GNU logs - #39361, boring messages

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Subject: bug#39361: continuation and gc performance
Resent-From: Stefan Israelsson Tampe <stefan.itampe@HIDDEN>
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From: Stefan Israelsson Tampe <stefan.itampe@HIDDEN>
Date: Thu, 30 Jan 2020 22:10:50 +0100
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I think I found a gc leak in guile 3.0

Isn't it so that so the continuation keep a copy of the stack. The issue is
that in the stack a raw integer or float may be present and so the gc
properties is less then ideal as those may be interpreted as pointers by
the GC and lead to parts of the heap being kept from garnage collecting.

The information about a slot being a raw value or a scm value is
available as we do the correct gc updating of the stack inside guile 3.0.
May I propose that we add a bitvector to the continuation that indicate
that if a lslot is raw or not. Then add a pass that collect the rawness
information in the creation of the closure. Finally a custom made mark
procedure for closures can be made that uses all this information to make
sure to mark only scm slots in the stored continuation therby improving gc
perfromance.

With this information it would also be possible to serialize continuations
even if they have slots that are raw values.

Happy Hacking

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<div dir=3D"ltr"><div class=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail=
_attr"><br></div><div dir=3D"ltr"><div>I think I found a gc leak in guile 3=
.0</div><div><br></div><div>Isn&#39;t it so that so the continuation keep a=
 copy of the stack. The issue is that in the stack a raw integer or float m=
ay be present and so the gc properties is less then ideal as those may be i=
nterpreted as pointers by the GC and lead to parts of the heap being kept f=
rom garnage collecting.</div><div><br></div><div>The information about a sl=
ot being a raw value or a scm value is available=C2=A0as we do the correct =
gc updating of the=C2=A0stack inside guile 3.0. May I propose that we add a=
 bitvector to the continuation that indicate that if a lslot is raw or not.=
 Then add a pass that collect the rawness information in the creation of th=
e closure. Finally a custom made mark procedure for closures can be made th=
at uses all this information to make sure to mark only scm slots in the sto=
red continuation therby improving gc perfromance.</div><div><br></div><div>=
With this information it would also be possible to serialize continuations =
even if they have slots that are raw values.</div><div><br></div><div>Happy=
 Hacking</div><div>=C2=A0</div></div>
</div></div>

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From: help-debbugs@HIDDEN (GNU bug Tracking System)
To: Stefan Israelsson Tampe <stefan.itampe@HIDDEN>
Subject: bug#39361: Acknowledgement (continuation and gc performance)
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Subject: bug#39361: continuation and gc performance
Resent-From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@HIDDEN>
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To: Stefan Israelsson Tampe <stefan.itampe@HIDDEN>
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From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@HIDDEN>
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 (Stefan Israelsson Tampe's message of "Thu, 30 Jan 2020 22:10:50
 +0100")
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Hi Stefan,

Stefan Israelsson Tampe <stefan.itampe@HIDDEN> skribis:

> I think I found a gc leak in guile 3.0
>
> Isn't it so that so the continuation keep a copy of the stack. The issue =
is
> that in the stack a raw integer or float may be present and so the gc
> properties is less then ideal as those may be interpreted as pointers by
> the GC and lead to parts of the heap being kept from garnage collecting.
>
> The information about a slot being a raw value or a scm value is
> available as we do the correct gc updating of the stack inside guile 3.0.
> May I propose that we add a bitvector to the continuation that indicate
> that if a lslot is raw or not. Then add a pass that collect the rawness
> information in the creation of the closure. Finally a custom made mark
> procedure for closures can be made that uses all this information to make
> sure to mark only scm slots in the stored continuation therby improving gc
> perfromance.

I believe what you describe is already what happens in
=E2=80=98scm_i_vm_mark_stack=E2=80=99.  Or am I missing something?

Thanks,
Ludo=E2=80=99.

Last modified: Sat, 21 Mar 2020 17:45:01 UTC

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