linux-kernel - Re: Why not build kernel with -O3

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Message-ID: <CAFLxGvzZuddx=GA5HTZzJb_=_6U9RRSDS-iRoer7u8T8p8VrmA@mail.gmail.com>
Date:	Wed, 8 Apr 2015 14:19:02 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Pengfei Yuan <0xcoolypf@...il.com>
Cc:	Austin S Hemmelgarn <ahferroin7@...il.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Why not build kernel with -O3

On Wed, Apr 8, 2015 at 3:00 AM, Pengfei Yuan <0xcoolypf@...il.com> wrote:
> Could you please provide some examples that I can investigate?
> Thanks!

It would be awesome if you could find out which gcc optimizations
cause the speed up.
"gcc -c -Q -O3 --help=optimizers" will help you.

Please also double check your results.
You need do to multiple runs, etc...
Especially the redis speed up looks odd. Does redis really spend that much time
in the kernel?

-- 
Thanks,
//richard
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