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From: Ingo Molnar <mingo@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Jan Beulich <jbeulich@suse.com>,
	ling.ml@alipay.com, Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/asm] x86/defconfig: Turn on CONFIG_CC_OPTIMIZE_FOR_SIZE= y in the 64-bit defconfig
Date: Sun, 27 Jan 2013 13:49:42 +0100	[thread overview]
Message-ID: <20130127124942.GB3933@gmail.com> (raw)
In-Reply-To: <1359234167.17639.3.camel@gandalf.local.home>


* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Sat, 2013-01-26 at 11:43 -0800, Linus Torvalds wrote:
> 
> > The problem, of course, is that most -O2 code generation is done
> > assuming hot loops that don't show much if any I$ issues. And the -Os
> > thing is done *purely* for size, not taking any performance into
> > account at all. There's no balanced middle ground, which is what _we_
> > would want.
> 
> Gcc needs to implement a -Olinus

What we really want is a sane default for 'library code' 
optimization:

 - cache-cold optimizations for run-through-once non-looping 
   code (-Os)

 - good loop optimizations for anything that arguably loops (-O2)

 - plus common-sense fixes to -Os like not throwing away 
   explicit branch hints we go to great pains to insert.

Possibly some time this decade.

Thanks,

	Ingo

  parent reply	other threads:[~2013-01-27 12:49 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-25 14:11 [PATCH] [x86]: Compiler Option Os is better on latest x86 ling.ma.program
2013-01-26 12:25 ` [tip:x86/asm] x86/defconfig: Turn on CONFIG_CC_OPTIMIZE_FOR_SIZE= y in the 64-bit defconfig tip-bot for Ma Ling
2013-01-26 12:52   ` Borislav Petkov
2013-01-26 15:18     ` H. Peter Anvin
2013-01-26 15:42       ` Borislav Petkov
2013-01-26 19:43       ` Linus Torvalds
2013-01-26 21:02         ` Steven Rostedt
2013-01-26 21:04           ` H. Peter Anvin
2013-01-27 12:49           ` Ingo Molnar [this message]
2013-01-26 21:08         ` H. Peter Anvin
2013-01-28 17:15 ` [PATCH] [x86]: Compiler Option Os is better on latest x86 Valdis.Kletnieks
2013-01-29  8:12   ` Ingo Molnar

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