On Thu, Apr 08, 2010 at 05:05:42PM -0700, Sridhar Samudrala wrote: > On Mon, 2010-04-05 at 10:35 -0700, Sridhar Samudrala wrote: > > On Sun, 2010-04-04 at 14:14 +0300, Michael S. Tsirkin wrote: > > > On Fri, Apr 02, 2010 at 10:31:20AM -0700, Sridhar Samudrala wrote: > > > > Make vhost scalable by creating a separate vhost thread per vhost > > > > device. This provides better scaling across multiple guests and with > > > > multiple interfaces in a guest. > > > > > > Thanks for looking into this. An alternative approach is > > > to simply replace create_singlethread_workqueue with > > > create_workqueue which would get us a thread per host CPU. > > > > > > It seems that in theory this should be the optimal approach > > > wrt CPU locality, however, in practice a single thread > > > seems to get better numbers. I have a TODO to investigate this. > > > Could you try looking into this? > > > > Yes. I tried using create_workqueue(), but the results were not good > > atleast when the number of guest interfaces is less than the number > > of CPUs. I didn't try more than 8 guests. > > Creating a separate thread per guest interface seems to be more > > scalable based on the testing i have done so far. > > > > I will try some more tests and get some numbers to compare the following > > 3 options. > > - single vhost thread > > - vhost thread per cpu > > - vhost thread per guest virtio interface > > Here are the results with netperf TCP_STREAM 64K guest to host on a > 8-cpu Nehalem system. It shows cumulative bandwidth in Mbps and host > CPU utilization. > > Current default single vhost thread > ----------------------------------- > 1 guest: 12500 37% > 2 guests: 12800 46% > 3 guests: 12600 47% > 4 guests: 12200 47% > 5 guests: 12000 47% > 6 guests: 11700 47% > 7 guests: 11340 47% > 8 guests: 11200 48% > > vhost thread per cpu > -------------------- > 1 guest: 4900 25% > 2 guests: 10800 49% > 3 guests: 17100 67% > 4 guests: 20400 84% > 5 guests: 21000 90% > 6 guests: 22500 92% > 7 guests: 23500 96% > 8 guests: 24500 99% > > vhost thread per guest interface > -------------------------------- > 1 guest: 12500 37% > 2 guests: 21000 72% > 3 guests: 21600 79% > 4 guests: 21600 85% > 5 guests: 22500 89% > 6 guests: 22800 94% > 7 guests: 24500 98% > 8 guests: 26400 99% We can also have a thread per vq. Does it help? > Thanks > Sridhar > -- 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
