Jeff Roberson wrote:
On Mon, 31 Mar 2008, David Xu wrote:
davidxu 2008-03-31 02:55:50 UTC
FreeBSD src repository
Modified files:
lib/libthr/thread thr_cond.c thr_private.h thr_rwlock.c
Log:
Rewrite rwlock to user atomic operations to change rwlock state, this
eliminates internal mutex lock contention when most rwlock operations
are read.
Orignal patch provided by: jeff
Thanks David!
Do you still plan to do kernel side support so we can totally eliminate
the pthread mutex and condvars from rwlock? I have evidence that this
would produce further improvements.
Jeff
I have pure kernel version working, sometimes locking kernel sleep
chain is more expensive than a pure userland mutex locking, since
kernel sleep chain lock is global. I am hestiate adding more code
to kernel since I have tested mysql super-smack and sysbench
read-only and seen no visible performance differences.
all patches are here:
http://people.freebsd.org/~davidxu/patch/libthr_umtx_rwlock.diff
http://people.freebsd.org/~davidxu/patch/umtx_rwlock.diff
Te main bottleneck is in mysql itself, there are lots of lock
contention, the following is a list of the main contention points when
testing super-smack read benchmark.
http://people.freebsd.org/~davidxu/mysql/mysql_lock.txt
I don't think it scales beyond 4 cores ( I have tested it on a 4-core
machine).
Regards,
David Xu
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