From: "Mika Penttilä" <mika.penttila@nextfour.com>
To: Li RongQing <lirongqing@baidu.com>,
pbonzini@redhat.com, mingo@redhat.com, peterz@infradead.org,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: Consider SMT idle status when halt polling
Date: Thu, 22 Jul 2021 07:15:16 +0300 [thread overview]
Message-ID: <a05553b3-7475-c1b8-0282-81ab8b1185c6@nextfour.com> (raw)
In-Reply-To: <20210722035807.36937-1-lirongqing@baidu.com>
On 22.7.2021 6.58, 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 <lirongqing@baidu.com>
> ---
> 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 <linux/rseq.h>
> #include <linux/seqlock.h>
> #include <linux/kcsan.h>
> +#include <linux/topology.h>
> #include <asm/kmap_size.h>
>
> /* 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;
if (!idle_cpu(sibling)) instead, now it returns always 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;
>
next prev parent reply other threads:[~2021-07-22 4:15 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-22 3:58 [PATCH] KVM: Consider SMT idle status when halt polling Li RongQing
2021-07-22 4:15 ` Mika Penttilä [this message]
2021-07-22 5:22 ` 答复: " Li,Rongqing
2021-07-22 5:55 ` Wanpeng Li
2021-07-22 7:10 ` 答复: " Li,Rongqing
2021-07-22 12:16 ` Li,Rongqing
2021-07-27 1:25 ` Sean Christopherson
2021-07-27 6:39 ` 答复: " Li,Rongqing
2021-07-22 13:35 ` kernel test robot
2021-07-22 14:52 ` kernel test robot
2021-07-22 15:07 ` Dongli Zhang
2021-07-22 15:20 ` Dongli Zhang
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