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Subject: Re: Compiling 2.2.19 with -O3 flag
From: Robert Love <rml@tech9.net>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: samson swanson <intellectcrew@yahoo.com>, linux-kernel@vger.kernel.org
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Date: 24 May 2002 08:19:03 -0700
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On Fri, 2002-05-24 at 07:42, Alan Cox wrote:

> Bench it and see. From my own experience -O3 made the kernel a lot larger
> and reduced overall performance - in part because the kernel already 
> explicitly figures out what it wants inlined.
> 
> Interestingly enough -Os outperformed -O2

Heh, now that is interesting.

Or maybe not - not too long ago I did some tests of the various
optimization options in gcc 2.96 or so and found that -O2 generates
smaller code in most cases than -Os.  -Os also did not perform as good,
but I was just testing a few bits of code - nothing as versatile as the
kernel.

The end result was I recommend -O2 for both performance and size.  Maybe
I should retest against the kernel...

	Robert Love