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Message-ID: <795f272e68734e52afbe45d876f08dde@baidu.com>
Date: Wed, 7 Dec 2022 12:18:54 +0000
From: "Li,Rongqing" <lirongqing@...du.com>
To: Thomas Gleixner <tglx@...utronix.de>,
"Rafael J. Wysocki" <rafael@...nel.org>
CC: "mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>,
"rafael@...nel.org" <rafael@...nel.org>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"tony.luck@...el.com" <tony.luck@...el.com>,
"jpoimboe@...nel.org" <jpoimboe@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: RE: [PATCH] cpuidle-haltpoll: Disable kvm guest polling when
mwait_idle is used
> -----Original Message-----
> From: Thomas Gleixner <tglx@...utronix.de>
> Sent: Wednesday, December 7, 2022 7:41 PM
> To: Li,Rongqing <lirongqing@...du.com>; Rafael J. Wysocki <rafael@...nel.org>
> Cc: mingo@...hat.com; bp@...en8.de; dave.hansen@...ux.intel.com;
> x86@...nel.org; rafael@...nel.org; daniel.lezcano@...aro.org;
> peterz@...radead.org; akpm@...ux-foundation.org; tony.luck@...el.com;
> jpoimboe@...nel.org; linux-kernel@...r.kernel.org; linux-pm@...r.kernel.org
> Subject: RE: [PATCH] cpuidle-haltpoll: Disable kvm guest polling when
> mwait_idle is used
>
> On Wed, Dec 07 2022 at 10:49, Rongqing Li wrote:
> >> Before change, "sockperf ping-pong -i 127.0.0.1 -p 20001 --tcp " latency is:
> >> sockperf: Summary: Latency is 6.245 usec
> >>
> >> this patch, disable cpuidle-haltpoll
> >> sockperf: Summary: Latency is 4.671 usec
> >>
> >>
> >> using arch_cpu_idle() in default_enter_idle()
> >> sockperf: Summary: Latency is 4.285 usec
> >>
> >
> > When I did upper tests, I taskset sockperf server and client to
> > different cpus, so using arch_cpu_idle() in default_enter_idle() gets
> > better result.
> >
> > I test unixbench also, find that Don't loading cpuidle-haltholl can
> > get more performance on 8 cores (2 threads per core) intel cpu which
> > cstate is disabled in host
> >
> > Don't load cpuidle-haltpoll:
> > System Benchmarks Index Score
> 1995.8
> > System Benchmarks Index Score
> 8482.8
> >
> > Replace default_idle with arch_cpu_idle, and load cpuidle-haltpoll, code like
> below:
> > System Benchmarks Index Score
> 1971.4
> > System Benchmarks Index Score
> 8467.7
> >
> > So I think we should not load cpuidle-haltpoll driver when guest has
> > mwait
>
> So in the above you got:
>
> Driver loaded not modified: 6.245
> Driver not loaded: 4.671 ~25%
> Driver loaded modified: 4.285 ~30%
>
> Now with unixbench:
>
> Driver not loaded: 8482.8
> Driver loaded modified: 8467.7 ~0.2%
>
> So because of 0.2% delta you justify to throw away a 5% win?
>
> If you really care about the 0.2%, then blacklist the module for your use case.
>
Ok, Build it as module by default
Thanks
-Li
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