Hi RongQing,
Would you mind share if there is any performance data to demonstrate how much
performance can be improved?
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 <lirongqing@xxxxxxxxx>
> ---
> 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;
> + }
> +#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;
>
>
