Re: Poor network performance between DomU with multiqueue support

[David Vrabel <david.vrabel@citrix.com>]

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.

David