Re: Progress on scaling of FreeBSD on 8 CPU systems

On Saturday 24 February 2007 1:31 pm, Kris Kennaway wrote:
Now that the goals of the SMPng project are complete, for the past
year or more several of us have been working hard on profiling
FreeBSD in various multiprocessor workloads, and looking for
performance bottlenecks to be optimized.

We have recently made significant progress on optimizing for MySQL
running on an 8-core amd64 system. The graph of results may be found
here:

http://www.freebsd.org/~kris/scaling/scaling.png

This shows the graph of MySQL transactions/second performed by a
multi-threaded client workload against a local MySQL database with
varying numbers of client threads, with identically configured
FreeBSD and Linux systems on the same machine.

The test was run on FreeBSD 7.0, with the latest version of the ULE
2.0 scheduler, the libthr threading library, and an uncommitted patch
from Jeff Roberson [1] that addresses poor scalability of file
descriptor locking (using a new sleepable mutex primitive); this
patch is responsible for almost all of the performance and scaling
improvements measured. It also includes some other patches
(collected in my kris-contention p4 branch) that have been shown to
help contention in MySQL workloads in the past (including a UNIX
domain socket locking pushdown patch from Robert Watson), but these
were shown to only give small individual contributions, with a
cumulative effect on the order of 5-10%.

With this configuration we are able to achieve performance that is
consistent with Linux at peak (the graph shows Linux 2% faster, but
this is commensurate with the margin of error coming from variance
between runs, so more data is needed to distinguish them), with 8
client threads (=1 thread/CPU core), and significantly outperforms
Linux at higher than peak loads, when running on the same hardware.

Specifically, beyond 8 client threads FreeBSD has only minor
performance degradation (an 8% drop from peak throughput at 8 clients
to 20 clients), but Linux collapses immediately above 8 threads, and
above 14 threads asymptotes to essentially single-threaded levels.
At 20 clients FreeBSD outperforms Linux by a factor of 4.

We see this result as part of the payoff we are seeing from the hard
work of many developers over the past 7 years. In particular it is a
significant validation of the SMP and locking strategies chosen for
the FreeBSD kernel in the post-FreeBSD 4.x world.

More configuration details and discussion about the benchmark may be
found here:

http://people.freebsd.org/~kris/scaling/mysql.html

Well done! Nice work guys!!! FYI, we're working with Intel to get an
engineering sample of the quad core, quad CPU system for some further
SMP testing. Kris, I'll let you know as soon as I have word when we're
getting one and if we can keep it, we'll send it up to be included in
the cluster in Canada.

Yay!!!!!!! This is just fabulous.

-matt

Kris

--
Matt Olander
CTO, iXsystems - "Servers for Open Source" http://www.iXsystems.com
Public Relations, The FreeBSD Project http://www.FreeBSD.org
BSD on the Desktop! http://www.pcbsd.org
Phone: (408)943-4100 ext. 113 Fax: (408)943-4101
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