Issue #14718 has been updated by noahgibbs (Noah Gibbs).


On Ubuntu Linux, with Rails Ruby Bench, jemalloc gives an overall speedup (not just memory, end-to-end speedup) of around 11%. Details: "http://engineering.appfolio.com/appfolio-engineering/2018/2/1/benchmarking-rubys-heap-malloc-tcmalloc-jemalloc"

Rails Ruby Bench is basically a big simulated concurrent workload for Discourse. So I think it's fair to say that jemalloc speeds up Discourse by around 11%.

Some of that may be jemalloc's memory savings allowing better caching. I don't have an easy way to measure direct malloc speedup vs better caching.


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Feature #14718: Use jemalloc by default?
https://bugs.ruby-lang.org/issues/14718#change-71696

* Author: mperham (Mike Perham)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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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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