linux-kernel - Re: [PATCH 07/13] block: avoid indirect calls to enter cfq io scheduler

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Message-ID: <807b3a220905260202u11a9a9f8wd1874fce82d6b313@mail.gmail.com>
Date:	Tue, 26 May 2009 14:32:27 +0530
From:	Nikanth K <nikanth@...il.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
	akpm@...ux-foundation.org, jack@...e.cz,
	yanmin_zhang@...ux.intel.com,
	Nikanth Karthikesan <knikanth@...e.de>
Subject: Re: [PATCH 07/13] block: avoid indirect calls to enter cfq io 
	scheduler

On Mon, May 25, 2009 at 1:00 PM, Jens Axboe <jens.axboe@...cle.com> wrote:
>
> They can be expensive, since CPUs generally do not branch predict
> well for them.
>

Cant gcc take care of this? Comparing a pointer and then calling the
function directly without using the pointer! Wont this increase the
text size of the kernel and possibly degrade performance? Do you have
any measurement of the improvement? Is this kind of optimization being
used elsewhere?

Thanks
Nikanth
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