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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
@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
the 64-bit one. If you specify a larger value, garbage collection
will happen less often. This reduces the amount of time spent garbage
collecting (so Lisp programs will run faster between cycles of garbage
collection that happen more rarely), but increases total memory use.
You may want to do this when running a program that creates lots of
Lisp data, especially if you need it to run faster. However, we
recommend against increasing the threshold for prolonged 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
value is 400,000 for the default 32-bit configuration, and 800,000 for
the 64-bit one and for 32-bit builds configured with the
@option{--with-wide-int} option. If you specify a larger value, garbage
collection will happen less often. This reduces the amount of time
spent garbage collecting (so Lisp programs will run faster between
cycles of garbage collection that happen more rarely), but increases
total memory use. You may want to do this when running a program that
creates lots of Lisp data, especially if you need it to run faster.
However, we recommend against increasing the threshold for prolonged
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,
and also make each garbage-collection cycle take much more time, and
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
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
necessary, and never for prolonged periods of time.
@end defopt