[ruby-core:105883] [Ruby master Feature#15667] Introduce malloc_trim(0) in full gc cycles

Issue #15667 has been updated by [e-mail] (Bruno Escherl).


Wouldn't that be a good feature in combination with GC auto_compaction? First run the auto_compaction against memory fragmentation and then call malloc_trim to give back the memory?

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Feature #15667: Introduce malloc_trim(0) in full gc cycles
https://bugs.ruby-lang.org/issues/15667#change-94424

* Author: sam.saffron (Sam Saffron)
* Status: Open
* Priority: Normal
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Per Hongli's excellent article it looks like malloc_trim can help tremendously with memory bloat issues. 


https://www.joyfulbikeshedding.com/blog/2019-03-14-what-causes-ruby-memory-bloat.html#a-magic-trick-trimming


I would like to get this patch tested side-by-side at Discourse, GitHub and Shopify. If it looks good I think this is both a great candidate for 2.7 and and 2.4,2.5,2.6 backports. 


Will coordinate with Shopify and GitHub to see if we can get numbers posted here, I will run tests on a live Discourse instance over the next week and report numbers here. 

Koichi, what are your thoughts, to me this looks like an incredibly safe patch, the amount of work added to major GCs is tiny compared to the potential benefit, walking all pages is a very cheap operation.



---Files--------------------------------
ruby_gc_malloc_trim.patch (1011 Bytes)
Screenshot_2019-03-28 Grafana - Compare Discourse Perf.png (530 KB)
crash.png (85.9 KB)


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