On 09/02/2013 02:30 PM, Jason Wang wrote:

On 09/02/2013 01:56 PM, Michael S. Tsirkin wrote:

quoted

quoted

On Fri, Aug 30, 2013 at 12:29:22PM +0800, Jason Wang wrote:

quoted

quoted

As Michael point out, We used to limit the max pending DMAs to get better cache
utilization. But it was not done correctly since it was one done when there's no
new buffers submitted from guest. Guest can easily exceeds the limitation by
keeping sending packets.

So this patch moves the check into main loop. Tests shows about 5%-10%
improvement on per cpu throughput for guest tx. But a 5% drop on per cpu
transaction rate for a single session TCP_RR.

Any explanation for the drop? single session TCP_RR is unlikely to
exceed VHOST_MAX_PEND, correct?

Unlikely to exceed. Recheck the result, looks like it was not stable
enough. Will re-test and report.

Re-tested with more iterations, result shows no difference on TCP_RR
test and 5%-10% improvement on per cpu throughput for guest tx.

Will post V3 soon.