From: Derek Foreman <manmower@signalmarketing.com>
To: Andrew Morton <akpm@osdl.org>
Cc: ahuisman@cistron.nl, linux-kernel@vger.kernel.org,
nuno.silva@vgertech.com
Subject: Re: READAHEAD
Date: Sun, 2 Nov 2003 18:15:56 -0600 (CST) [thread overview]
Message-ID: <Pine.LNX.4.58.0311021645260.853@uberdeity> (raw)
In-Reply-To: <20031031012946.3adedc14.akpm@osdl.org>
On Fri, 31 Oct 2003, Andrew Morton wrote:
> Andrew Morton <akpm@osdl.org> wrote:
> >
> > Please, just use time, cat, dd, etc.
> >
> > mount /dev/xxx /mnt/yyy
> > dd if=/dev/zero of=/mnt/yyy/x bs=1M count=1024
> > umount /dev/xxx
> > mount /dev/xxx /mnt/yyy
> > time cat /mnt/yyy/x > /dev/null
>
> And you can do the same against /dev/hdaN if you have a scratch
> partition; that would be interesting.
I don't have a scratch partition, but the effect is quite apparent when
reading from /dev/hd*
I have 384 megs of ram, no swap, and echo 0 > /proc/sys/vm/swappiness
kernel is 2.6.0-test9
hdparm -qa 0 /dev/hde ; dd if=/dev/hde of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 103.038178 seconds (10420815 bytes/sec)
hdparm -qa 128 /dev/hde ; dd if=/dev/hde of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 34.171719 seconds (31421943 bytes/sec)
hdparm -qa 256 /dev/hde ; dd if=/dev/hde of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 34.994348 seconds (30683293 bytes/sec)
hdparm -qa 4096 /dev/hde ; dd if=/dev/hde of=/dev/null bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 22.268371 seconds (48218247 bytes/sec)
(hdparm -t /dev/hde opens /dev/hde and reads it for a few seconds, so
these numbers are much the same as my hdparm -t scores)
I also get similar results from /dev/md0 in another machine (the only
not-ide device I can test on... but it's still a bunch of ide drives).
note...
For people playing with hdparm, hdparm -a 123 -t /dev/drive doesn't set
the readahead before running the test.
next prev parent reply other threads:[~2003-11-03 0:16 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-30 19:23 READAHEAD age
2003-10-30 21:44 ` READAHEAD Andrew Morton
2003-10-31 7:43 ` READAHEAD Nuno Silva
2003-10-31 8:03 ` READAHEAD Andrew Morton
2003-10-31 12:20 ` READAHEAD age
2003-10-31 9:28 ` READAHEAD Andrew Morton
2003-10-31 9:29 ` READAHEAD Andrew Morton
2003-11-01 9:15 ` READAHEAD age
2003-11-03 0:15 ` Derek Foreman [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-09-27 2:38 Readahead Alan Stern
2005-09-27 3:06 ` Readahead Randy.Dunlap
2005-09-27 4:24 ` Readahead Andrew Morton
2005-09-28 18:40 ` Readahead Alan Stern
2003-11-01 17:22 READAHEAD Voluspa
2002-04-16 20:21 readahead Andries.Brouwer
2002-04-16 19:10 readahead Andries.Brouwer
2002-04-16 19:23 ` readahead Andrew Morton
2002-04-16 19:33 ` readahead Jens Axboe
2002-04-16 13:54 readahead Andries.Brouwer
2002-04-16 16:08 ` readahead Steven Cole
2002-04-16 18:25 ` readahead Andrew Morton
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