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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Sat, 16 Nov 2019 16:17:49 +0900
Message-ID: <CAK7LNATVHbMHqjboACJF8BbKianRfjiGhHTXjtQuJVmv2HFPUA@mail.gmail.com>
Subject: Re: Recent slowdown in single object builds
To:     Jens Axboe <axboe@kernel.dk>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Sat, Nov 16, 2019 at 8:10 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> Hi,
>
> I've noticed that current -git is a lot slower at doing single object
> builds than earlier kernels. Here's an example, building the exact same
> file on 5.2 and -git:
>
> $ time make fs/io_uring.o
> real    0m5.953s
> user    0m5.402s
> sys     0m0.649s
>
> vs 5.2 based (with all the backports, identical file):
>
> $ time make fs/io_uring.o
> real    0m3.218s
> user    0m2.968s
> sys     0m0.520s
>
> Any idea what's going on here? It's almost twice as slow, which is
> problematic...


This is necessary cost
to do single builds
(394053f4a4b3e3eeeaa67b67fc886a9a75bd9e4d)
but, it is much better in linux-next.


-- 
Best Regards
Masahiro Yamada