Re: OSDL aio-stress results on latest kernels show buffered randomread issue

From: Judith Lebzelter
Date: Thu Sep 30 2004 - 17:03:55 EST


On Wed, 29 Sep 2004, William Lee Irwin III wrote:

> On Wed, Sep 29, 2004 at 04:29:08PM -0700, Judith Lebzelter wrote:
> > There seems to be an issue with the reads. Usually, reads
> > should be at least as fast as writes of the same type.
> > Also, there seems to be a substantial drop-off in the performance
> > of AIO buffered-random writes in the mm kernels. (14% on 2CPU,
> > 40% on 4CPU)
>
> Okay, is it cpu time or idle/iowait? If it's cpu time, where do
> profiles show it appears?

Th CPU is not that busy:

2.6.9-rc2-mm4 Results and iostat outputs:
http://khack.osdl.org/stp/297714/
http://khack.osdl.org/stp/297714/results/bufferrand/iostat.txt

2.6.9-rc2 Results and iostat outputs:
http://khack.osdl.org/stp/297545/
http://khack.osdl.org/stp/297545/results/bufferrand/iostat.txt


The iostat has the write stats followed by the reads, taken every 15
seconds.

>
>
> -- wli
>

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