2017-09-01 14:44 GMT+08:00 Yang Zhang <yang.zhang.wz@xxxxxxxxx>: > On 2017/8/29 22:02, Wanpeng Li wrote: >>> >>> Here is the data we get when running benchmark netperf: >>> >>> 2. w/ patch: >>> halt_poll_threshold=10000 -- 15803.89 bits/s -- 159.5 %CPU >>> halt_poll_threshold=20000 -- 15899.04 bits/s -- 161.5 %CPU >>> halt_poll_threshold=30000 -- 15642.38 bits/s -- 161.8 %CPU >>> halt_poll_threshold=40000 -- 18040.76 bits/s -- 184.0 %CPU >>> halt_poll_threshold=50000 -- 18877.61 bits/s -- 197.3 %CPU >>> >>> 3. kvm dynamic poll >>> halt_poll_ns=10000 -- 15876.00 bits/s -- 172.2 %CPU >>> halt_poll_ns=20000 -- 15602.58 bits/s -- 185.4 %CPU >>> halt_poll_ns=30000 -- 15930.69 bits/s -- 194.4 %CPU >>> halt_poll_ns=40000 -- 16413.09 bits/s -- 195.3 %CPU >>> halt_poll_ns=50000 -- 16417.42 bits/s -- 196.3 %CPU >>> >> >> Actually I'm not sure how much sense it makes to introduce this pv >> stuff and the duplicate adaptive halt-polling logic as what has >> already been done in kvm w/o obvious benefit for real workload like >> netperf. In addition, as you mentioned offline to me, enable both the >> patchset and the adaptive halt-polling logic in kvm simultaneously can >> result in more cpu power consumption. I remembered that David from > > > No.If we use poll in KVM side, it will consume more cpu than in guest side. > If use both two, then we can get the performance as only enable guest side > poll but it will cost more cpu because of poll in KVM side. It means we > should disable KVM side poll since it cannot give much improvement than > guest side except consume more cpu. The customers should have enough knowledge about what's the meaning of the tunning which you exposed. Regards, Wanpeng Li > >> Google mentioned that Windows Event Objects can get 2x latency >> improvement in KVM FORUM, which means that the adaptive halt-polling >> in kvm should be enabled by default. So if the windows guests and >> linux guests are mixed on the same host, then this patchset will >> result in more cpu power consumption if the customer enable the >> polling in the linux guest. Anyway, if the patchset is finally > > > I have said in last time, there already users using idle=poll in there VM, > you *cannot* prevent them doing it. This patch provide a better solution > than unconditional poll, we didn't introduce any worse stuff. > >> acceptable by maintainer, I will introduce the generic adaptive >> halt-polling framework in kvm to avoid the duplicate logic. > > > We will add more conditions than the current algorithm in future. But it's > ok to use one code currently, we will do it in next version. > >> >> Regards, >> Wanpeng Li >> > > > -- > Yang > Alibaba Cloud Computing -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
