Notes on SMP performance on FreeBSD

Since the conclusion of the SMPng project, the focus of SMP development in FreeBSD has shifted from deploying locking infrastructure to careful profiling and optimization of kernel SMP strategies for increased performance on common workloads. FreeBSD 7.0 was the first release to benefit from this optimization work.

Workloads

We are in the process of gathering a library of common application workloads that are used to compare performance across time and against other operating systems. Comparisons are mostly performed against various versions of FreeBSD, Linux 2.6.x systems, and other operating systems. Solaris is a future target of interest, but is not currently available on our test systems.

MySQL sysbench
PgSQL sysbench
Memory allocator performance with the ebizzy benchmark
BIND 9.4 authoritative server
BIND 9.4 recursive server
SPECjbb2005 (java)
Performance comparisons to FreeBSD 4.11 and Dragonfly BSD 1.12

Some of the above benchmarks have not been written up, but there are various unsorted graphs to be found here.

Hardware

Most SMP scaling work is done on 8-core opteron or xeon systems, running in either i386 or amd64 mode. Changes that have the potential for increased overhead are also validated on systems with fewer CPUs, including UP, UP + HTT and dual-core systems, or the 8-core systems with some cores disabled. An intel 16-core xeon is available but requires further scheduler work to improve performance (this work is in progress). Update: this work is largely complete but the 16-core system broke; we are in need of a replacement.

Presentations about FreeBSD performance

The following are some presentations I have given at previous conferences and developer summits relating to FreeBSD SMP performance.

"FreeBSD 7.0 and Beyond", presented at FOSDEM 2008 (Brussels). This is partly a cut down version of the following presentation but contains new performance data
"Introducing FreeBSD 7.0", presented at BSDCon Turkey 2007 (Istanbul) and MeetBSD 2007 (Warsaw, Poland)
"Scalability update", presented at BSDCan 2007 DevSummit. Progress in SMP performance and scalability as of May 2007.
"Filesystem performance", presented at BSDCan 2006 (Ottawa). Report on progress on filesystem performance and scalability in FreeBSD 6.x compared to 4.x and 5.x.

Work in progress

buffer cache (Jeff Roberson)
vm optimizations (Google SoC 2008)
scheduler optimizations for 16-core and 32-core systems (Jeff Roberson)
UDP performance (in progress)
TCP PCB locking (Robert Watson)
...

Last updated 04 June 2008