Issue #14718 has been updated by jeremyevans0 (Jeremy Evans).


mperham (Mike Perham) wrote:
> Results, it shows a significant reduction in RSS when run with jemalloc or MALLOC_ARENA_MAX=2.
> 
> ~~~
> > MALLOC_ARENA_MAX=2 /root/versions/2.5.1/bin/ruby -v frag.rb
> 
> ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
>  '--disable-install-doc' '--prefix=/root/versions/2.5.1'
> Total string size: 1917MB
> VmRSS:	 2311052 kB
> 
> > /root/versions/2.5.1j/bin/ruby -v frag.rb
> 
> ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
>  '--with-jemalloc' '--disable-install-doc' '--prefix=/root/versions/2.5.1j'
> Total string size: 1908MB
> VmRSS:	 2306372 kB
> ~~~

I'm not sure what the performance differences are, but looking purely at the memory usage, a 0.2% difference in memory between jemalloc and glibc with MALLOC_ARENA_MAX=2 seems insubstantial.  Certainly if the memory difference is that small, absent significant performance advantages, arguments for bundling jemalloc with ruby or downloading it at configure/make time don't make much sense, compared to just setting M_ARENA_MAX=2 if glibc is being used.

----------------------------------------
Feature #14718: Use jemalloc by default?
https://bugs.ruby-lang.org/issues/14718#change-72054

* 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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