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Thu, 22 Jul 2021 15:08:01 +0000 Subject: Re: [PATCH] KVM: Consider SMT idle status when halt polling To: Li RongQing , pbonzini@redhat.com, mingo@redhat.com, peterz@infradead.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210722035807.36937-1-lirongqing@baidu.com> From: Dongli Zhang Message-ID: Date: Thu, 22 Jul 2021 08:07:59 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 In-Reply-To: <20210722035807.36937-1-lirongqing@baidu.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SA0PR11CA0093.namprd11.prod.outlook.com (2603:10b6:806:d1::8) To BYAPR10MB2663.namprd10.prod.outlook.com (2603:10b6:a02:a9::20) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [IPv6:2601:646:c303:6700::11e9] (2601:646:c303:6700::11e9) by SA0PR11CA0093.namprd11.prod.outlook.com (2603:10b6:806:d1::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4352.24 via Frontend Transport; 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Thank you very much! Dongli Zhang On 7/21/21 8:58 PM, Li RongQing wrote: > SMT siblings share caches and other hardware, halt polling > will degrade its sibling performance if its sibling is busy > > Signed-off-by: Li RongQing > --- > include/linux/kvm_host.h | 5 ++++- > include/linux/sched.h | 17 +++++++++++++++++ > kernel/sched/fair.c | 17 ----------------- > 3 files changed, 21 insertions(+), 18 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index ae7735b..15b3ef4 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -269,7 +269,10 @@ static inline bool kvm_vcpu_mapped(struct kvm_host_map *map) > > static inline bool kvm_vcpu_can_poll(ktime_t cur, ktime_t stop) > { > - return single_task_running() && !need_resched() && ktime_before(cur, stop); > + return single_task_running() && > + !need_resched() && > + ktime_before(cur, stop) && > + is_core_idle(raw_smp_processor_id()); > } > > /* > diff --git a/include/linux/sched.h b/include/linux/sched.h > index ec8d07d..c333218 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -34,6 +34,7 @@ > #include > #include > #include > +#include > #include > > /* task_struct member predeclarations (sorted alphabetically): */ > @@ -2191,6 +2192,22 @@ int sched_trace_rq_nr_running(struct rq *rq); > > const struct cpumask *sched_trace_rd_span(struct root_domain *rd); > > +static inline bool is_core_idle(int cpu) > +{ > +#ifdef CONFIG_SCHED_SMT > + int sibling; > + > + for_each_cpu(sibling, cpu_smt_mask(cpu)) { > + if (cpu == sibling) > + continue; > + > + if (!idle_cpu(cpu)) > + return false; > + } > +#endif > + return true; > +} > + > #ifdef CONFIG_SCHED_CORE > extern void sched_core_free(struct task_struct *tsk); > extern void sched_core_fork(struct task_struct *p); > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 44c4520..5b0259c 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1477,23 +1477,6 @@ struct numa_stats { > int idle_cpu; > }; > > -static inline bool is_core_idle(int cpu) > -{ > -#ifdef CONFIG_SCHED_SMT > - int sibling; > - > - for_each_cpu(sibling, cpu_smt_mask(cpu)) { > - if (cpu == sibling) > - continue; > - > - if (!idle_cpu(cpu)) > - return false; > - } > -#endif > - > - return true; > -} > - > struct task_numa_env { > struct task_struct *p; > >