Re: Why not build kernel with -O3

From: Austin S Hemmelgarn
Date: Wed Apr 08 2015 - 08:49:21 EST

On 2015-04-08 08:19, Richard Weinberger wrote:
On Wed, Apr 8, 2015 at 3:00 AM, Pengfei Yuan <0xcoolypf@xxxxxxxxx> wrote:
Could you please provide some examples that I can investigate?

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?

My guess would be that much of the speed up is actually related to context switch handling and the scheduling/statistics related code.

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature