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Groups > linux.kernel > #1503240
| From | Linus Torvalds <torvalds@linux-foundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [4.9-rc1] Build-time 2x slower |
| Date | 2016-10-18 19:20 +0200 |
| Message-ID | <stGdr-4O9-29@gated-at.bofh.it> (permalink) |
| References | <stiEa-5Hd-13@gated-at.bofh.it> <strxL-3nR-7@gated-at.bofh.it> <stz2h-8dA-3@gated-at.bofh.it> <stFU5-4q4-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Oct 18, 2016 at 9:49 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
> On Tue, Oct 18, 2016 at 12:04 AM, Sedat Dilek <sedat.dilek@gmail.com> wrote:
>>
>> not sure whom to address on this issue.
>>
>> I have built Linux v4.9-rc1, v4.8.2 and v4.4.25 kernels (in this
>> order) this morning.
>>
>> Building a Linux v4.8.2 under Linux v4.9-rc1 took two times longer.
>>
>> As usually I build with 2 parallel-make-jobs.
>> This takes approx. 30mins.
>> Under Linux v4.9-rc1 it took approx. an hour.
>>
>> My system is a Ubuntu/precise AMD64 (WUBI installation).
>> I use my normal build-environment.
>
> I can confirm the problem. I use 3 build jobs in parallel
> and the kernel build takes 2,5 times longer.
>
> I'm only seeing 1 (of 4) cores are running with max frequency.
> The other are running in minimum frequency. And this seems not
> to be limited to build jobs however.
>
> The last known good kernel for me is ..-4.8.0-14604-g29fbff8
Well, there are a few merges in 4.9-rc1 since that
4.8.0-14604-g29fbff8 version, but the obvious ones are my pulls from:
Michal Marek (2):
kbuild updates
misc kbuild changes
(My merge commit ID's are 50cff89837a4 and 84d69848c97f) with
everything else looking like "normal code updates".
Michal: a 2.5x slowdown of the kernel build was presumably *not* intentional.
I'm not seeing anything obvious, but if it's spending a lot more time
in fixdep, then it's that "strstr()" change. That commit seems to
assume that strstr() is fast, which is a debatable assumption and
might be wrong in some environments.
But even with a "strstr()" written by a sloth that was dropped on its
head a few too many times when young, I can't see it being *that* much
slower.
Can you do just a silly
perf record make -j8
of the bad build, and see if something stands out when you do "perf report"?
But maybe Michal has some ideas.
Linus
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Re: [4.9-rc1] Build-time 2x slower Ming Lei <tom.leiming@gmail.com> - 2016-10-18 03:40 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-18 11:40 +0200
Re: [4.9-rc1] Build-time 2x slower Jörg Otte <jrg.otte@gmail.com> - 2016-10-18 19:00 +0200
Re: [4.9-rc1] Build-time 2x slower Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-18 19:20 +0200
Re: [4.9-rc1] Build-time 2x slower Jörg Otte <jrg.otte@gmail.com> - 2016-10-19 17:30 +0200
Re: [4.9-rc1] Build-time 2x slower Linus Torvalds <torvalds@linux-foundation.org> - 2016-10-19 17:30 +0200
Re: [4.9-rc1] Build-time 2x slower Jörg Otte <jrg.otte@gmail.com> - 2016-10-19 19:00 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-19 22:50 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 09:50 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-20 13:10 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-20 16:30 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 16:40 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-20 16:50 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-21 03:00 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 16:30 +0200
Re: [4.9-rc1] Build-time 2x slower Jörg Otte <jrg.otte@gmail.com> - 2016-10-20 10:00 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 10:10 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-20 13:10 +0200
Re: [4.9-rc1] Build-time 2x slower Jörg Otte <jrg.otte@gmail.com> - 2016-10-20 16:40 +0200
Re: [4.9-rc1] Build-time 2x slower "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-10-20 16:50 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 09:30 +0200
Re: [4.9-rc1] Build-time 2x slower Sedat Dilek <sedat.dilek@gmail.com> - 2016-10-20 09:50 +0200
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