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% 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
