Re: [Xen-users] Xen hard-disk performance regression?

[Fabiano Francesconi <fabiano.francesconi@xxxxxxxxx>]

On Mon, Apr 12, 2010 at 01:41:19AM +0200, Olivier B. wrote:
> On 12/04/2010 01:29, Fabiano Francesconi wrote:
> > I've tried with a (almost) vanilla kernel (only gentoo patchsets).
> >
> > I have the same issue so, I guess, it's a kernel misconfiguration /
> > kernel regression but it must be something wrong upstream too.
> >
> > Since I've been sharing with you my whole anamnesi, any of you has any
> > clue?
> >    
> 
> Can you try some more synthetics tests, with "dd" ?|
> latency on writes : dd oflag=dsync if=/dev/zero of=TESTFILE bs=4k 
> count=10000
> write speed :|| dd conv=fdatasync if=/dev/zero of=TESTFILE bs=4k 
> count=128000
> read speed : ||dd if=/dev/sda of=/dev/null bs=4k count=128000||| (this 
> one will be greatly affected by cache)
> 
> And can you try with differents FS, ext3 and ext4 for example ?
> 
> Olivier

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I've ran the test you pointed me out. The results are interesting
althought I haven't found an explanation for such a behaviour.

The dsync transfer ration is more than a minute slower on .32 kernel.
The same for fdatasync.

This for what concerns the root hard-disk (that's *not* the one I've
been talking since now).

The storage hard-drive, instead, shows that dsync transfer is _very_
faster on .32, but fdatasync isn't.

These results are very strange.

You'll find both log file attached here. I made them in a way you can
easily (vim)diff those.

-- 
Fabiano Francesconi [GPG key: 0x81E53461]

Attachment: dd.2.6.29.log
Description: Text document

Attachment: dd.2.6.32.log
Description: Text document

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