Re: lib/50791: NetBSD's malloc has performance issues

[Andreas Gustafsson <gson%gson.org@localhost>]

The following reply was made to PR lib/50791; it has been noted by GNATS.

From: Andreas Gustafsson <gson%gson.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: lib/50791: NetBSD's malloc has performance issues
Date: Tue, 30 Apr 2019 17:02:13 +0300

 To see if the recent jemalloc update had improved performance, I reran
 my test case from this PR using versions of NetBSD-current from before
 and after the update.  The result was the opposite of what I expected:
 my test case ran more than ten times slower after the update than
 before it.  Most of the difference seems to come from running
 unexpectedly fast before the update, not running unexpectely slow
 after it.
 
 Here's the test case again, with an added -Wno-int-to-pointer-cast
 option which makes compilation run more than 50 times faster (an
 interesting performance anomaly in itself, but outside the scope of
 this PR).
 
   ftp http://www.gson.org/netbsd/bugs/malloc-perf/test.c.gz
   gunzip test.c.gz
   cc -Wno-int-to-pointer-cast test.c
   time ./a.out
 
 Before the jemalloc update (using 2019.01.01.10.09.26 sources):
 
 # time ./a.out
         0.08 real         0.06 user         0.02 sys
 
 After the jemalloc update (using 2019.04.29.12.53.15 sources)
 
 # time ./a.out
         1.33 real         0.68 user         0.65 sys
 
 This is NetBSD/amd64 on
 
   cpu0: Intel(R) Xeon(R) CPU           L5630  @ 2.13GHz, id 0x206c2
 
 -- 
 Andreas Gustafsson, gson%gson.org@localhost