From: dennisb55@...
Date: 2018-05-10T05:37:01+00:00
Subject: [ruby-core:86964] [Ruby trunk Feature#14718] Use jemalloc by	default?

Issue #14718 has been updated by bluz71 (Dennis B).


normalperson (Eric Wong) wrote:
> mperham@gmail.com wrote:
>  > https://bugs.ruby-lang.org/issues/14718
>  
>  Agreed.  I think it's acceptable to enable jemalloc by default short-term.

I actually believe if enabled it would for the long-term.

>  Long-term (unlikely this year) I hope to work with glibc team to
>  improve malloc on their end.  I have ideas which require LGPL
>  code (wfcqueue) to implement, so not doable with jemalloc.

This is admirable, but we are still talking about years away. 2021 before in a Linux LTS release?

The fundamentals of the glibc allocator derive from the ptmalloc2 allocator of the 1990s, which in turn builds upon the work of Doug Lea's allocators from the late 80s and early 90s. The fundamental core of glibc's allocator is decades old. It is not surprising that even today it still has real problems with memory fragmentation, it is fundamentally old.

I doubt whether the glibc allocator could compete with jemalloc in regards to memory fragmentation in combination with multiple-Guilds.

P.S. I do use jemalloc with Ruby and the results mirror what Mike has seen, it is a Ruby game-changer; probably more-so than even a JIT.

----------------------------------------
Feature #14718: Use jemalloc by default?
https://bugs.ruby-lang.org/issues/14718#change-71929

* Author: mperham (Mike Perham)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
I know Sam opened #9113 4 years ago to suggest this but I'm revisiting the topic to see if there's any movement here for Ruby 2.6 or 2.7.  I supply a major piece of Ruby infrastructure (Sidekiq) and I keep hearing over and over how Ruby is terrible with memory, a huge memory hog with their Rails apps.  My users switch to jemalloc and a miracle occurs: their memory usage drops massively.  Some data points:

https://twitter.com/brandonhilkert/status/987400365627801601
https://twitter.com/d_jones/status/989866391787335680
https://github.com/mperham/sidekiq/issues/3824#issuecomment-383072469

Redis moved to jemalloc many years ago and it solved all of their memory issues too.  Their conclusion: the glibc allocator "sucks really really hard". http://oldblog.antirez.com/post/everything-about-redis-24.html

This is a real pain point for the entire Rails community and would improve Ruby's reputation immensely if we can solve this problem.



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