On 2017/9/1 14:58, Wanpeng Li wrote:
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.
We have applied this patch to customize kernel for some real customers
and we get positive feedback from them since the CPU never run at 100%
even there is no task running. Also, this helps them to give more CPUs
to other tasks and reduce the power consumption in their rack. Don't you
think it is better?
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
--
Yang
Alibaba Cloud Computing
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