On 08/17/2010 12:51 AM, Alex Rixhardson wrote:
I tried with 'notsc divider=10' (since it's 64 bit guest), but the
results are the still same :-(. The guest is idle at the time of
testing. It has 2 CPU and 1024 MB RAM available.

Hmm, are you using e1000 or virtio for the 4.5 guest?
e1000 should be slow since it's less suitable for virtualization (3 mmio/packet)



On Mon, Aug 16, 2010 at 11:35 PM, Dor Laor<dl...@redhat.com>  wrote:
On 08/17/2010 12:22 AM, Alex Rixhardson wrote:

Thanks for the suggestion.

I tried with the netperf. I ran netserver on host and netperf on RHEL
5.5 and RHEL 4.5 guests. This are the results of 60 seconds long
tests:

RHEL 4.5 guest:
Throughput (10^6bits/sec) = 145.80

At least it bought you another 5Mb/s over iperf ...

It might be time related, 5.5 has kvmclock but rhel4 does not.
If it's 64 bit guest add this to the 4.5 guest cmdline  'notsc divider=10'.
If it's 32 use 'clock=pmtmr divider=10'.
The divider is probably new and is in rhel4.8 only, it's ok w/o it too.

What's the host load for the 4.5 guest?


RHEL 5.5 guest:
Throughput (10^6bits/sec) = 3760.24

The results are really bad on RHEL 4.5 guest. What could be wrong?

Regards,
Alex

On Mon, Aug 16, 2010 at 9:49 PM, Dor Laor<dl...@redhat.com>    wrote:

On 08/16/2010 10:00 PM, Alex Rixhardson wrote:

Hi guys,

I have the following configuration:

1. host is RHEL 5.5, 64bit with KVM (version that comes out of the box
with RHEL 5.5)
2. two guests:
2a: RHEL 5.5, 32bit,
2b: RHEL 4.5, 64bit

If I run iperf between host RHEL 5.5 and guest RHEL 5.5 inside the
virtual network subnet I get great results (>      4Gbit/sec). But if I
run
iperf between guest RHEL 4.5 and either of the two RHELs 5.5 I get bad
network performance (around 140Mbit/sec).

Please try netperf, iperf known to be buggy and might consume cpu w/o
real
justification


The configuration was made thru virtual-manager utility, nothing
special. I just added virtual network device to both guests.

Could you guys give me some tips on what should I check?

Regards,
Alex
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