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Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support

From Yang Zhang <yang.zhang.wz@gmail.com>
Newsgroups linux.kernel
Subject Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support
Date 2017-09-01 08:50 +0200
Message-ID <ukNWa-9F-7@gated-at.bofh.it> (permalink)
References <ujNbP-25K-5@gated-at.bofh.it> <ujPnk-3Ci-21@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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.

> 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

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[RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
  [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle path Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
    Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle  path Peter Zijlstra <peterz@infradead.org> - 2017-08-29 14:50 +0200
      Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle  path Quan Xu <quan.xu0@gmail.com> - 2017-09-01 08:00 +0200
    Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle  path Borislav Petkov <bp@alien8.de> - 2017-08-29 16:40 +0200
      Re: [RFC PATCH v2 3/7] sched/idle: Add poll before enter real idle  path Quan Xu <quan.xu0@gmail.com> - 2017-09-01 09:00 +0200
  [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
    Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2017-08-29 16:10 +0200
      Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Juergen Gross <jgross@suse.com> - 2017-08-30 09:40 +0200
      Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 09:00 +0200
  [RFC PATCH v2 5/7] Documentation: Add three sysctls for smart idle poll Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
    Re: [RFC PATCH v2 5/7] Documentation: Add three sysctls for smart  idle poll "Luis R. Rodriguez" <mcgrof@kernel.org> - 2017-08-29 19:30 +0200
  [RFC PATCH v2 2/7] KVM guest: register kvm_idle_poll for pv_idle_ops Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
  [RFC PATCH v2 4/7] x86/paravirt: Add update in x86/paravirt pv_idle_ops Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
  [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from idle Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-29 13:50 +0200
    Re: [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from  idle Peter Zijlstra <peterz@infradead.org> - 2017-08-29 14:50 +0200
      Re: [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from  idle Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 09:40 +0200
  Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Alexander Graf <agraf@suse.de> - 2017-08-29 14:00 +0200
    Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 08:30 +0200
  Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Andi Kleen <andi@firstfloor.org> - 2017-08-29 15:10 +0200
  Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Wanpeng Li <kernellwp@gmail.com> - 2017-08-29 16:10 +0200
    Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2017-08-29 16:30 +0200
    Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-29 16:40 +0200
    Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 08:40 +0200
      Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Wanpeng Li <kernellwp@gmail.com> - 2017-09-01 09:00 +0200
    Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 08:50 +0200
      Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Wanpeng Li <kernellwp@gmail.com> - 2017-09-01 09:00 +0200
        Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support Yang Zhang <yang.zhang.wz@gmail.com> - 2017-09-01 10:00 +0200
  Re: [RFC PATCH v2 0/7] x86/idle: add halt poll support "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-29 17:00 +0200

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