From: Ted Ts'o <tytso@mit.edu>
To: "Alexander V. Lukyanov" <lav@netis.ru>
Cc: linux-ext4@vger.kernel.org, Andreas Dilger <adilger@sun.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ext4: allow inode_readahead_blks=0 (linux-2.6.37)
Date: Mon, 21 Feb 2011 21:32:11 -0500 [thread overview]
Message-ID: <20110222023211.GF2924@thunk.org> (raw)
In-Reply-To: <20110208063925.GA13619@lw.yar.ru>
On Tue, Feb 08, 2011 at 09:39:25AM +0300, Alexander V. Lukyanov wrote:
> Hello!
>
> I cannot disable inode-read-ahead feature of ext4 (on 2.6.37):
>
> # echo 0 > /sys/fs/ext4/sda2/inode_readahead_blks
> bash: echo: write error: Invalid argument
>
> On a server with lots of small files and random access this read-ahead makes
> performance worse, and I'd like to disable it. I work around this problem
> by using value of 1, but it still reads an extra block.
So I'm curious --- have you actually benchmarked a performance
decrease? What sort of hardware are you using?
The readahead should be changing a 4k read to a 8k read with a value
of 1, which shouldn't take a much of a difference to a HDD.
I can apply this patch, but is it really making a difference for you?
- Ted
next prev parent reply other threads:[~2011-02-22 2:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-08 6:39 [PATCH] ext4: allow inode_readahead_blks=0 (linux-2.6.37) Alexander V. Lukyanov
2011-02-22 2:32 ` Ted Ts'o [this message]
2011-02-24 8:18 ` Alexander V. Lukyanov
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