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Re: [Xen-users] performance of pv drivers for windows

To: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-users] performance of pv drivers for windows
From: Sebastian Reitenbach <sebastia@xxxxxxxxxxxxxxxxxxxx>
Date: Wed, 24 Sep 2008 07:43:30 +0200
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On Monday September 22 2008 12:44:31 James Harper wrote:
> > Hello everybody,
> >
> > I tried to measure the performance of the available drivers for
> windows as
> > a HVM guest.
> > I used the gplpv drivers 0.9.11-pre17, the PV drivers from Novell, and
> the
> > drivers from Citrix XenSource with the XenServer 5.
> >
> > The Novell and gplpv drivers were more or less at the same speed, for
> > both, network and disk performance.
> > The disk performance was about 10MB/s reading and writing
> sequentially,
> > and about 1-1.5MB/s for reading and writing randomly.
> > The network speed was about 10-12MB/s, via a GigaBit line.
> XPsp2 has a known problem with LSO (which gplpv drivers support... I
> assume the xensource drivers will too). Please try stopping the firewall
> service (that is _not_ the same as turning off the firewall in network
> settings - you actually have to go into services and stop the service).
I reinstalled the dom0, and also created a fresh windows XP SP2 image.
Disabled the firewall and security center from the services, and ran the tests 
With the firewall disabled, the network performance was much better, however, 
the overall throughput over the time was not constant.
Now I took iperf to measure the performance.
I measured the speeds of the system without any PV drivers, and then the GPLPV 
drivers, and the Novell drivers. The results you can find on the link below.
I used iperf, to measure bandwith, PassMark Performance Test 6.1 to measure 
the disk speed. You will also find the times of the FTP file transfer of the 
large file.

Without any of the PV drivers, I got about 7MB/s random write speed, but with 
PV drivers, it dropped to 1.5 MB/s.
Also with the PV drivers from novell, I got a much better network throughput 

You can see the results here:

> > The Xensource drivers made at least about 30MB/s reading and writing
> > sequentially, but for reading and writing randomly, it was also only
> lousy
> > 1.5MB/s.
> > Via network, over the GigaBit line, with the xensource drivers, the
> speed
> > was about 78 MB/s.
> My testing using iperf has shown that I can reach gigabit speeds on the
> network, so it is possible.
> > The Windows system was a XP SP2.
> > hdparm on the dom0 gives about 60MB/s.
> > The network test was an ftp transfer, just downloading a 500MB file,
> > without writing it to disk, writing to nul. The same in the dom0,
> writing
> > the file to /dev/null gave me 112MB/s.
> Please use iperf to test network speeds. It's a bit more comparable to
> the testing that myself and others have done.
> > So I am wondering, what are the expected speed gains for the gplpv
> > drivers?
> > Is the performance of the drivers bettter with different windows
> versions,
> > e.g. windows server 2003?
> XPsp2 with the firewall service enabled behaves badly when LSO is
> enabled.
> Windows 2003 sp1 has also performed badly in some testing I have done
> (not as badly as XPsp2 - something like 50% worse performance instead of
> 90% worse performance)
> My best results have been under Windows 2003 sp2. SP2 introduced some
> pretty hefty improvements to NDIS which is the windows network driver
> layer.
> The advantages I'd expect to see in performance are due to increased
> throughput and lower CPU usage.
> Also, depending on the test tool you are using, the gplpv disk drivers
> may perform quite poorly. This happens if the tools gives the windows
> kernel buffers that are not aligned to a 512 byte boundary.
> Please run debugview from sysinternals.com while you are running your
> disk performance testing. It will periodically output some stats like:
> XenVbd     stat_interrupts = 2408914
> XenVbd     stat_interrupts_for_me = 314368
> XenVbd     stat_reads = 131507
> XenVbd     stat_writes = 208567
> XenVbd     stat_unaligned_le_4096 = 7
> XenVbd     stat_unaligned_le_8192 = 0
> XenVbd     stat_unaligned_le_16384 = 0
> XenVbd     stat_unaligned_le_32768 = 0
> XenVbd     stat_unaligned_le_65536 = 0
> XenVbd     stat_unaligned_gt_65536 = 0
> XenVbd     stat_no_shadows = 0
> XenVbd     stat_no_grants = 0
> XenVbd     stat_outstanding_requests = 1
> The things I'm interested in are that stat_unaligned_xxx figures. The
> only unaligned requests I see during day to day operations are somewhere
> between 5 and 10 that occur very very early during boot
> (stat_unaligned_le_4096 = 7). However I have seen chkdsk, defrag, and at
> least one testing tool issue requests not aligned on 512 byte
> boundaries. When that happens, the gplpv drivers have to break the
> request into 4096 byte chunks and submit each chunk, one at a time, to
> blkback, which really slows things down.
I had that tool running, but it did not produced any output, I guess I used it 
in a wrong manner ;). 

kind regards

> James

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