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 <da...@fromorbit.com>
> Suggested-by: Linus Torvalds <torva...@linux-foundation.org>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@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 <da...@fromorbit.com>
Cheers,
Dave.
--
Dave Chinner
da...@fromorbit.com
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