GNU bug report logs - #47225
QEMU warning about performance

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Leo Famulari <leo <at> famulari.name>
To: bug-guix <at> gnu.org
Subject: QEMU warning about performance
Date: Thu, 18 Mar 2021 02:25:26 -0400

While using `guix system vm`, I noticed this warning. I think it's new,
maybe from the 5.2.0 update?

------
qemu-system-x86_64: warning: 9p: degraded performance: a reasonable high msize should be chosen on client/guest side (chosen msize is <= 8192). See https://wiki.qemu.org/Documentation/9psetup#msize for details.
------

That web page suggests that we increase the virtio packet size when
declaring the 9p file-systems, I think in %linux-vm-file-systems of (gnu
system vm).

Message #10 received at 47225 <at> debbugs.gnu.org (full text, mbox):

From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: Leo Famulari <leo <at> famulari.name>
Cc: 47225 <at> debbugs.gnu.org
Subject: Re: bug#47225: QEMU warning about performance
Date: Tue, 06 Apr 2021 17:42:15 -0400

[Message part 1 (text/plain, inline)]

Hi Leo,

Leo Famulari <leo <at> famulari.name> writes:

> While using `guix system vm`, I noticed this warning. I think it's new,
> maybe from the 5.2.0 update?
>
> ------
> qemu-system-x86_64: warning: 9p: degraded performance: a reasonable
> high msize should be chosen on client/guest side (chosen msize is <=
> 8192). See https://wiki.qemu.org/Documentation/9psetup#msize for
> details.
> ------
>
> That web page suggests that we increase the virtio packet size when
> declaring the 9p file-systems, I think in %linux-vm-file-systems of (gnu
> system vm).

The attached patch should fix it (it does for me at least!).

[0001-system-vm-Set-a-larger-value-for-the-msize-option-of.patch (text/x-patch, attachment)]

[Message part 3 (text/plain, inline)]

Thank you for the report,

Maxim

Message #13 received at 47225 <at> debbugs.gnu.org (full text, mbox):

From: Leo Famulari <leo <at> famulari.name>
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Cc: 47225 <at> debbugs.gnu.org
Subject: Re: bug#47225: QEMU warning about performance
Date: Tue, 6 Apr 2021 18:15:19 -0400

On Tue, Apr 06, 2021 at 05:42:15PM -0400, Maxim Cournoyer wrote:
> From c720e68229322e5c38c0321b021e8d6430636111 Mon Sep 17 00:00:00 2001
> From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
> Date: Tue, 6 Apr 2021 17:37:33 -0400
> Subject: [PATCH] system: vm: Set a larger value for the msize option of the 9p
>  file system.
> 
> Fixes <https://issues.guix.gnu.org/47225>.
> 
> * gnu/system/vm.scm (mapping->file-system): Set the msize option to a value of
> 100 MiB (from the default 8 KiB).
> 
> Reported-by: Leo Famulari <leo <at> famulari.name>

Thanks! I'll test and push along with the next kernel update (that's
when I noticed this warning). Feel free to push sooner if you like.

Message #16 received at 47225 <at> debbugs.gnu.org (full text, mbox):

From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: Leo Famulari <leo <at> famulari.name>
Cc: 47225 <at> debbugs.gnu.org
Subject: Re: bug#47225: QEMU warning about performance
Date: Tue, 06 Apr 2021 20:42:38 -0400

[Message part 1 (text/plain, inline)]

Hi Leo!

Leo Famulari <leo <at> famulari.name> writes:

> On Tue, Apr 06, 2021 at 05:42:15PM -0400, Maxim Cournoyer wrote:
>> From c720e68229322e5c38c0321b021e8d6430636111 Mon Sep 17 00:00:00 2001
>> From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
>> Date: Tue, 6 Apr 2021 17:37:33 -0400
>> Subject: [PATCH] system: vm: Set a larger value for the msize option of the 9p
>>  file system.
>> 
>> Fixes <https://issues.guix.gnu.org/47225>.
>> 
>> * gnu/system/vm.scm (mapping->file-system): Set the msize option to a value of
>> 100 MiB (from the default 8 KiB).
>> 
>> Reported-by: Leo Famulari <leo <at> famulari.name>
>
> Thanks! I'll test and push along with the next kernel update (that's
> when I noticed this warning). Feel free to push sooner if you like.

I hope I'm timely; I've made a revised version of the patch, that should
cover more cases (and actually uses 100 MiB rather than 1 MiB :-)).

Thank you,

[0001-system-vm-Set-a-larger-value-for-the-msize-option-of.patch (text/x-patch, attachment)]

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Message #19 received at 47225 <at> debbugs.gnu.org (full text, mbox):

From: Leo Famulari <leo <at> famulari.name>
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Cc: 47225 <at> debbugs.gnu.org
Subject: Re: bug#47225: QEMU warning about performance
Date: Wed, 7 Apr 2021 13:46:23 -0400

[Message part 1 (text/plain, inline)]

On Tue, Apr 06, 2021 at 08:42:38PM -0400, Maxim Cournoyer wrote:
> I hope I'm timely; I've made a revised version of the patch, that should
> cover more cases (and actually uses 100 MiB rather than 1 MiB :-)).

Yes, you're in time :) Thanks for the revised patch.

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Message #24 received at 47225-done <at> debbugs.gnu.org (full text, mbox):

From: Leo Famulari <leo <at> famulari.name>
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Cc: 47225-done <at> debbugs.gnu.org
Subject: Re: bug#47225: QEMU warning about performance
Date: Thu, 8 Apr 2021 15:17:55 -0400

[Message part 1 (text/plain, inline)]

On Tue, Apr 06, 2021 at 08:42:38PM -0400, Maxim Cournoyer wrote:
> I hope I'm timely; I've made a revised version of the patch, that should
> cover more cases (and actually uses 100 MiB rather than 1 MiB :-)).
> 
> Thank you,
> 

> From eb600c4ffbc8016709db9471f9dc0be1d60167a7 Mon Sep 17 00:00:00 2001
> From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
> Date: Tue, 6 Apr 2021 17:37:33 -0400
> Subject: [PATCH] system: vm: Set a larger value for the msize option of the 9p
>  file system.
> 
> Fixes <https://issues.guix.gnu.org/47225>.
> 
> * gnu/system/vm.scm (%default-msize-value): New variable.
> (%linux-vm-file-systems): Use it as the value of the msize option.
> (mapping->file-system): Likewise.
> 
> Reported-by: Leo Famulari <leo <at> famulari.name>

Pushed as bdc96f6e0e7fbf502f368d3381297ec0b75216d7

Thanks!

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