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

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Message-ID: <CA+icZUXot9ve9wWVwgqPukjZmA8BhJ-VxFDR7srxh=K+4CESPQ@mail.gmail.com>
Date:   Tue, 18 Oct 2016 11:30:57 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     Ming Lei <tom.leiming@...il.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [4.9-rc1] Build-time 2x slower

On Tue, Oct 18, 2016 at 3:38 AM, Ming Lei <tom.leiming@...il.com> wrote:
> On Tue, Oct 18, 2016 at 12:04 AM, Sedat Dilek <sedat.dilek@...il.com> wrote:
>> Hi Linus,
>>
>> 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.
>>
>> If you need further informations, please let me know.
>
> Kernel building is more like a CPU-bound workload, so maybe
> some clues can be got by comparing results of 'perf top/record',
> which should be very easy to collect.
>

I have no big experiences with perf.
Last I played was testing early days of "lockdep" feature.
Can you give some clear instructions on how to use perf top/record in
this scenario?

- Sedat -

>>
>> Regards,
>> - Sedat -
>>
>> P.S.: Listing content of attached tarball file.
>>
>> $ LC_ALL=C ls -R
>> .:
>> build-time  configs  scripts  toolchain-amd64
>>
>> ./build-time:
>> ls-alt_building-4-4-25-under-4-8-2.txt
>> ls-alt_building-4-8-2-under-4-9-0-rc1.txt
>>
>> ./configs:
>> WHATS-IN-DILEKS-LINUX-KERNEL.txt  config-4.4.25-1-iniza-small
>> config-4.8.2-1-iniza-small  config-4.9.0-rc1-1-iniza-small
>>
>> ./scripts:
>> build_linux-upstream.sh
>>
>> ./toolchain-amd64:
>> HOST-AND-BUILD-TOOLCHAIN.txt
>
>
>
> Thanks,
> Ming Lei