On Tue, 4 Dec 2007, Ivan Voras wrote:
Krassimir Slavchev wrote:
There is another report for such problems:
http://blog.insidesystems.net/articles/2007/04/09/what-did-i-do-wrong
Of course - FreeBSD 6.x is really bad at SMP where number of CPUs is larger
then about 2 and the loads include much kernel work (e.g. IO, context
switches). Numeric tasks (SSL) don't depend on the kernel and so they scale
ok. See http://people.freebsd.org/~kris/scaling/Scalability%20Update.pdf for
details.
Another issue is interesting in this thread: that apparently 7.0 also has a
well defined workload where it fails.
There are several known contention points that are high on the list of targets
for the 8-CURRENT branch, some hopefully with MFCs in time for 7.1. These
include contention on the tcbinfo lock, which protects global TCP data
structures, and route table locking, which can affect high packets-per-second
transmission on multiple CPUs at a time. lockmgr is high on the list for
optimization also, especially since it's an older-style sleep lock constructed
out of a mutex and msleep. When we optimized file descriptor locking in 7
(which mostly impacted threaded applications, and was one of the primary
sources of improvement for MySQL), it had a very similar construction as
lockmgr currently has, and optimization made a very big difference.
Robert N M Watson
Computer Laboratory
University of Cambridge
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