On Wed, Feb 02, 2011 at 01:03:05PM -0800, Shirley Ma wrote: > On Wed, 2011-02-02 at 22:17 +0200, Michael S. Tsirkin wrote: > > Well, this is also the only case where the queue is stopped, no? > Yes. I got some debugging data, I saw that sometimes there were so many > packets were waiting for free in guest between vhost_signal & guest xmit > callback. What does this mean? > Looks like the time spent too long from vhost_signal to guest > xmit callback? > > > I tried to accumulate multiple guest to host notifications for TX > > xmits, > > > it did help multiple streams TCP_RR results; > > I don't see a point to delay used idx update, do you? > > It might cause per vhost handle_tx processed more packets. I don't understand. It's a couple of writes - what is the issue? > > So delaying just signal seems better, right? > > I think I need to define the test matrix to collect data for TX xmit > from guest to host here for different tests. > > Data to be collected: > --------------------- > 1. kvm_stat for VM, I/O exits > 2. cpu utilization for both guest and host > 3. cat /proc/interrupts on guest > 4. packets rate from vhost handle_tx per loop > 5. guest netif queue stop rate > 6. how many packets are waiting for free between vhost signaling and > guest callback > 7. performance results > > Test > ---- > 1. TCP_STREAM single stream test for 1K to 4K message size > 2. TCP_RR (64 instance test): 128 - 1K request/response size > > Different hacks > --------------- > 1. Base line data ( with the patch to fix capacity check first, > free_old_xmit_skbs returns number of skbs) > > 2. Drop packet data (will put some debugging in generic networking code) > > 3. Delay guest netif queue wake up until certain descriptors (1/2 ring > size, 1/4 ring size...) are available once the queue has stopped. > > 4. Accumulate more packets per vhost signal in handle_tx? > > 5. 3 & 4 combinations > > 6. Accumulate more packets per guest kick() (TCP_RR) by adding a timer? > > 7. Accumulate more packets per vhost handle_tx() by adding some delay? > > > Haven't noticed that part, how does your patch make it > handle more packets? > > Added a delay in handle_tx(). > > What else? > > It would take sometimes to do this. > > Shirley Need to think about this. -- 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
