From: Adrian Bunk <bunk@stusta.de>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Benjamin LaHaise <bcrl@kvack.org>,
Oleg Verych <olecom@flower.upol.cz>, rae l <crquan@gmail.com>,
linux-kernel@vger.kernel.org
Subject: -Os versus -O2
Date: Mon, 25 Jun 2007 02:41:06 +0200 [thread overview]
Message-ID: <20070625004106.GA1094@stusta.de> (raw)
In-Reply-To: <1182731022.6819.10.camel@laptopd505.fenrus.org>
On Sun, Jun 24, 2007 at 05:23:42PM -0700, Arjan van de Ven wrote:
> On Sun, 2007-06-24 at 20:12 -0400, Benjamin LaHaise wrote:
> > On Sun, Jun 24, 2007 at 05:09:16PM -0700, Arjan van de Ven wrote:
> > > if you care about the last cycle, don't specify -Os but -O2.
> > > simple as that... you get what you tell the compiler you want.
> >
> > Certain distros are shipping kernels compiled with -Os. And it's more
> > than just a couple of cycles.
>
> so those distros pick space over some cycles. Who are you to then
> override that choice ? ;-)
>
> seriously, why are we even talking about overriding a choice the user
> (or distro vendor as user) made here?
There is a real issue in the fact that compiling with -Os is available
through a kconfig option and AFAIR used by some distributions.
I doubt distros enable CONFIG_CC_OPTIMIZE_FOR_SIZE due to size
considerations, but due to speed considerations.
I wouldn't care if CONFIG_CC_OPTIMIZE_FOR_SIZE was hidden behind
CONFIG_EMBEDDED, but as long as it's available as a general purpose
option we have to consider it's performance.
The interesting questions are:
Does -Os still sometimes generate faster code with gcc 4.2?
If yes, why?
cu
Adrian
--
"Is there not promise of rain?" Ling Tan asked suddenly out
of the darkness. There had been need of rain for many days.
"Only a promise," Lao Er said.
Pearl S. Buck - Dragon Seed
next prev parent reply other threads:[~2007-06-25 0:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-23 5:15 [PATCH] trivial: the memset operation on a automatic array variable should be optimized out by data initialization Denis Cheng
2007-06-23 7:59 ` Oleg Verych
2007-06-23 13:13 ` Adrian Bunk
2007-06-23 13:41 ` Oleg Verych
2007-06-23 13:57 ` Adrian Bunk
2007-06-23 15:21 ` Segher Boessenkool
2007-06-24 12:58 ` rae l
2007-06-24 22:25 ` Oleg Verych
2007-06-24 22:15 ` Arjan van de Ven
2007-06-24 23:23 ` Benjamin LaHaise
2007-06-25 0:09 ` Arjan van de Ven
2007-06-25 0:12 ` Benjamin LaHaise
2007-06-25 0:23 ` Arjan van de Ven
2007-06-25 0:41 ` Adrian Bunk [this message]
2007-06-25 0:58 ` -Os versus -O2 Arjan van de Ven
2007-06-25 1:08 ` david
2007-06-25 1:17 ` Arjan van de Ven
2007-06-25 1:33 ` david
2007-06-25 1:41 ` Rene Herman
2007-06-25 5:04 ` Willy Tarreau
2007-06-25 7:08 ` Segher Boessenkool
2007-06-25 7:15 ` david
2007-06-25 7:41 ` Segher Boessenkool
2007-06-25 8:19 ` Willy Tarreau
2007-06-25 8:41 ` Segher Boessenkool
2007-06-25 7:03 ` Segher Boessenkool
2007-06-25 7:13 ` david
2007-06-25 7:35 ` Segher Boessenkool
2007-06-25 1:33 ` Adrian Bunk
2007-06-25 1:23 ` Rene Herman
2007-06-25 1:31 ` Rene Herman
2007-06-25 1:34 ` Jeff Garzik
2007-06-25 1:46 ` Adrian Bunk
2007-06-25 2:19 ` david
2007-06-24 23:33 ` memset() with zeroes (Re: [PATCH] trivial: the memset operation on a automatic array variable should be optimized out by data initialization) Oleg Verych
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