Re: [Xen-devel] Poor network performance between DomU with multiqueue support

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 02/12/14 11:53, Zhangleiqiang (Trump) wrote:
> > -----Original Message-----
> > From: xen-devel-bounces@xxxxxxxxxxxxx
> > [mailto:xen-devel-bounces@xxxxxxxxxxxxx] On Behalf Of David Vrabel
> > Sent: Tuesday, December 02, 2014 6:57 PM
> > To: zhangleiqiang; xen-devel@xxxxxxxxxxxxx
> > Subject: Re: [Xen-devel] Poor network performance between DomU with
> > multiqueue support
> >
> > On 02/12/14 08:30, zhangleiqiang wrote:
> > > Hi, all
> > >      I am testing the performance of xen netfront-netback driver that
> > > with multi-queues support. The throughput from domU to remote dom0 is
> > > 9.2Gb/s, but the throughput from domU to remote domU is only 3.6Gb/s,
> > > I think the bottleneck is the throughput from dom0 to local domU.
> > > However, we have done some testing and found the throughput from dom0
> > > to local domU is 5.8Gb/s.
> > >      And if we send packets from one DomU to other 3 DomUs on different
> > > host simultaneously, the sum of throughout can reach 9Gbps. It seems
> > > like the bottleneck is the receiver?
> > >      After some analysis, I found that even the max_queue of
> > > netfront/back is set to 4, there are some strange results as follows:
> > >      1. In domU, only one rx queue deal with softirq
> > >      2. In dom0, only two netback queues process are scheduled, other
> > > two process aren't scheduled.
> > Multiqueue only has benefits if you have multiple flows since the
> > source/destination addresses are hashed to a queue number.  This probably
> > explains why only some of the queues are being used in your test.
> The hash method you mentioned is used for selection of netback process or 
> netfront rx queue?
It's used in both direction to select the queue.

> Indeed, there are 4 netback processes running in Dom0, because there are only 
> one DomU running in Dom0 and so four netback processes are running in Dom0 (the 
> max_queue param of netback kernel module is set to 4).
> The phenomenon is that only 2 of these four netback process were running with 
> about 70% cpu usage, and another two use little CPU.
>
> > David
> >
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