Apply frequency scale-invariance correction factor to usage tracking. Each segment of the running_load_avg 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 32bits 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.
cc: Paul Turner pjt@google.com cc: Ben Segall bsegall@google.com
Signed-off-by: Morten Rasmussen morten.rasmussen@arm.com Signed-off-by: Vincent Guittot vincent.guittot@linaro.org --- kernel/sched/fair.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 60c3172..c09df87 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2471,6 +2471,8 @@ static u32 __compute_runnable_contrib(u64 n) return contrib + runnable_avg_yN_sum[n]; }
+unsigned long __weak arch_scale_freq_capacity(int cpu, unsigned long factor); + /* * We can represent the historical contribution to runnable average as the * coefficients of a geometric series. To do this we sub-divide our runnable @@ -2499,7 +2501,7 @@ 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) @@ -2542,7 +2544,8 @@ 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 += + arch_scale_freq_capacity(cpu, delta_w); sa->avg_period += delta_w;
delta -= delta_w; @@ -2563,7 +2566,8 @@ 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 += + arch_scale_freq_capacity(cpu, runnable_contrib); sa->avg_period += runnable_contrib; }
@@ -2571,7 +2575,7 @@ 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 += arch_scale_freq_capacity(cpu, delta); sa->avg_period += delta;
return decayed; @@ -2679,8 +2683,8 @@ 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 */ @@ -2758,6 +2762,7 @@ 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;
/* @@ -2769,7 +2774,7 @@ 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;