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SubjectRe: SATA Harddisk speed drop of 100 MB/s
Date
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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