From: age <ahuisman@cistron.nl>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org, nuno.silva@vgertech.com
Subject: Re: READAHEAD
Date: Fri, 31 Oct 2003 13:20:07 +0100 [thread overview]
Message-ID: <3FA25377.3050207@cistron.nl> (raw)
In-Reply-To: <20031030134407.0c97c86e.akpm@osdl.org>
Andrew Morton wrote:
> age <ahuisman@cistron.nl> wrote:
>
>>I have a problem which i don`t understand and i hope that you
>> will and can help me. The problem is that i experience strange disk
>> read performance. I have to set hdparm -m16 -u1 -c1 -d1 -a4096 /dev/hde
>> to get timing buffered disk reads of 56 MB/SEC.
>> When i disable readahead i get 17 MB/SEC
>> When i enable readahead with -a8 i get 17 MB/SEC
>> When i enable readahead with -a16 i get 24,5 MB/SEC
>> When i enable readahead with -a32 i get 30,5 MB/SEC
>> When i enable readahead with -a64 i get 35 MB/SEC
>> When i enable readahead with -a128 i get 39 MB/SEC
>> When i enable readahead with -a256 i get 39 MB/SEC
>> When i enable readahead with -a512 i get 41 MB/SEC
>> When i enable readahead with -a1024 i get 50 MB/SEC
>> When i enable readahead with -a2048 i get 50 MB/SEC
>> When i enable readahead with -a4096 i get 56 MB/SEC
>> With -a8192,-a16384 and -a32768 i get also 56MB/SEC
>>
>> Before, i never had to set readahead so high
>> Please could you tell me, what is going on here ?
>
>
> Lots of people have been reporting this. It's rather weird.
>
> Is the same effect observable when reading a large file, or is it only
> observable via `hdparm -t'?
>
Hi Andrew,
Here are some tests with bonnie++.
The used command is : bonnie++ -d /home/test -s 1024 -n 10 -u root
TCQ and write cache enabled.
The first test with hdparm -a0 -c1 -m16 -u1 -d1 /dev/hde :
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
wuuk 1G 3610 98 56878 85 10010 35 3129 90 17355 55 181.2 2
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
10 11117 95 +++++ +++ 18414 98 11888 99 +++++ +++ 19189 98
The second test with hdparm -a16 -c1 -m16 -u1 -d1 /dev/hde :
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
wuuk 1G 3611 98 56404 85 12104 36 3260 92 27741 54 193.3 1
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
10 11571 99 +++++ +++ 18477 99 11901 99 +++++ +++ 19250 99
The third test with hdparm -a256 -c1 -m16 -u1 -d1 /dev/hde :
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
wuuk 1G 3614 98 57510 85 15597 28 3621 95 43004 45 188.5 1
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
10 11622 99 +++++ +++ 18439 99 11905 99 +++++ +++ 19378 99
The fourth test with hdparm -a4096 -c1 -m16 -u1 -d1 /dev/hde :
Version 1.03 ------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP
wuuk 1G 3610 98 57770 85 18518 32 3636 96 42748 39 186.9 1
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP
10 11653 98 +++++ +++ 18608 99 11908 99 +++++ +++ 19503 99
If you need more information, please tell me.
groetjes,(greetings)
Age Huisman.
next prev parent reply other threads:[~2003-10-31 9:18 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 ` age [this message]
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 ` READAHEAD Derek Foreman
-- 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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