Mailing List Archive

performance problems
Moin,
I just did a quick comparison regarding speed of xen vs. vmware-workstation
using a FAI installation test (FAI is a debian autoinstaller).

Test setup:
host "burns", athlon xp 2100+, 512MB, via chipset
- provides an nfsroot (on hda)
- second disk is partitioned into hdb1, hdb5, hdb6
- hdb5 and hdb6 are exported to vmware or xenU
- installation pumps 4.1G of software from a local debian mirror to hdb6
(seen as hda6 in xenU/vmware ws) using apt and configures the software
- assigned 192 M of Memory in both cases to the virtual machines
- burns is connected to the local debian mirror using a 1000 mbit NIC and a
switch

xen setup:
- xen 2.0.3, kernel 2.6.10, dma support enabled
- the rest is an out-of-the-box-setup
- support scripts are installed to move /lib/tls out of the way (BTW:
wouldn't LD_ASSUME_KERNEL=2.4.10 have the same effect)
- The installation took 7509 seconds

vmware ws setup:
- locally configured kernel 2.6.9, dma enabled
- bridged networking
- booting from a virtual floppy drive
- accesses hdb{5,6} directly as hda{5,6}
- /lib/tls is left in-place
- The installation took 3068 seconds


Why takes the installation within Xen 7500 sec and in vmware ws 3000 sec ? I
expected Xen to be faster because of the lower overhead...
What could cause this difference ?
Could the scheduling be responsible ?

--
c u
henning


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Re: performance problems [ In reply to ]
well, that's interesting, I wonder if disk I/o performance had a hand in
those results.

I ought to mention that full boot time for Plan 9 in xen is < 10 seconds.

ron



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RE: performance problems [ In reply to ]
I think you're going to have to do a few IO microbenchmarks such as ttcp
and dd to figure out what's going slow on your system -- something is
badly wrong. Are you sure the same hardware drivers are being used in
both cases?

Ian

> -----Original Message-----
> From: xen-devel-admin@lists.sourceforge.net
> [mailto:xen-devel-admin@lists.sourceforge.net] On Behalf Of
> Henning Glawe
> Sent: 19 January 2005 20:36
> To: xen-devel@lists.sourceforge.net
> Subject: [Xen-devel] performance problems
>
> Moin,
> I just did a quick comparison regarding speed of xen vs.
> vmware-workstation
> using a FAI installation test (FAI is a debian autoinstaller).
>
> Test setup:
> host "burns", athlon xp 2100+, 512MB, via chipset
> - provides an nfsroot (on hda)
> - second disk is partitioned into hdb1, hdb5, hdb6
> - hdb5 and hdb6 are exported to vmware or xenU
> - installation pumps 4.1G of software from a local debian
> mirror to hdb6
> (seen as hda6 in xenU/vmware ws) using apt and configures
> the software
> - assigned 192 M of Memory in both cases to the virtual machines
> - burns is connected to the local debian mirror using a 1000
> mbit NIC and a
> switch
>
> xen setup:
> - xen 2.0.3, kernel 2.6.10, dma support enabled
> - the rest is an out-of-the-box-setup
> - support scripts are installed to move /lib/tls out of the way (BTW:
> wouldn't LD_ASSUME_KERNEL=2.4.10 have the same effect)
> - The installation took 7509 seconds
>
> vmware ws setup:
> - locally configured kernel 2.6.9, dma enabled
> - bridged networking
> - booting from a virtual floppy drive
> - accesses hdb{5,6} directly as hda{5,6}
> - /lib/tls is left in-place
> - The installation took 3068 seconds
>
>
> Why takes the installation within Xen 7500 sec and in vmware
> ws 3000 sec ? I
> expected Xen to be faster because of the lower overhead...
> What could cause this difference ?
> Could the scheduling be responsible ?
>
> --
> c u
> henning
>
>
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> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/xen-devel
>


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Re: performance problems [ In reply to ]
On Wednesday 19 January 2005 14:35, Henning Glawe wrote:
> Moin,
> I just did a quick comparison regarding speed of xen vs. vmware-workstation
> using a FAI installation test (FAI is a debian autoinstaller).
>
> Test setup:
> host "burns", athlon xp 2100+, 512MB, via chipset
> - provides an nfsroot (on hda)
> - second disk is partitioned into hdb1, hdb5, hdb6
> - hdb5 and hdb6 are exported to vmware or xenU
> - installation pumps 4.1G of software from a local debian mirror to hdb6
> (seen as hda6 in xenU/vmware ws) using apt and configures the software
> - assigned 192 M of Memory in both cases to the virtual machines
> - burns is connected to the local debian mirror using a 1000 mbit NIC and a
> switch

I really don't know how this installation works, but just in case: Is it
possible "burns" only pulls from the mirror the first time, and on subsequent
installations it is cached? I am wondering if the first test (Xen) it had to
pull data across the network, and on the second test (Vmware) already had the
data cached on burns.

