GNU bug report logs - #79346
igc: PolicyShouldCollectWorld

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From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
To: Helmut Eller <eller.helmut <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 79346 <at> debbugs.gnu.org
Subject: bug#79346: igc: PolicyShouldCollectWorld
Date: Thu, 04 Sep 2025 05:14:49 +0200

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

Eli Zaretskii <eliz <at> gnu.org> writes:

>> From: Helmut Eller <eller.helmut <at> gmail.com>
>> Date: Sun, 31 Aug 2025 11:21:41 +0200
>> 
>> On Sun, Aug 31 2025, Eli Zaretskii wrote:
>> 
>> >> It looks like the bug is in ArenaStep: it should divide the by
>> >> clocks_per_second before calling PolicyShouldCollectWorld.
>> >
>> > What does this affect in Emacs?
>> 
>> This affects how often MPS begins opportunistic GC, i.e. it affects only
>> sessions where igc-step-interval > 0.
>> 
>> Because of the bug, full collections are started more frequently because
>> availableTime > collectionTime is true more often. (availableTime is
>> 10^6 times bigger than it should be.)
>> 
>> The documentation of PolicyShouldCollectWorld says that it starts a full
>> collection only if it expects that the full collection can be completed
>> within availableTime (= igc-step-interval) and if enough time (= per
>> process time) has passed since the last full collection.
>> 
>> > And is this relevant to using a non-debug build of the library?
>> 
>> Yes.
>
> OK, thanks.  I guess it will be interesting to see what happens if
> people use a patched MPS with this bug fixed.

Good find, Helmut. There used to be a comment in arena_step wondering
what's going on, but it got removed, apparently. Does this look right?

[0001-Fix-bug-calculating-available-time-in-ArenaStep.patch (text/x-patch, attachment)]

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