From: shevegen@...
Date: 2018-04-27T18:50:55+00:00
Subject: [ruby-core:86734] [Ruby trunk Feature#14718] Use jemalloc by	default?

Issue #14718 has been updated by shevegen (Robert A. Heiler).


I know way too little about the topic at hand, so I can not really
comment on it, the usability, gains and so forth.

I had a look at the discussion at #9113, just due to my curiosity alone.

It seems as if matz has not yet commented on it; perhaps this issue
has not been mentioned yet?

If this is the case, then perhaps the issue here may be a good candidate
for the next ruby-developer meeting. Matz has the "3x as fast" goal, so
this may perhaps add another +0.5% or so? :D

I guess what may be useful to know is if there is some summary or overview
of trade offs for jemalloc by default, like pros and cons. I guess the pros
have been mentioned already (less problems with memory) - are there cons
that speak against the move? For example, by default, linux users
using ruby, would they have to re-compile their ruby to benefit from this?
Are there commandline switches? Questions like that. I am mostly asking
so that information about it, also "trickles downwards" into more casual
ruby hackers too.

Ruby is used by people who don't know that much about the internals 
and may not know the differences between glibc and jemalloc. I myself
know what glibc is but I never really heard of jemalloc before. It's
great if they improved on something though. Are there really no 
disadvantages?

(On a side note, glibc seems to be evolving quite slowly ... reminds
me a bit of GCC versus LLVM but I may be wrong.)

----------------------------------------
Feature #14718: Use jemalloc by default?
https://bugs.ruby-lang.org/issues/14718#change-71689

* 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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