Date: Mon, 31 Oct 2016 12:19:16 -0600 (MDT)
From: Thomas Gleixner <tglx@linutronix.de>
To: Fengguang Wu <fengguang.wu@intel.com>
cc: Ye Xiaolong <xiaolong.ye@intel.com>, Russ Anderson <rja@sgi.com>,
        Dimitri Sivanich <sivanich@sgi.com>,
        Matt Fleming <matt@codeblueprint.co.uk>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>, Mike Travis <travis@sgi.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Alex Thorlton <athorlton@sgi.com>,
        lkp@01.org
Subject: Re: [LKP] [lkp] [x86/platform/UV] 71854cb812: will-it-scale.per_thread_ops
 -2.3% regression
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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