So far I haven't seem much degrade at all in the tests I have run (dbench3,
SDET, kernel compiles). Actually I was quite surprised how well the VBD's IO
performance was so far. The only "significant" degrade I have seen was SDET,
around 12.5% lower than bare metal linux. I have not looked into network
performance yet, but I think that'll be next on my list...

-Andrew Theurer



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Re: performance problems [ In reply to ]
On Wed, Jan 19, 2005 at 09:35:51PM +0100, Henning Glawe wrote:
> Moin,
> I just did a quick comparison regarding speed of xen vs. vmware-workstation
> using a FAI installation test (FAI is a debian autoinstaller).
>
> Test setup:
> host "burns", athlon xp 2100+, 512MB, via chipset
> - provides an nfsroot (on hda)
> - second disk is partitioned into hdb1, hdb5, hdb6
> - hdb5 and hdb6 are exported to vmware or xenU

Don't forget that hdd perfomance decreases as you reach the end of the
disc, and it could have caused a noticeable performance hit.

Regards,
Luciano Rocha

--
1/16


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Re: performance problems [ In reply to ]
On Wed, Jan 19, 2005 at 09:02:02PM -0000, Ian Pratt wrote:
>
> I think you're going to have to do a few IO microbenchmarks such as ttcp
> and dd to figure out what's going slow on your system -- something is
> badly wrong. Are you sure the same hardware drivers are being used in
> both cases?

yup. the only difference was that I didn't touch dumU's kernel config; in
dom0 I already disabled the debugging flags (except magic sysreq), but in
default domU's config they were still enabled.

Overall impression from my newer benchmark experiments:

- Harddisk IO is about 30% faster in XenU than in vmware ws (both accessing
the same raw partition)
- Network IO is at the same level in xenU and vmware, which is about 30%
slower than dom0/native net io (netpipe, 2 machines using 1000Mbit ethernet
connected via a switch, xenU and vmware bridged).

--
c u
henning


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RE: performance problems [ In reply to ]
> yup. the only difference was that I didn't touch dumU's
> kernel config; in
> dom0 I already disabled the debugging flags (except magic
> sysreq), but in
> default domU's config they were still enabled.
>
> Overall impression from my newer benchmark experiments:
>
> - Harddisk IO is about 30% faster in XenU than in vmware ws
> (both accessing
> the same raw partition)
> - Network IO is at the same level in xenU and vmware, which
> is about 30%
> slower than dom0/native net io (netpipe, 2 machines using
> 1000Mbit ethernet
> connected via a switch, xenU and vmware bridged).

It's odd to see such a drop in network performance unless you're on a
machine with a slow CPU. It should be possible to saturate a Gigabit
Ethernet (900Mb/s) with a relatively modern CPU. What are you using?

Ian





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Re: performance problems [ In reply to ]
On Fri, Feb 04, 2005 at 01:08:31PM -0000, Ian Pratt wrote:
>
>
> > yup. the only difference was that I didn't touch dumU's
> > kernel config; in
> > dom0 I already disabled the debugging flags (except magic
> > sysreq), but in
> > default domU's config they were still enabled.
> >
> > Overall impression from my newer benchmark experiments:
> >
> > - Harddisk IO is about 30% faster in XenU than in vmware ws
> > (both accessing
> > the same raw partition)
> > - Network IO is at the same level in xenU and vmware, which
> > is about 30%
> > slower than dom0/native net io (netpipe, 2 machines using
> > 1000Mbit ethernet
> > connected via a switch, xenU and vmware bridged).
>
> It's odd to see such a drop in network performance unless you're on a
> machine with a slow CPU. It should be possible to saturate a Gigabit
> Ethernet (900Mb/s) with a relatively modern CPU. What are you using?

its an athlon XP 2100+, so it isn't _so_ slow...

if someone wants to take a look at the netpipe-tcp results:
http://www.physik.fu-berlin.de/~glaweh/netpipe-xen-benchmark.pdf


--
c u
henning


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Re: performance problems [ In reply to ]
Henning Glawe wrote:

>>It's odd to see such a drop in network performance unless you're on a
>>machine with a slow CPU. It should be possible to saturate a Gigabit
>>Ethernet (900Mb/s) with a relatively modern CPU. What are you using?
>
>
> its an athlon XP 2100+, so it isn't _so_ slow...
>
> if someone wants to take a look at the netpipe-tcp results:
> http://www.physik.fu-berlin.de/~glaweh/netpipe-xen-benchmark.pdf

I took a look at your results. Could you possibly
make available any stats that you collected, and
your system settings? (netstat -s, sysctl -a, ...)

One of the causes for poor performance might be that
the virtual domains are unable to utilize the greater
bandwidth across the virtual bridge using default
socket buffer sizes. Did you bump up the buffer sizes,
queue lengths, etc? A little tuning might help and
give a clearer picture of the real bottlenecks..

thanks,
Nivedita




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