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Date: Thu, 8 Dec 2022 12:39:24 +0100 From: "Rafael J. Wysocki" <rafael@...nel.org> To: "Li,Rongqing" <lirongqing@...du.com> Cc: "Rafael J. Wysocki" <rafael@...nel.org>, "tglx@...utronix.de" <tglx@...utronix.de>, "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>, "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 1/2][v2] cpuidle-haltpoll: Replace default_idle with arch_cpu_idle On Thu, Dec 8, 2022 at 2:48 AM Li,Rongqing <lirongqing@...du.com> wrote: > > > > > -----Original Message----- > > From: Rafael J. Wysocki <rafael@...nel.org> > > Sent: Wednesday, December 7, 2022 10:38 PM > > To: Li,Rongqing <lirongqing@...du.com> > > Cc: tglx@...utronix.de; 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 1/2][v2] cpuidle-haltpoll: Replace default_idle with > > arch_cpu_idle > > > > On Wed, Dec 7, 2022 at 1:42 PM <lirongqing@...du.com> wrote: > > > > > > From: Li RongQing <lirongqing@...du.com> > > > > > > When KVM guest has MWAIT and mwait_idle is used as default idle > > > function, but once cpuidle-haltpoll is loaded, default_idle in > > > default_enter_idle is used, which is using HLT, and cause a > > > performance regression. As the commit aebef63cf7ff ("x86: Remove > > > vendor checks from prefer_mwait_c1_over_halt") explains that mwait is > > > preferred > > > > > > so replace default_idle with arch_cpu_idle which can using MWAIT > > > optimization. > > > > > > latency of sockperf ping-pong localhost test is reduced by more 20% > > > unixbench has 5% performance improvements for single core > > > > > > Suggested-by: Thomas Gleixner <tglx@...utronix.de> > > > Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> > > > Signed-off-by: Li RongQing <lirongqing@...du.com> > > > --- > > > arch/x86/kernel/process.c | 1 + > > > drivers/cpuidle/cpuidle-haltpoll.c | 2 +- > > > 2 files changed, 2 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > > > index c21b734..303afad 100644 > > > --- a/arch/x86/kernel/process.c > > > +++ b/arch/x86/kernel/process.c > > > @@ -721,6 +721,7 @@ void arch_cpu_idle(void) { > > > x86_idle(); > > > } > > > +EXPORT_SYMBOL(arch_cpu_idle); > > > > Why do you need this export at all? > > > > When cpuidle-haltpoll is built as module, But it isn't now. > if arch_cpu_idle is not export, cpuidle-haltpoll will complain "arch_cpu_idle" undefined So no, this won't happen.
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