From: Mike Fedyk <mfedyk@matchmail.com>
To: Oleg Drokin <green@namesys.com>
Cc: Jeff Breidenbach <jbreiden@parc.com>,
Hans Reiser <reiser@namesys.com>,
reiserfs-list@namesys.com
Subject: Prereading block device doesn't help filesystems
Date: Tue, 3 Jun 2003 10:49:35 -0700 [thread overview]
Message-ID: <20030603174935.GA4044@matchmail.com> (raw)
In-Reply-To: <20030603053336.GC8667@namesys.com>
On Tue, Jun 03, 2003 at 09:33:36AM +0400, Oleg Drokin wrote:
> (e.g. dd if=/dev/hdb1 /dev/zero bs=1024k count=500 (replace 500 with the half of your RAM
> in megabytes) and you have large enough RAM, there is a chance that this will cache
> enough data to keep stuff moving more quickly.
That won't work either.
Basically you're copying the data into buffer cache, and the page cache
won't be able to pick it up, so you're going to read from the disk twice.
Even with Andrea's buffercache in pagecache from 2.4.10 it doesn't do the
aliasing IIRC. And there were some long threads where Linus said he
wouldn't accept patches to do the aliasing either.
Don't know if he has changed his mind in 2.5 though...
next prev parent reply other threads:[~2003-06-03 17:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-28 20:07 disk or reiserfs problem? Jeff Breidenbach
2003-05-29 5:45 ` Oleg Drokin
2003-06-02 18:36 ` Hans Reiser
2003-06-02 20:00 ` Jeff Breidenbach
2003-06-03 5:33 ` Oleg Drokin
2003-06-03 17:49 ` Mike Fedyk [this message]
2003-06-03 18:19 ` Prereading block device doesn't help filesystems Chris Mason
2003-06-05 13:20 ` disk or reiserfs problem? Hans Reiser
2003-06-05 13:38 ` Nikita Danilov
2003-06-03 5:23 ` Oleg Drokin
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