Messages in this thread | | | Date | Mon, 7 Sep 2015 09:32:26 +1000 | From | Dave Chinner <> | Subject | Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression |
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On Fri, Sep 04, 2015 at 05:25:23PM +0200, Peter Zijlstra wrote: > Something like so... > > --- > Subject: locking: Fix virt test-and-set lock implementation > > Dave ran into horrible performance on a VM without PARAVIRT_SPINLOCKS > set and Linus noted that the test-and-set implementation was retarded. > > One should spin on the variable with a load, not a rmw. > > While there, remove the queued from the name, as the lock isn't queued > at all, but a simple test-and-set. > > Reported-by: Dave Chinner <david@fromorbit.com> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
FSUse% Count Size Files/sec App Overhead 0 1600000 0 319511.8 9398733 0 3200000 0 301517.9 9516230 0 4800000 0 300357.6 9676651 0 6400000 0 282167.8 11513255
Looks OK.
Tested-by: Dave Chinner <david@fromorbit.com>
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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