.08 |
| pcase | 1.78 | 0.00 | 0 | 1.7=
8 | 0.05 |
| pidigits | 3.15 | 0.92 | 17 | 4.0=
8 | 0.12 |
| scroll | 0.55 | 0.00 | 0 | 0.5=
5 | 0.01 |
| smie | 1.45 | 0.04 | 2 | 1.4=
9 | 0.06 |
|--------------------+----------------+------------+---------+-----------=
--+-----------------|
| total | 25.63 | 1.62 | 45 | 27.2=
5 | 0.45 |
In GNU Emacs 30.0.50 (build 54, x86_64-pc-linux-gnu, GTK+ Version
3.24.38, cairo version 1.17.8) of 2023-08-22 built on localhost
Repository revision: c09d78f3c0818d7391760e84f94a442e8beb22dd
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Gentoo Linux
Configured using:
'configure --with-native-compilation
JAVAC=3D/etc/java-config-2/current-system-vm/bin/javac'
--=-=-=
Content-Type: text/patch
Content-Disposition: attachment;
filename=0001-Improve-performance-allocating-vectors.patch
From 476db65dc780d8c501d73dfaaf92c53eb9c73b2f Mon Sep 17 00:00:00 2001
Message-ID: <476db65dc780d8c501d73dfaaf92c53eb9c73b2f.1692869114.git.yantar92@HIDDEN>
From: Ihor Radchenko <yantar92@HIDDEN>
Date: Thu, 24 Aug 2023 11:05:18 +0300
Subject: [PATCH] Improve performance allocating vectors
* src/alloc.c (last_known_vector_free_idx): New global variable
holding the last known free allocated vector index in
`vector_free_lists'.
(setup_on_free_list): Record the vector index when adding a new
allocated vector to `vector_free_lists'.
(allocate_vector_from_block): Add heuristics searching for an existing
allocated vector no earlier than `last_known_vector_free_idx'. This
heuristics may sometimes skip available allocated vectors, but reduces
the number of the `for' loop iterations significantly.
(sweep_vectors): Set `last_known_vector_free_idx' to large value - no
free allocated vectors remain available after sweep operation.
Link: https://yhetil.org/emacs-devel/87bkfdsmde.fsf@localhost
---
src/alloc.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/alloc.c b/src/alloc.c
index c77bdc6372d..4293de2bdf3 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3145,6 +3145,7 @@ large_vector_vec (struct large_vector *p)
static struct Lisp_Vector *vector_free_lists[VECTOR_MAX_FREE_LIST_INDEX];
+static ptrdiff_t last_known_vector_free_idx = VECTOR_MAX_FREE_LIST_INDEX;
/* Singly-linked list of large vectors. */
static struct large_vector *large_vectors;
@@ -3180,6 +3181,7 @@ setup_on_free_list (struct Lisp_Vector *v, ptrdiff_t nbytes)
set_next_vector (v, vector_free_lists[vindex]);
ASAN_POISON_VECTOR_CONTENTS (v, nbytes - header_size);
vector_free_lists[vindex] = v;
+ last_known_vector_free_idx = vindex;
}
/* Get a new vector block. */
@@ -3234,7 +3236,7 @@ allocate_vector_from_block (ptrdiff_t nbytes)
/* Next, check free lists containing larger vectors. Since
we will split the result, we should have remaining space
large enough to use for one-slot vector at least. */
- for (index = VINDEX (nbytes + VBLOCK_BYTES_MIN);
+ for (index = max (VINDEX (nbytes + VBLOCK_BYTES_MIN), last_known_vector_free_idx);
index < VECTOR_MAX_FREE_LIST_INDEX; index++)
if (vector_free_lists[index])
{
@@ -3426,6 +3428,7 @@ sweep_vectors (void)
gcstat.total_vectors = 0;
gcstat.total_vector_slots = gcstat.total_free_vector_slots = 0;
memset (vector_free_lists, 0, sizeof (vector_free_lists));
+ last_known_vector_free_idx = VECTOR_MAX_FREE_LIST_INDEX;
/* Looking through vector blocks. */
--
2.41.0
--=-=-=
Content-Type: text/plain
--
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>
--=-=-=--
Ihor Radchenko <yantar92@HIDDEN>:bug-gnu-emacs@HIDDEN.
Full text available.bug-gnu-emacs@HIDDEN:bug#65491; Package emacs.
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