Re: [PATCH net-next RFC 2/2] vhost_net: basic polling support

On 10/23/2015 12:16 AM, Michael S. Tsirkin wrote:

On Thu, Oct 22, 2015 at 08:46:33AM -0700, Rick Jones wrote:

quoted

On 10/22/2015 02:33 AM, Michael S. Tsirkin wrote:

quoted

On Thu, Oct 22, 2015 at 01:27:29AM -0400, Jason Wang wrote:

quoted

This patch tries to poll for new added tx buffer for a while at the
end of tx processing. The maximum time spent on polling were limited
through a module parameter. To avoid block rx, the loop will end it
there's new other works queued on vhost so in fact socket receive
queue is also be polled.

busyloop_timeout = 50 gives us following improvement on TCP_RR test:

size/session/+thu%/+normalize%
    1/     1/   +5%/  -20%
    1/    50/  +17%/   +3%

Is there a measureable increase in cpu utilization
with busyloop_timeout = 0?

And since a netperf TCP_RR test is involved, be careful about what netperf
reports for CPU util if that increase isn't in the context of the guest OS.

Right, the cpu utilization is measured on host.

quoted

For completeness, looking at the effect on TCP_STREAM and TCP_MAERTS,
aggregate _RR and even aggregate _RR/packets per second for many VMs on the
same system would be in order.

happy benchmarking,

rick jones

Absolutely, merging a new kernel API just for a specific
benchmark doesn't make sense.
I'm guessing this is just an early RFC, a fuller submission
will probably include more numbers.

Yes, will run more complete tests.

Thanks