On Mon, 6 Jun 2016 14:45:37 +0200 Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > > On 04/06/2016 02:42, Yunhong Jiang wrote: > > It adds a little bit latency for each VM-entry because we need > > setup the preemption timer each time. > > Really it doesn't according to your tests: > > > 1. enable_hv_timer=Y. > > > > 000004 002174 > > 000005 042961 > > 000006 479383 > > 000007 071123 > > 000008 003720 > > > > 2. enable_hv_timer=N. > > > > # Histogram > > ...... > > 000005 000042 > > 000006 000772 > > 000007 008262 > > 000008 200759 > > 000009 381126 > > 000010 008056 > > So perhaps you can replace that paragraph with "The benefits offset > the small extra work to do on each VM-entry to setup the preemption > timer". > > I'll play with this patch and kvm-unit-tests in the next few days. > > David, it would be great if you could also try this on your > message-passing benchmarks (e.g. TCP_RR). On one hand they are heavy > on vmexits, on the other hand they also have many expensive TSC > deadline WRMSRs. I have requested a few small changes, but I am very > happy with the logic and the vmentry cost. > > Thanks, Paolo, thanks for the feedback a lot. I will get a system with TSC scaling and try there, and then will update the patch accordingly. Thanks --jyh > > Paolo -- 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
