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From: Jeff Garzik <jeff@garzik.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Phillip Susi <psusi@cfl.rr.com>,
	Alex Volkov <avcp-lkmail@usa.net>,
	"'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>
Subject: Re: aio is unlikely
Date: Fri, 18 May 2007 23:50:33 -0400	[thread overview]
Message-ID: <464E7409.6020505@garzik.org> (raw)
In-Reply-To: <464E7254.60406@yahoo.com.au>

Nick Piggin wrote:
> Aside from using branch constructs or hints that help the predictor
> guess the right way... I think gcc will move unlikely paths right past
> the end of the "likely" fastpath, so it can increase code size and be
> somewhat suboptimal in terms of icache usage.

Thanks for the reminder.  GCC definitely does code movement.

ISTR the code movement might even be "extreme", once the unit-at-a-time 
support arrived, placing "cold" code at the end of the compiled module.

	Jeff



  reply	other threads:[~2007-05-19  3:50 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <200705092101.l49L1CF1023363@hera.kernel.org>
2007-05-09 22:06 ` aio is unlikely Jeff Garzik
2007-05-09 22:18   ` Andrew Morton
2007-05-09 22:37     ` Jeff Garzik
2007-05-18 20:49     ` Alex Volkov
2007-05-18 21:06       ` Andrew Morton
2007-05-18 21:11         ` Jeff Garzik
2007-05-18 21:54         ` Phillip Susi
2007-05-18 22:12           ` Andrew Morton
2007-05-18 22:37             ` Jeff Garzik
2007-05-19  3:43               ` Nick Piggin
2007-05-19  3:50                 ` Jeff Garzik [this message]
2007-05-18 21:30       ` Bernd Eckenfels

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