Re: [GIT PULL] adaptive spinning mutexes

[Ingo Molnar <mingo@elte.hu>]

* Ingo Molnar <mingo@elte.hu> wrote:

> Linus,
> 
> Please pull the adaptive-mutexes-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git adaptive-mutexes-for-linus
> 
> We dropped two fresh patches from v11 for the time being: the two debug 
> patches, they had test failures [they triggered mutex debugging false 
> positives].
> 
> So this tree is v10 (which got a lot of testing already) plus Chris's 
> performance patch. It passes all x86 runtime tests here.

Latest performance figures, on a 2-socket 16-way Nehalem test-system, 
running the code above, measured via "test-mutex V 128 10" VFS 
creat+unlink scalability test on tmpfs and ext3:

                              no-spin           spin

 [tmpfs]    avg ops/sec:       291038         392865       (+34.9%)
 [ext3]     avg ops/sec:       283291         435674       (+53.7%)

Those numbers impress the heck out of me, rarely do we have such kind of 
speedups these days, for any established functionality.

We still have the /sys/debug/sched_features tunable under 
CONFIG_SCHED_DEBUG=y, so should this cause any performance regressions 
somewhere, it can be pinned down and blamed back on this change easily, 
without bisection and without rebooting the box.

	Ingo