From: Valdis.Kletnieks@vt.edu
To: ling.ma.program@gmail.com
Cc: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com,
linux-kernel@vger.kernel.org, Ma Ling <ling.ml@alipay.com>
Subject: Re: [PATCH] [x86]: Compiler Option Os is better on latest x86
Date: Mon, 28 Jan 2013 12:15:57 -0500 [thread overview]
Message-ID: <26437.1359393357@turing-police.cc.vt.edu> (raw)
In-Reply-To: Your message of "Fri, 25 Jan 2013 09:11:01 -0500." <1359123061-6139-1-git-send-email-ling.ma@alipay.com>
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On Fri, 25 Jan 2013 09:11:01 -0500, ling.ma.program@gmail.com said:
> Based on above reasons, we compiled linux kernel 3.6.9 with O2 and Os
> respectively. The results show Os improve performance netperf 4.8%,
> 2.7% for volano as below
Am I allowed to NAK this? What the numbers given so far *actually*
show is 4.8% more instructions executed, *not* 4.8% better performance.
I'm having a *very* hard time convincing myself that what we're seeing isn't
simply the expected behavior of loops *not* being unrolled and similar
non-optimizations done by -Os, so more instructions get executed to do the same
amount of work.
Rather than "run for 10 seconds and count instructions", can we
"run for 50,000 syscalls and count clock time" or similar that shows
an *actual* improvement?
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next prev parent reply other threads:[~2013-01-28 17:16 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-25 14:11 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
2013-01-26 21:08 ` H. Peter Anvin
2013-01-28 17:15 ` Valdis.Kletnieks [this message]
2013-01-29 8:12 ` [PATCH] [x86]: Compiler Option Os is better on latest x86 Ingo Molnar
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