Re: [Xen-users] slow dom0 write operations with 2.6.32 pv-ops and Xen4.0.0-rc4

[benco@xxxxxxx]

> You're measuring buffered (cached) performance, so when you limit
> the amount of cache to 2 GB the performance will be slower.
> 
> Try adding "oflag=direct" do your dd commands and test again.


oflag=direct option produce almost the same results on xen and non-xen
systems:

#dd if=/dev/zero of=zerofile.tst bs=1k count=1000000 oflag=direct
1000000+0 records in
1000000+0 records out
1024000000 bytes (1.0 GB) copied, 616.219 s, 1.7 MB/s

what is interesting for me is the fact that with no cpu/memory limit and with
caching the result is approx. 60% slowdown with xen kernel in comparison
with non-xen kernel. Is it normal?

thanks,

roman


<> 
> -- Pasi
> 
> 
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