linux-kernel - Re: [4.9-rc1] Build-time 2x slower

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Message-ID: <CA+icZUXVGChLViAH8vsmP1W3P4KnF4+dCQKqaGsZe+DTHbrA5Q@mail.gmail.com>
Date:   Thu, 20 Oct 2016 09:41:34 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Jörg Otte <jrg.otte@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Michal Marek <mmarek@...e.com>,
        Ming Lei <tom.leiming@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [4.9-rc1] Build-time 2x slower

On Wed, Oct 19, 2016 at 10:55 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> On Wednesday, October 19, 2016 06:59:35 PM Jörg Otte wrote:
>> 2016-10-19 17:29 GMT+02:00 Linus Torvalds <torvalds@...ux-foundation.org>:
>> > On Wed, Oct 19, 2016 at 4:07 AM, Jörg Otte <jrg.otte@...il.com> wrote:
>> >>
>> >> Additional info: I usally use schedutil governor.
>> >> If I switch to performance governor problems go away.
>> >> Maybe a cpufreq problem?
>> >
>> > Oh, I completely misread the original bug report, and then didn't read
>> > your confirmation email right.
>> >
>> > I thought you had a slower build of the different kernels (when
>> > building on the same kernel), and that the _build_ itself had slowed
>> > down for some reason. But you're actually saying that doing the _same_
>> > build actually takes longer when running on 4.9-rc1.
>>
>> Exactly!
>>
>> Btw: ondemand governor is also good.
>>
>> > There are a few small cpufreq changes there in between commit
>> > 29fbff8698fc (that you reported was fine - please tell me I got _that_
>> > right, at least?) and 4.9-rc1.
>>
>> Perfect! That's what I mean.
>>
>> > Adding Rafael to the cc.
>> >
>> > That said, none of them look all that likely to me. It *would* be good
>> > if you could bisect it a bit (perhaps not fully, but a couple of
>> > bisection steps to narrow down what area it is).
>>
>> I try that tomorrow.
>
> Well, please try commit ef98988ba369 (Merge tag 'pm-extra-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm) which is the
> merge introducing the late cpufreq changes.  If the issue is there, please
> try to revert commit 899bb6642f2a (cpufreq: skip invalid entries when searching
> the frequency) which is the only cpufreq one that may matter for the schedutil
> governor (and I have one fix for that commit queued up already).
>

Is "cpufreq: fix overflow in cpufreq_table_find_index_dl()" the fix
you are speaking of?

Fixes: 899bb6642f2a (cpufreq: skip invalid entries when searching the frequency)

If yes, can you add a hint in the commit message describing the impact
like here a slow-down of building a linux-kernel.
With a reference to this ML-thread?

I try to test this but don't be disappointed if you get no answer.

- Sedat -

[1] https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/commit/?h=linux-next&id=f7a7a80ae30521b65a6dfc98df45d3ec9e238d73
[2] https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/patch/?id=f7a7a80ae30521b65a6dfc98df45d3ec9e238d73