Messages in this thread | | | Date | Wed, 09 Sep 2015 22:01:54 -0400 | From | Waiman Long <> | Subject | Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression |
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On 09/04/2015 01:48 AM, Dave Chinner wrote: > Hi Waiman, > > For the first time in months I just turned of spinlock debugging on > my performance test machine and I just got an unpleasant surprise on > my standard inode allocation and reclaim test. I've described this > test to you before, because it's found regressions in your previous > lock scaling changes: > > http://permalink.gmane.org/gmane.linux.kernel/1768786 > > This time it is the fsmark run that I use to populate the filesystem > that is demonstrating a locking regression. I'll asked you before > if you could add this test to your lock scaling regression test > suite; please do it this time. > > Now, the regression. With spinlock debugging turned on, the > performance of my usual XFS inode allocation benchmark using fsmark > reports performance like this: > > FSUse% Count Size Files/sec App Overhead > 0 1600000 0 312594.0 9944159 > 0 3200000 0 295668.6 10399679 > 0 4800000 0 279026.1 11397617 > ..... > > This has been pretty stable for several releases - it varies +/- a > few percent, but it's pretty much been like this since about 3.2 > when CONFIG_XFS_DEBUG=n, with or without basic spinlock debugging. > > When I turned spinlock debugging off on 4.2 to get some perf numbers > a request from Linus, I got this: > > FSUse% Count Size Files/sec App Overhead > 0 1600000 0 114143.9 9597599 > 0 3200000 0 95486.9 9460413 > 0 4800000 0 93918.2 9784699 > .
I am sorry that I was on vacation over the past weekend and so was not able to respond in a timely manner. As Peter already has a patch to address the root cause of this problem. I think this problem is all set.
Cheers, Longman
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