Issue #14759 has been updated by Eregon (Benoit Daloze).


normalperson (Eric Wong) wrote:
>  We will probably match arenas to Guild count dynamically;
>  depending on whether the program uses Guilds or not.
>
>  glibc checks arena_max whenever a new thread allocates memory
>  for the first time, so arena_max doesn't need to be frozen at
>  Ruby startup.

Ah, great to know! I have no objection then.
 
>  I don't know about ko1's timeline, but glibc releases every
>  6 months (Aug and Feb); and Carlos's willingness to accept
>  URCU use in glibc is increasing my interest in contributing
>  to glibc to fix malloc problems for all GNU users :>

It sounds like there is lots of potential there :)

----------------------------------------
Feature #14759: [PATCH] set M_ARENA_MAX for glibc malloc
https://bugs.ruby-lang.org/issues/14759#change-73287

* Author: normalperson (Eric Wong)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
Not everybody benefits from jemalloc and the extra download+install
time is not always worth it.  Lets make the user experience for
glibc malloc users better, too.

Personally, I prefer using M_ARENA_MAX=1 (via MALLOC_ARENA_MAX
env) myself, but there is currently a performance penalty for
that.


gc.c (Init_GC): set M_ARENA_MAX=2 for glibc malloc

glibc malloc creates too many arenas and leads to fragmentation.
Given the existence of the GVL, clamping to two arenas seems
to be a reasonable trade-off for performance and memory usage.

Some users (including myself for several years, now) prefer only
one arena, now, so continue to respect users' wishes when
MALLOC_ARENA_MAX is set.

Thanks to Mike Perham for the reminder [ruby-core:86843]


This doesn't seem to conflict with jemalloc, so it should be safe
for all glibc-using systems.


---Files--------------------------------
0001-gc.c-Init_GC-set-M_ARENA_MAX-2-for-glibc-malloc.patch (1.46 KB)


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