linux-kernel - Re: SATA Harddisk speed drop of 100 MB/s

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Date:	Sat, 23 Jun 2007 08:26:01 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	linux-kernel@...r.kernel.org
Subject: Re: SATA Harddisk speed drop of 100 MB/s

Carlo Wood wrote:
> Just one kernel version? The problem here is in every
> kernel revision after 551c012d7eea3dc5ec063c7ff9c718d39e77634f
>
> 2.6.20-rc2,rc3,rc4,rc5,rc6,rc7 ... 2.6.20 ... 2.6.21 ... 2.6.22-rc5
>
> noop:
>  Timing buffered disk reads:  254 MB in  3.00 seconds =  84.66 MB/sec
>
> anticipatory:
>  Timing buffered disk reads:  252 MB in  3.02 seconds =  83.43 MB/sec
>
> deadline:
>  Timing buffered disk reads:  258 MB in  3.02 seconds =  85.41 MB/sec
>
> cfq:
>  Timing buffered disk reads:  194 MB in  3.03 seconds =  64.06 MB/sec
>
> The normal value is cfq. So, all other schedulars are somewhat faster,
> but still far from the correct 165 MB/s.

You may want to play with /sys/block/*/queue/max_sectors_kb and 
read_ahead_kb.  On my system, setting them to 192 gives best performance, 
but cfq is always slower.


Thanks!

--
Al

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