From: Eric Wong <normalperson@...>
Date: 2018-05-21T06:30:10+00:00
Subject: [ruby-core:87211] Re: [Ruby trunk Feature#14759] [PATCH] set M_ARENA_MAX for glibc malloc

mame@ruby-lang.org wrote:
> I tried to change Mike's script to use I/O, and I've created a
> script that works best with glibc with no MALLOC_ARENA_MAX
> specified.

Interesting, you found a corner case of some fixed sizes where
the glibc default appears the best.

I tested 16K instead of 64K since my computer is too slow
and 16K is the default buffer size for IO.copy_stream,
net/protocol, etc...) and the default was still best
in that case.

So, I wonder if there is a trim threshold where this happens
and multiple arenas tickles the threshold more frequently.

However, I believe Mike's script of random sizes is more
representative of realistic memory use.  Unfortunately,
srand+rand alone is not enough to give consistently reproducible
results for benchmarking with threads...

Maybe a single thread needs to generate all the random numbers
and feed them round-robin to per-thread SizedQueue for
deterministic results.

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