Re: [Xen-devel] Sending packet at fixed rate really bad performance

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Sep 28, 2009 at 06:28:04PM +0200, Marco Tizzoni wrote:
> On Mon, Sep 28, 2009 at 4:17 PM, Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx> wrote:
> > Lets narrow this down a bit.  You are comparing two different systems
> > with potentially different interfaces. Lets concentrate on one machine
> > first. Is the performance on your Athlon 64 without Xen (meaning you
> > boot without Xen) in the same ball-park figure?
> > I want to make sure we can eliminate the hardware being at fault here.
> 
> I've already done many tests to isolate the problem before writing here.
> I've tried to use a different nic, different LAN, different switch and
> loopback as well, same results.

The problem you described was with two guests. Were those two guests
on two different machines or on the same box?

> Anyway forget aboout Athlon and let compare the same software, on the
> same hardware with linux and xenolinux.
> 
> I've connected two pc running linux via a cross-cable and made some
> tests. The test achieves good results in this case for rate over 10k
> packets/second.
> On xenolinux (credit and sedf behaviour the same) the performance are
> really bad, 250 packets/second (as before).
>

This is with two machines, each connected via cross-cable, running the same
version of Linux, and each running under Xen, correct? The tests executing
under dom0 on both machines?
 
> Also I've just modified my software to not send packets, but simply
> count, so no sendto() is involved. Same low rate.
> 
> May be there's something wrong in my code (not yet finished). Attached
> you can find it if you want have a look or try to reproduce this
> issue.
> 
> thx,
> Marco


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