Messages in this thread Patch in this message | | | From | Chen Yu <> | Subject | [RFC PATCH 3/7] sched/fair: Save a snapshot of sched domain total_load and total_capacity | Date | Thu, 27 Jul 2023 22:34:50 +0800 |
| |
Save the total_load, total_capacity of the current sched domain in each periodic load balance. This statistic can be used later by CPU_NEWLY_IDLE load balance if it quits the scan earlier. Introduce a sched feature ILB_SNAPSHOT to control this. Code can check if sd_share->total_capacity is non-zero to verify if the stat is valid.
In theory, if the system has reached a stable status, the total_capacity and total_load should not change dramatically.
Signed-off-by: Chen Yu <yu.c.chen@intel.com> --- include/linux/sched/topology.h | 2 ++ kernel/sched/fair.c | 25 +++++++++++++++++++++++++ kernel/sched/features.h | 2 ++ 3 files changed, 29 insertions(+)
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index c07f2f00317a..d6a64a2c92aa 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -82,6 +82,8 @@ struct sched_domain_shared { atomic_t nr_busy_cpus; int has_idle_cores; int nr_idle_scan; + unsigned long total_load; + unsigned long total_capacity; }; struct sched_domain { diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index b3e25be58e2b..edcfee9965cd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10132,6 +10132,27 @@ static void update_idle_cpu_scan(struct lb_env *env, WRITE_ONCE(sd_share->nr_idle_scan, (int)y); } +static void ilb_save_stats(struct lb_env *env, + struct sched_domain_shared *sd_share, + struct sd_lb_stats *sds) +{ + if (!sched_feat(ILB_SNAPSHOT)) + return; + + if (!sd_share) + return; + + /* newidle balance is too frequent */ + if (env->idle == CPU_NEWLY_IDLE) + return; + + if (sds->total_load != sd_share->total_load) + WRITE_ONCE(sd_share->total_load, sds->total_load); + + if (sds->total_capacity != sd_share->total_capacity) + WRITE_ONCE(sd_share->total_capacity, sds->total_capacity); +} + /** * update_sd_lb_stats - Update sched_domain's statistics for load balancing. * @env: The load balancing environment. @@ -10140,6 +10161,7 @@ static void update_idle_cpu_scan(struct lb_env *env, static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sds) { + struct sched_domain_shared *sd_share = env->sd->shared; struct sched_group *sg = env->sd->groups; struct sg_lb_stats *local = &sds->local_stat; struct sg_lb_stats tmp_sgs; @@ -10209,6 +10231,9 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd } update_idle_cpu_scan(env, sum_util); + + /* save a snapshot of stats during periodic load balance */ + ilb_save_stats(env, sd_share, sds); } /** diff --git a/kernel/sched/features.h b/kernel/sched/features.h index ee7f23c76bd3..3cb71c8cddc0 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -101,3 +101,5 @@ SCHED_FEAT(LATENCY_WARN, false) SCHED_FEAT(ALT_PERIOD, true) SCHED_FEAT(BASE_SLICE, true) + +SCHED_FEAT(ILB_SNAPSHOT, true) -- 2.25.1
| |