Messages in this thread | | | Subject | Re: [PATCH RFC 0/7] kvm pvtimer | From | Quan Xu <> | Date | Thu, 14 Dec 2017 20:06:14 +0800 |
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On 2017/12/14 19:56, Paolo Bonzini wrote: > 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.
Paolo, could you share the Amazon's patch or the LML link? thanks.
Quan
> Thanks, > > Paolo >
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