Re: [Qemu-devel] Re: [RFC] Disk integrity in QEMU

[Laurent Vivier]

Le jeudi 16 octobre 2008 à 08:43 -0500, Anthony Liguori a écrit :
> Laurent Vivier wrote:
> > Hi,
> >
> > I've made a benchmark using a database:
> > mysql and sysbench in OLTP mode.
> >
> > cache=off seems to be the best choice in this case...
> >   
> 
> It would be interesting for you to run the same workload under KVM.

It is done under KVM... and I've just double checked these values.

> > mysql database
> > http://sysbench.sourceforge.net
> >
> > sysbench --test=oltp
> >
> > 200,000 requests on 2,000,000 rows table.
> >
> >                  | total time | per-request stat (ms) |
> >                  |  (seconds) |  min  |  avg  |  max  |
> > -----------------+------------+-------+-------+-------+
> > baremetal        |   208.6237 |   2.5 |  16.7 | 942.6 |
> > -----------------+------------+-------+-------+-------+
> > cache=on         |   642.2962 |   2.5 |  51.4 | 326.9 |
> > -----------------+------------+-------+-------+-------+
> > cache=on,O_DSYNC |   646.6570 |   2.7 |  51.7 | 347.0 |
> > -----------------+------------+-------+-------+-------+
> > cache=off        |   635.4424 |   2.9 |  50.8 | 399.5 |
> > -----------------+------------+-------+-------+-------+
> >   
> 
> Because you're talking about 1/3% of native performance.  This means 
> that you may be dominated by things like CPU overhead verses actual IO 
> throughput.

Yes, but as it is KVM I have no explanation...

I've another interesting result with scsi-generic :

-----------------+------------+-------+-------+-------+
scsi-generic     |   634.1303 |   2.8 |  50.7 | 308.6 |
-----------------+------------+-------+-------+-------+

Regards,
Laurent
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