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SubjectRe: Where is the performance bottleneck?
On Thu, 1 Sep 2005, Nick Piggin wrote:

> Holger Kiehl wrote:
>
>> meminfo.dump:
>>
>> MemTotal: 8124172 kB
>> MemFree: 23564 kB
>> Buffers: 7825944 kB
>> Cached: 19216 kB
>> SwapCached: 0 kB
>> Active: 25708 kB
>> Inactive: 7835548 kB
>> HighTotal: 0 kB
>> HighFree: 0 kB
>> LowTotal: 8124172 kB
>> LowFree: 23564 kB
>> SwapTotal: 15631160 kB
>> SwapFree: 15631160 kB
>> Dirty: 3145604 kB
>
> Hmm OK, dirty memory is pinned pretty much exactly on dirty_ratio
> so maybe I've just led you on a goose chase.
>
> You could
> echo 5 > /proc/sys/vm/dirty_background_ratio
> echo 10 > /proc/sys/vm/dirty_ratio
>
> To further reduce dirty memory in the system, however this is
> a long shot, so please continue your interaction with the
> other people in the thread first.
>
Yes, this does make a difference, here the results of running

dd if=/dev/full of=/dev/sd?1 bs=4M count=4883

on 8 disks at the same time:

34.273340
33.938829
33.598469
32.970575
32.841351
32.723988
31.559880
29.778112

That's 32.710568 MB/s on average per disk with your change and without
it it was 24.958557 MB/s on average per disk.

I will do more tests tomorrow.

Thanks,
Holger

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