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bug#65700: time when gcs-done is updated needs to be clarified
From: |
Stefan Monnier |
Subject: |
bug#65700: time when gcs-done is updated needs to be clarified |
Date: |
Thu, 07 Sep 2023 09:38:35 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) |
>> I wrote a function which runs each time Emacs collects garbage, so I
>> added it to `post-gc-hook'.
>>
>> That function cares about the value of `gcs-done' and the value of
>> `gc-elapsed'. But it seems that `gcs-done' is updated after
>> `post-gc-hook' is executed?
Indeed, from what I see in the code, `gc-elapsed` and `gcs-done` are
updated *after* running `post-gc-hook`.
This means for example that the time to run `post-gc-hook` is included
in the `gc-elapsed` time.
>> Is this an intended behavior?
Good question. AFAICT this was added by the following commit:
commit 2c5bd60800ce4f2702f263eda2145be342208ffe
Author: Dave Love <fx@gnu.org>
Date: Thu Jan 30 14:15:58 2003 +0000
(Vgc_elapsed, gcs_done): New variables.
(Fgarbage_collect): Use them.
(init_alloc, syms_of_alloc): Set them up.
diff --git a/src/alloc.c b/src/alloc.c
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -4367,7 +4373,15 @@
if (!NILP (Vpost_gc_hook))
{
int count = inhibit_garbage_collection ();
safe_run_hooks (Qpost_gc_hook);
unbind_to (count, Qnil);
}
-
+
+ /* Accumulate statistics. */
+ EMACS_GET_TIME (t2);
+ EMACS_SUB_TIME (t3, t2, t1);
+ if (FLOATP (Vgc_elapsed))
+ XSETFLOAT (Vgc_elapsed, make_float (XFLOAT_DATA (Vgc_elapsed) +
+ EMACS_SECS (t3) +
+ EMACS_USECS (t3) * 1.0e-6));
+ gcs_done++;
The only related commit I see around that time is the associated NEWS
message:
** New variables `gc-elapsed' and `gcs-done' provide extra information
on garbage collection.
So I strongly suspect that it was largely accidental. "Philosophically",
both choices make sense (either consider `post-gc-hook` as being part of
the GC or consider it as external to the GC).
I'd be curious to know how it affects your code.
Stefan
- bug#65700: time when gcs-done is updated needs to be clarified, Shynur Xie, 2023/09/02
- bug#65700: time when gcs-done is updated needs to be clarified, Eli Zaretskii, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified,
Stefan Monnier <=
- bug#65700: time when gcs-done is updated needs to be clarified, Shynur Xie, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Eli Zaretskii, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Shynur Xie, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Stefan Monnier, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Shynur Xie, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Shynur Xie, 2023/09/12
- bug#65700: time when gcs-done is updated needs to be clarified, Stefan Monnier, 2023/09/12
- bug#65700: time when gcs-done is updated needs to be clarified, Stefan Monnier, 2023/09/12
- bug#65700: time when gcs-done is updated needs to be clarified, Stefan Monnier, 2023/09/07
- bug#65700: time when gcs-done is updated needs to be clarified, Eli Zaretskii, 2023/09/07