Re: [LKP] [lkp] [x86/platform/UV] 71854cb812: will-it-scale.per_thread_ops -2.3% regression

[Thomas Gleixner]

On Mon, 31 Oct 2016, Fengguang Wu wrote:
> On Fri, Oct 28, 2016 at 12:37:45AM +0200, Thomas Gleixner wrote:
> > I have no explanation for this either, but you really should try to figure
> > out what's going on here.
> 
> Xiaolong, how about doing a small debug patch (a WARN_ONCE() line may
> be enough) to verify whether the code path is executed?
> 
> It'd also help to compare vmlinux according to Thomas' reasoning:
> 
> > The only difference between plain rc1 and rc + this patch is the resulting
> > text size and therefor some other unrelated stuff moving to different
> > places in memory which has some yet to figure out side effects.

So one other thing you might try is using rc3 as a base line and then
revert the patch in question on top of rc3 and see whether that weird
behaviour persists.
 
> > From bisect POV, the below graphs show the user_time and system_time
> are clearly and consistently different before/after commit 71854cb812.
> So this commit must impacted something.

I agree. I just have no idea what happens.

Thanks,

	tglx