Commit-ID: e0f5f3afd2cffa96291cd852056d83ff4e2e99c7 Gitweb: http://git.kernel.org/tip/e0f5f3afd2cffa96291cd852056d83ff4e2e99c7 Author: Dietmar Eggemann <[email protected]> AuthorDate: Fri, 14 Aug 2015 17:23:09 +0100 Committer: Ingo Molnar <[email protected]> CommitDate: Sun, 13 Sep 2015 09:52:55 +0200
sched/fair: Make load tracking frequency scale-invariant Apply frequency scaling correction factor to per-entity load tracking to make it frequency invariant. Currently, load appears bigger when the CPU is running slower which affects load-balancing decisions. Each segment of the sched_avg.load_sum geometric series is now scaled by the current frequency so that the sched_avg.load_avg of each sched entity will be invariant from frequency scaling. Moreover, cfs_rq.runnable_load_sum is scaled by the current frequency as well. Signed-off-by: Dietmar Eggemann <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Vincent Guittot <[email protected]> Cc: Dietmar Eggemann <[email protected]> Cc: Juri Lelli <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- include/linux/sched.h | 6 +++--- kernel/sched/fair.c | 27 +++++++++++++++++---------- 2 files changed, 20 insertions(+), 13 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index a4ab9da..c8d923b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1177,9 +1177,9 @@ struct load_weight { /* * The load_avg/util_avg accumulates an infinite geometric series. - * 1) load_avg factors the amount of time that a sched_entity is - * runnable on a rq into its weight. For cfs_rq, it is the aggregated - * such weights of all runnable and blocked sched_entities. + * 1) load_avg factors frequency scaling into the amount of time that a + * sched_entity is runnable on a rq into its weight. For cfs_rq, it is the + * aggregated such weights of all runnable and blocked sched_entities. * 2) util_avg factors frequency scaling into the amount of time * that a sched_entity is running on a CPU, in the range [0..SCHED_LOAD_SCALE]. * For cfs_rq, it is the aggregated such times of all runnable and diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 47ece22..86cb27c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2515,6 +2515,8 @@ static u32 __compute_runnable_contrib(u64 n) return contrib + runnable_avg_yN_sum[n]; } +#define scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT) + /* * We can represent the historical contribution to runnable average as the * coefficients of a geometric series. To do this we sub-divide our runnable @@ -2547,9 +2549,9 @@ static __always_inline int __update_load_avg(u64 now, int cpu, struct sched_avg *sa, unsigned long weight, int running, struct cfs_rq *cfs_rq) { - u64 delta, periods; + u64 delta, scaled_delta, periods; u32 contrib; - int delta_w, decayed = 0; + int delta_w, scaled_delta_w, decayed = 0; unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); delta = now - sa->last_update_time; @@ -2585,13 +2587,16 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, * period and accrue it. */ delta_w = 1024 - delta_w; + scaled_delta_w = scale(delta_w, scale_freq); if (weight) { - sa->load_sum += weight * delta_w; - if (cfs_rq) - cfs_rq->runnable_load_sum += weight * delta_w; + sa->load_sum += weight * scaled_delta_w; + if (cfs_rq) { + cfs_rq->runnable_load_sum += + weight * scaled_delta_w; + } } if (running) - sa->util_sum += delta_w * scale_freq >> SCHED_CAPACITY_SHIFT; + sa->util_sum += scaled_delta_w; delta -= delta_w; @@ -2608,23 +2613,25 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, /* Efficiently calculate \sum (1..n_period) 1024*y^i */ contrib = __compute_runnable_contrib(periods); + contrib = scale(contrib, scale_freq); if (weight) { sa->load_sum += weight * contrib; if (cfs_rq) cfs_rq->runnable_load_sum += weight * contrib; } if (running) - sa->util_sum += contrib * scale_freq >> SCHED_CAPACITY_SHIFT; + sa->util_sum += contrib; } /* Remainder of delta accrued against u_0` */ + scaled_delta = scale(delta, scale_freq); if (weight) { - sa->load_sum += weight * delta; + sa->load_sum += weight * scaled_delta; if (cfs_rq) - cfs_rq->runnable_load_sum += weight * delta; + cfs_rq->runnable_load_sum += weight * scaled_delta; } if (running) - sa->util_sum += delta * scale_freq >> SCHED_CAPACITY_SHIFT; + sa->util_sum += scaled_delta; sa->period_contrib += delta; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
