Message-ID: <464E2098.8020900@cfl.rr.com>
Date: Fri, 18 May 2007 17:54:32 -0400
From: Phillip Susi <psusi@cfl.rr.com>
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To: Andrew Morton <akpm@linux-foundation.org>
CC: Alex Volkov <avcp-lkmail@usa.net>, "'Jeff Garzik'" <jeff@garzik.org>,
       "'Linux Kernel Mailing List'" <linux-kernel@vger.kernel.org>
Subject: Re: aio is unlikely
References: <20070509151831.f5956b66.akpm@linux-foundation.org> <058f01c7998e$1406e370$650df7cd@MUMBA> <20070518140624.1a4db517.akpm@linux-foundation.org>
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Andrew Morton wrote:
> Yes, if you agree with Jeff's original point.
> 
> But I don't, actually.  Sure, on some machines+workloads, AIO is more
> common than sync IO.  But I expect that when we sum across all the
> machines+workloads in the world, sync IO is more common and is hence the
> case we should optimise for.
> 
> That's assuming that the unlikely() actually does something.

But as Jeff said, that's not what unlikely is for.  It should only be 
used when it is unlikely for everybody, all the time, because when it is 
right, it helps rather little, but when it is wrong, it hurts a lot.

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