Messages in this thread | | | Date | Sun, 18 Oct 2009 01:06:54 +0200 | From | Nick Piggin <> | Subject | Re: -rt dbench scalabiltiy issue |
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On Fri, Oct 16, 2009 at 06:37:36PM -0700, john stultz wrote: > Additionally looking at the perf data, it does seem the dcache_lock is > the contention point w/ ext2 on -rt13, but with Nick's patch, the > contention still stays mostly in the dput/path_get functions. So it > seems its just been moved rather then eased with _my port_ of Nick's > patch (emphasis on "my port", since with nick's patch against mainline > there is no regression at all.. I don't want to drag Nick's patches > through the mud here :)
No there is nothing to suggest you've done the wrong thing. The dentry refcounting issue was always a known one, and yes looking at the ext3 profiles, ext3/jbd is adding to the refcounting load so it is not surprising that it has slowed down. Also -rt probably has more trouble than mainline when you start hitting spinlock contention.
But before turning it back into an atomic, we need to see how far the lock free path walking stuff goes (and that is not finished yet either).
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