linux-kernel - Re: [lkp-robot] [x86/mm] c4c3c3c2d0: will-it-scale.per_process

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Message-ID: <CALCETrWc1EMGihfKJMqZarbAhrOOjdhgsmpNtPHOrXndTyw19w@mail.gmail.com>
Date:   Tue, 17 Oct 2017 15:06:33 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Ye Xiaolong <xiaolong.ye@...el.com>,
        Markus Trippelsdorf <markus@...ppelsdorf.de>,
        Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Adam Borowski <kilobyte@...band.pl>,
        Brian Gerst <brgerst@...il.com>,
        Johannes Hirte <johannes.hirte@...enkhaos.de>, LKP <lkp@...org>
Subject: Re: [lkp-robot] [x86/mm] c4c3c3c2d0: will-it-scale.per_process_ops
 -61.0% regression

On Tue, Oct 17, 2017 at 1:00 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Tue, Oct 17, 2017 at 06:57:43AM +0200, Markus Trippelsdorf wrote:
>> On 2017.10.16 at 18:06 -0700, Andy Lutomirski wrote:
>> > On Mon, Oct 16, 2017 at 3:15 AM, Borislav Petkov <bp@...en8.de> wrote:
>> > > On Mon, Oct 16, 2017 at 10:39:17AM +0800, kernel test robot wrote:
>> > >>
>> > >> Greeting,
>> > >>
>> > >> FYI, we noticed a -61.0% regression of will-it-scale.per_process_ops due to commit:
>>
>> I think you are reading this wrong:
>> -61.0% regression means 61.0% improvement.
>
> Well, it has this:
>
> 5b8809deb4b0a77f  c4c3c3c2d00826c88b5c02c20e
> ----------------  --------------------------
>          %stddev      change         %stddev
>              \          |                \
>     448554             -61%     174892        will-it-scale.per_process_ops
>
> Xiaolong, can you first explain what those numbers mean? And how do you
> compute those 61%?

I still don't understand what the numbers mean, but this is a PCID
machine (and it's passed through correctly), so the patch will
certainly cause a regression in a benchmark that involves a lot of
brief idle periods.  This kind of issue is why I like having the
debugfs knob there, at least until the dust settles.

>
> Thx.
>
> --
> Regards/Gruss,
>     Boris.
>
> Good mailing practices for 400: avoid top-posting and trim the reply.