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

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Message-ID: <2198826.9suuMCzPZN@vostro.rjw.lan>
Date:   Wed, 19 Oct 2016 22:55:36 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Jörg Otte <jrg.otte@...il.com>
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

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).

Thanks,
Rafael