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
next prev 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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130127124942.GB3933@gmail.com \
--to=mingo@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=arjan@linux.intel.com \
--cc=bp@alien8.de \
--cc=hpa@zytor.com \
--cc=jbeulich@suse.com \
--cc=ling.ml@alipay.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=rostedt@goodmis.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).