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

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Date:   Thu, 20 Oct 2016 16:32:10 +0200
From:   Jörg Otte <jrg.otte@...il.com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Michal Marek <mmarek@...e.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Ming Lei <tom.leiming@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [4.9-rc1] Build-time 2x slower

2016-10-20 13:14 GMT+02:00 Rafael J. Wysocki <rjw@...ysocki.net>:
> On Thursday, October 20, 2016 09:57:45 AM Jörg Otte wrote:
>> 2016-10-19 22:55 GMT+02:00 Rafael J. Wysocki <rjw@...ysocki.net>:
>> > 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).
>> >
>>
>> I first tried the merge but git said I'm already uptodate (my tree
>> is at 1a1891d Merge tag 'for-f2fs-4.9-rc2' of
>> git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs already)
>>
>> Then I did the revert of 899bb6642f2a and
>> that worked fine for me.
>
> OK, thanks!
>
> Pointer arithmetics is messed up in that commit somewhat which may be the
> reason for what you see.
>
> Please check if this patch helps (instead of the revert):
>
> https://patchwork.kernel.org/patch/9379639/
>
Yes, works well for me.

Thanks, Jörg