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Message-ID: <alpine.DEB.2.20.1610311216520.10522@nanos>
Date: Mon, 31 Oct 2016 12:19:16 -0600 (MDT)
From: Thomas Gleixner <tglx@...utronix.de>
To: Fengguang Wu <fengguang.wu@...el.com>
cc: Ye Xiaolong <xiaolong.ye@...el.com>, Russ Anderson <rja@....com>,
Dimitri Sivanich <sivanich@....com>,
Matt Fleming <matt@...eblueprint.co.uk>, x86@...nel.org,
LKML <linux-kernel@...r.kernel.org>,
Mike Travis <travis@....com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Alex Thorlton <athorlton@....com>, lkp@...org
Subject: Re: [LKP] [lkp] [x86/platform/UV] 71854cb812: will-it-scale.per_thread_ops
-2.3% regression
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
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