Switch pfil(9) to rmlocks
max at love2party.net
Fri Nov 23 05:42:49 PST 2007
On Friday 23 November 2007, Robert Watson wrote:
> On Fri, 23 Nov 2007, Max Laier wrote:
> > attached is a diff to switch the pfil(9) subsystem to rmlocks, which
> > are more suited for the task. I'd like some exposure before doing
> > the switch, but I don't expect any fallout. This email is going
> > through the patched pfil already - twice.
> Have you done performance measurements that show rmlocks to be a win in
> this scenario? I did some patchs for UNIX domain sockets to replace
> the rwlock there but it appeared not to have a measurable impact on SQL
> benchmarks, presumbaly because the read/write blend wasn't right and/or
> that wasnt a significant source of overhead in the benchmark. I'd
> anticipate a much more measurable improvement for pfil, but would be
> interested in learning how much is seen?
I don't yet, but will see if I can collect some data later today. The
main reason for the switch is shortcomings in rwlock's (not)
implementation of reader recursion as discussed in -arch "rwlocks,
correctness over speed." rmlocks do that correctly, afaiu.
Unless an artificial no-op hook is used, I don't expect to see significant
performance gain, however. All current pfil(9) consumer need some form
of synchronization of their own, which will probably nullify the gain
/"\ Best regards, | mlaier at freebsd.org
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