On 13/12/2017 17:28, Konrad Rzeszutek Wilk wrote: > 1) VM idle path and network req/resp services: > > Does this go away if you don't hit the idle path? Meaning if you > loop without hitting HLT/MWAIT? I am assuming the issue you are facing > is the latency - that is first time the guest comes from HLT and > responds to the packet the latency is much higher than without? > > And the arming of the timer? > 2) process context switches. > > Is that related to the 1)? That is the 'schedule' call and the process > going to sleep waiting for an interrupt or timer? > > This all sounds like issues with low-CPU usage workloads where you > need low latency responses? Even high-CPU usage, as long as there is a small idle time. The cost of setting the TSC deadline timer twice is about 3000 cycles. However, I think Amazon's approach of not intercepting HLT/MWAIT/PAUSE can recover most of the performance and it's way less intrusive. Thanks, Paolo
