From: dennisb55@... Date: 2018-08-10T05:37:27+00:00 Subject: [ruby-core:88418] [Ruby trunk Feature#14759] [PATCH] set M_ARENA_MAX for glibc malloc Issue #14759 has been updated by bluz71 (Dennis B). Ruby use generally falls into one of two categories: short-lived or very long-lived. For short-lived Ruby scripts MALLOC_ARENA_MAX could, and maybe should, be left as is? For long-lived Ruby processes MALLOC_ARENA_MAX absolutely should be reduced from the glibc default as noted in this request and [#14718](https://bugs.ruby-lang.org/issues/14718). Hopefully, in time glibc can be improved, but that may be many years away. I wonder if a new runtime flag should be added to the Ruby executable, `--long-lived`? That flag could tweak internals to favour long runtimes. For the moment it could tweak `MALLOC_ARENA_MAX`, in the future it could tweak other aspects to favour low memory fragmentation. Rails, Sinatra, Sidekiq users would then be encouraged to invoke Ruby via `ruby --long-lived`? I suspect some/many folks would not like that since that will not be the default behaviour. But that would avoid the weird regression noted above that concerns @shyouhei. Ideally we don't want to penalise short-lived Ruby users for the benefit of long-lived Ruby users. ---------------------------------------- Feature #14759: [PATCH] set M_ARENA_MAX for glibc malloc https://bugs.ruby-lang.org/issues/14759#change-73472 * 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) -- https://bugs.ruby-lang.org/ Unsubscribe: