On Wed, 2011-02-02 at 20:27 +0200, Michael S. Tsirkin wrote: > On Wed, Feb 02, 2011 at 10:11:51AM -0800, Shirley Ma wrote: > > On Wed, 2011-02-02 at 19:32 +0200, Michael S. Tsirkin wrote: > > > OK, but this should have no effect with a vhost patch > > > which should ensure that we don't get an interrupt > > > until the queue is at least half empty. > > > Right? > > > > There should be some coordination between guest and vhost. > > What kind of coordination? With a patched vhost, and a full ring. > you should get an interrupt per 100 packets. > Is this what you see? And if yes, isn't the guest patch > doing nothing then? vhost_signal won't be able send any TX interrupts to guest when guest TX interrupt is disabled. Guest TX interrupt is only enabled when running out of descriptors. > > We shouldn't > > count the TX packets when netif queue is enabled since next guest TX > > xmit will free any used buffers in vhost. We need to be careful here > in > > case we miss the interrupts when netif queue has stopped. > > > > However we can't change old guest so we can test the patches > separately > > for guest only, vhost only, and the combination. > > > > > > > > > > > > Yes, it seems unrelated to tx interrupts. > > > > > > > > The issue is more likely related to latency. > > > > > > Could be. Why do you think so? > > > > Since I played with latency hack, I can see performance difference > for > > different latency. > > Which hack was that? I tried to accumulate multiple guest to host notifications for TX xmits, it did help multiple streams TCP_RR results; I also forced vhost handle_tx to handle more packets; both hack seemed help. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
