linux-kernel - Re: [PATCH 04/20] Convert gfp_zone() to use a table of precalculated value

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Message-ID: <alpine.DEB.1.10.0902231130280.3333@qirst.com>
Date:	Mon, 23 Feb 2009 11:33:00 -0500 (EST)
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Mel Gorman <mel@....ul.ie>
cc:	Linux Memory Management List <linux-mm@...ck.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Rik van Riel <riel@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>
Subject: Re: [PATCH 04/20] Convert gfp_zone() to use a table of precalculated
 value

On Mon, 23 Feb 2009, Mel Gorman wrote:

> I was concerned with mispredictions here rather than the actual assembly
> and gfp_zone is inlined so it's lot of branches introduced in a lot of paths.

The amount of speculation that can be done by the processor pretty
limited to a few instructions. So the impact of a misprediction also
should be minimal. The decoder is likely to have sucked in the following
code anyways.

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