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

[Nivedita Singhvi <niv@xxxxxxxxxx>]

Diwaker Gupta wrote:

> Hi folks,
>
> I was to post this over the weekend, but didn't get around to it, and
> look in the meanwhile Xen 3.0.0 was released! Good work all around,
> but I got some performance problems to report :)
>
> 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?
Diwaker,

Can you run oprofile and obtain any kind of breakdown
on that, if possible? Also, are you dedicating individual
CPUs to dom0 and guest? (Avoiding much of the context
switching on I/O). What are your memory allocations? How much
of a bump do you get if you increase memory?

thanks,
Nivedita



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