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Re: [Xen-devel] 2.4.29-xenU VBD performance (problem)

On Wed, Feb 16, 2005 at 11:14:50PM -0000, Ian Pratt wrote:
> > Both the dom0 and domU were using 128 MB of RAM. I tested with:
> > "dd if=/dev/zero of=/dev/foo bs=1024k count=2048". That makes 
> > 2 GB of data to
> > write, so that will definitely not fit in the RAM / buffers. I ran the
> > "test" three times on each kernel to be sure about the result.
> > The CPU in the test-box was 3 GHz P4 with 1 MB of l2-cache. 
> > The box (both
> > the dom0 and domU) were idle besides running the test.
> Have you tried enabling hyperthreading and running the dom0 and domU's on 
> different threads?

I enabled hyperthreading and ran dom0 with cpu0 and domU with cpu1.

dom0 performance remained the same as previously (93 MB/sec).

2.6.10-xenU performance increased from 58 MB/sec -> 69 MB/sec.
2.4.29-xenU performance remained the same at 23 MB/sec.

It seems that enabling hyperthreading and running domains with different
(virtual) cpu:s increase performance.

Hyperthreading enabled, but running domU with same (virtual) cpu as dom0
caused the performance to be the same as with hyperthreading disabled.

> We haven't done any testing with software raid 5 systems. It's possible the 
> extra CPU burnt by dom0 is causing bad scheduling interactions.

It might be.. anyway, 2.4-domU performance is really bad..

-- Pasi Kärkkäinen
                                .     .
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