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; Update documentation of GC in ELisp manual

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* doc/lispref/internals.texi (Garbage Collection): Update default
values for GC-related thresholds.  (Bug#79074)
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Eli Zaretskii 2025-07-28 16:14:44 +03:00
parent 57a9798c22
commit 8ec2ddebdd
1 changed files with 15 additions and 10 deletions
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doc/lispref/internals.texi
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@ -555,16 +555,17 @@ object type; space allocated to the contents of buffers does not count.
The initial threshold value is @code{GC_DEFAULT_THRESHOLD}, defined in The initial threshold value is @code{GC_DEFAULT_THRESHOLD}, defined in
@file{alloc.c}. Since it's defined in @code{word_size} units, the @file{alloc.c}. Since it's defined in @code{word_size} units, the
value is 400,000 for the default 32-bit configuration and 800,000 for value is 400,000 for the default 32-bit configuration, and 800,000 for
the 64-bit one. If you specify a larger value, garbage collection the 64-bit one and for 32-bit builds configured with the
will happen less often. This reduces the amount of time spent garbage @option{--with-wide-int} option. If you specify a larger value, garbage
collecting (so Lisp programs will run faster between cycles of garbage collection will happen less often. This reduces the amount of time
collection that happen more rarely), but increases total memory use. spent garbage collecting (so Lisp programs will run faster between
You may want to do this when running a program that creates lots of cycles of garbage collection that happen more rarely), but increases
Lisp data, especially if you need it to run faster. However, we total memory use. You may want to do this when running a program that
recommend against increasing the threshold for prolonged periods of creates lots of Lisp data, especially if you need it to run faster.
time, and advise that you never set it higher than needed for the However, we recommend against increasing the threshold for prolonged
program to run in reasonable time. Using thresholds higher than periods of time, and advise that you never set it higher than needed for
the program to run in reasonable time. Using thresholds higher than
necessary could potentially cause higher system-wide memory pressure, necessary could potentially cause higher system-wide memory pressure,
and also make each garbage-collection cycle take much more time, and and also make each garbage-collection cycle take much more time, and
should therefore be avoided. should therefore be avoided.
@ -585,6 +586,10 @@ As the heap size increases, the time to perform a garbage collection
increases. Thus, it can be desirable to do them less frequently in increases. Thus, it can be desirable to do them less frequently in
proportion. proportion.
The initial percentage value is 0.1 in interactive sessions and while
dumping Emacs (@pxref{Building Emacs}), and 1.0 in non-interactive
(a.k.a.@: ``batch'') sessions.
As with @code{gc-cons-threshold}, do not enlarge this more than As with @code{gc-cons-threshold}, do not enlarge this more than
necessary, and never for prolonged periods of time. necessary, and never for prolonged periods of time.
@end defopt @end defopt