Messages in this thread | | | From | "Li,Rongqing" <> | Subject | RE: [PATCH] cpuidle-haltpoll: Disable kvm guest polling when mwait_idle is used | Date | Wed, 7 Dec 2022 12:18:54 +0000 |
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> -----Original Message----- > From: Thomas Gleixner <tglx@linutronix.de> > Sent: Wednesday, December 7, 2022 7:41 PM > To: Li,Rongqing <lirongqing@baidu.com>; Rafael J. Wysocki <rafael@kernel.org> > Cc: mingo@redhat.com; bp@alien8.de; dave.hansen@linux.intel.com; > x86@kernel.org; rafael@kernel.org; daniel.lezcano@linaro.org; > peterz@infradead.org; akpm@linux-foundation.org; tony.luck@intel.com; > jpoimboe@kernel.org; linux-kernel@vger.kernel.org; linux-pm@vger.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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