RE: [Xen-devel] n/w performance degradation

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> I'm running Changeset 
> 00c349d5b40d269da4fec9510f1dd7c6bb3b3327. This is a dual CPU 
> machine but I'm currently running with noht, nosmp. All tests 
> are done using iperf -- both endpoints are sitting on the 
> same switch on our cluster. The machines have Broadcom BCM5704 NICs.
> 
> N/W performance from dom0 seems fine (though I used to get 
> 930+ until a few days back):
> 
> [  6]  0.0-20.0 sec  1.95 GBytes    835 Mbits/sec
> 
> However, from a VM, the throughput is really bad:
> 
> [  5]  0.0-20.0 sec  1.05 GBytes    450 Mbits/sec
> 
> The above numbers are using the BVT scheduler. With the SEDF 
> scheduler, the numbers are even worse (a VM can't get more 
> than 300Mbps in my tests). I can post concrete figures if 
> people are interested. I'm _not_ running pipelined netback.
> 
> Is anyone else observing such performance problems?

We haven't really done much tuing for the single CPU case recently as
the vast majority of platforms that Xen is used on are either
hyperthreaded, dual core or SMP.

The main focus of the 3.0.0 release has been corectness rather than
performance tuning. We plan to do some tweaking over the coming weeks to
address this. We used to get 900Mb/s with a single CPU core, and there's
absoloutely no reason why we shouldn't do so again -- in fact, we should
do better in terms of CPU usage than 2.0 as as we now have checksum
offload.

Now we have great performance monitoring tools like xen-oprofile,
xenperf, xenmon etc it should be wuite straightforward to optimize
things.  Let's just wait until we've delt with any critical bugs arising
from the release...

Ian



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel