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Re: Default threads value in OpenLDAP
--On Wednesday, April 18, 2007 1:43 PM -0700 Howard Chu <firstname.lastname@example.org>
Quanah Gibson-Mount wrote:
After extensive benchmarking by both Howard & I, it seems the default
value for the threads setting in OpenLDAP (16) is excessive for most
hardware. Unless someone has plenty of CPUs (at least 4+, not counting
fake HT CPUs), slapd performance is significantly improved by running
at 8 threads. Recent tests done by Howard indicated that dropping the
number of threads to 4 on my 2 CPU boxes further improved read
performance, but I haven't had the time to do the corresponding write
performance tests to see how they were impacted. In any case, the "8"
value is definitely better for both read & write performance for 1 & 2
CPU servers (and possibly 4, I just haven't had one to experiment on).
The only time I've found a need to increase the number of threads was
when I was benchmarking the Sun T2000, which had 32 cores. Given all
of this, I'd like to propose that we change
in slap.h from 16 to 8 for OpenLDAP 2.4.
I think we should leave this alone until we have read/write test results
to confirm things. Also, our testing was primarily on Linux 2.6; other
platforms may have more efficient thread scheduling.
I reached the same conclusions on my old Solaris V120's, with RW tests too.
;) If we get that build farm proposal, that might be a good opportunity to
do some testing of small DB's on a variety of platforms, I suppose.
However, I'm guessing the majority of OpenLDAP users fall into the Linux
and Solaris categories.
Senior Systems Software Developer
ITS/Shared Application Services
GnuPG Public Key: http://www.stanford.edu/~quanah/pgp.html