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Message-ID: <Pine.LNX.4.64.0705090918390.12857@p34.internal.lan>
Date: Wed, 9 May 2007 09:22:08 -0400 (EDT)
From: Justin Piszcz <jpiszcz@...idpixels.com>
To: axboe@...e.de
cc: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
Alan Piszcz <ap@...arrain.com>
Subject: Chaining sg lists for big I/O commands: Question
http://kerneltrap.org/node/8176
I am a mdadm/disk/hard drive fanatic, I was curious:
> On i386, we can at most fit 256 scatterlist elements into a page,
> and on x86-64 we are stuck with 128. So that puts us somewhere
> between 512kb and 1024kb for a single IO.
How come 32bit is 256 and 64 is only 128?
I am sure it is something very fundamental/simple but I was curious, I
would think x86_64 would fit/support more scatterlists in a page.
Also, when this patch is implemented for x86_64 and if merged into
mainline, what does this mean for performance?
I have an mdadm raid5 of 10 raptors and get 434MB/s write and 622MB/s
read, would I see an increase in performance with this patch?
Justin.
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