linux-ext4 - Re: [PATCH, RFC] ext4: Use preallocation when reading from the inode table

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Message-ID: <20080923101613.58768083@lxorguk.ukuu.org.uk>
Date:	Tue, 23 Sep 2008 10:16:13 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC] ext4: Use preallocation when reading from the
 inode table

On Mon, 22 Sep 2008 20:35:23 -0400
"Theodore Ts'o" <tytso@....edu> wrote:

> 
> With modern hard drives, reading 64k takes roughly the same time as
> reading a 4k block.  So request adjacent inode table blocks to reduce
> the time it takes when iterating over directories (especially when doing
> this in htree sort order) in a cold cache case.  With this patch, the
> time it takes to run "git status" on a kernel tree after flushing the
> caches via "echo 3 > /proc/sys/vm/drop_caches", is reduced by 21%.
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>

Acked-by: Alan Cox <alan@...hat.com>

I'm actually suprised that 16 is the magic tuning number you've used and
a bigger one isn't even more of a win

Alan
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