From 0c1dc6b27dac883ee78392189c8e20e764d79bfa Mon Sep 17 00:00:00 2001 From: Morten Rasmussen Date: Wed, 4 Mar 2015 08:46:26 +0100 Subject: [PATCH] sched: Make sched entity usage tracking scale-invariant Apply frequency scale-invariance correction factor to usage tracking. Each segment of the running_avg_sum geometric series is now scaled by the current frequency so the utilization_avg_contrib of each entity will be invariant with frequency scaling. As a result, utilization_load_avg which is the sum of utilization_avg_contrib, becomes invariant too. So the usage level that is returned by get_cpu_usage(), stays relative to the max frequency as the cpu_capacity which is is compared against. Then, we want the keep the load tracking values in a 32-bit type, which implies that the max value of {runnable|running}_avg_sum must be lower than 2^32/88761=48388 (88761 is the max weigth of a task). As LOAD_AVG_MAX = 47742, arch_scale_freq_capacity() must return a value less than (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024). So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow. Signed-off-by: Morten Rasmussen Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Cc: Paul Turner Cc: Ben Segall Cc: Ben Segall Cc: Morten.Rasmussen@arm.com Cc: Paul Turner Cc: dietmar.eggemann@arm.com Cc: efault@gmx.de Cc: kamalesh@linux.vnet.ibm.com Cc: linaro-kernel@lists.linaro.org Cc: nicolas.pitre@linaro.org Cc: preeti@linux.vnet.ibm.com Cc: riel@redhat.com Link: http://lkml.kernel.org/r/1425455186-13451-1-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e54231fc6336..7f031e454740 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2484,6 +2484,8 @@ static u32 __compute_runnable_contrib(u64 n) return contrib + runnable_avg_yN_sum[n]; } +unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu); + /* * We can represent the historical contribution to runnable average as the * coefficients of a geometric series. To do this we sub-divide our runnable @@ -2512,7 +2514,7 @@ static u32 __compute_runnable_contrib(u64 n) * load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... ) * = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}] */ -static __always_inline int __update_entity_runnable_avg(u64 now, +static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, struct sched_avg *sa, int runnable, int running) @@ -2520,6 +2522,7 @@ static __always_inline int __update_entity_runnable_avg(u64 now, u64 delta, periods; u32 runnable_contrib; int delta_w, decayed = 0; + unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); delta = now - sa->last_runnable_update; /* @@ -2555,7 +2558,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now, if (runnable) sa->runnable_avg_sum += delta_w; if (running) - sa->running_avg_sum += delta_w; + sa->running_avg_sum += delta_w * scale_freq + >> SCHED_CAPACITY_SHIFT; sa->avg_period += delta_w; delta -= delta_w; @@ -2576,7 +2580,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now, if (runnable) sa->runnable_avg_sum += runnable_contrib; if (running) - sa->running_avg_sum += runnable_contrib; + sa->running_avg_sum += runnable_contrib * scale_freq + >> SCHED_CAPACITY_SHIFT; sa->avg_period += runnable_contrib; } @@ -2584,7 +2589,8 @@ static __always_inline int __update_entity_runnable_avg(u64 now, if (runnable) sa->runnable_avg_sum += delta; if (running) - sa->running_avg_sum += delta; + sa->running_avg_sum += delta * scale_freq + >> SCHED_CAPACITY_SHIFT; sa->avg_period += delta; return decayed; @@ -2692,8 +2698,8 @@ static inline void __update_group_entity_contrib(struct sched_entity *se) static inline void update_rq_runnable_avg(struct rq *rq, int runnable) { - __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable, - runnable); + __update_entity_runnable_avg(rq_clock_task(rq), cpu_of(rq), &rq->avg, + runnable, runnable); __update_tg_runnable_avg(&rq->avg, &rq->cfs); } #else /* CONFIG_FAIR_GROUP_SCHED */ @@ -2771,6 +2777,7 @@ static inline void update_entity_load_avg(struct sched_entity *se, { struct cfs_rq *cfs_rq = cfs_rq_of(se); long contrib_delta, utilization_delta; + int cpu = cpu_of(rq_of(cfs_rq)); u64 now; /* @@ -2782,7 +2789,7 @@ static inline void update_entity_load_avg(struct sched_entity *se, else now = cfs_rq_clock_task(group_cfs_rq(se)); - if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq, + if (!__update_entity_runnable_avg(now, cpu, &se->avg, se->on_rq, cfs_rq->curr == se)) return; -- 2.20.1