On Thu, Jul 03, 2014 at 06:54:50PM -0700, Jason Low wrote: > Subject: [PATCH] rwsem: In rwsem_can_spin_on_owner(), return false if no owner > > It was found that the rwsem optimistic spinning feature can potentially > degrade > performance when there are readers. Perf profiles indicate in some workloads > that significant time can be spent spinning on !owner. This is because we > don't > set the lock owner when readers(s) obtain the rwsem. > > In this patch, we'll modify rwsem_can_spin_on_owner() such that we'll return > false if there is no lock owner. The rationale is that if we just entered the > slowpath, yet there is no lock owner, then there is a possibility that a > reader > has the lock. To be conservative, we'll avoid spinning in these situations. > > Dave Chinner found performance benefits with this patch in the xfs_repair > workload, where the total run time went from approximately 4 minutes 24 > seconds, > down to approximately 1 minute 26 seconds with the patch. > > Tested-by: Dave Chinner <dchin...@redhat.com> > Signed-off-by: Jason Low <jason.l...@hp.com>
Davidlohr, you'll be running this through your AIM and other benchmarks, I suppose?
pgpne5Be7JHiK.pgp
Description: PGP signature
