Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755691AbbHNQUS (ORCPT ); Fri, 14 Aug 2015 12:20:18 -0400 Received: from foss.arm.com ([217.140.101.70]:39334 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755209AbbHNQUN (ORCPT ); Fri, 14 Aug 2015 12:20:13 -0400 From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: vincent.guittot@linaro.org, daniel.lezcano@linaro.org, Dietmar Eggemann , yuyang.du@intel.com, mturquette@baylibre.com, rjw@rjwysocki.net, Juri Lelli , sgurrappadi@nvidia.com, pang.xunlei@zte.com.cn, linux-kernel@vger.kernel.org, Dietmar Eggemann , Morten Rasmussen Subject: [PATCH 3/6] sched/fair: Make utilization tracking cpu scale-invariant Date: Fri, 14 Aug 2015 17:23:11 +0100 Message-Id: <1439569394-11974-4-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1439569394-11974-1-git-send-email-morten.rasmussen@arm.com> References: <1439569394-11974-1-git-send-email-morten.rasmussen@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4901 Lines: 115 From: Dietmar Eggemann Besides the existing frequency scale-invariance correction factor, apply cpu scale-invariance correction factor to utilization tracking to compensate for any differences in compute capacity. This could be due to micro-architectural differences (i.e. instructions per seconds) between cpus in HMP systems (e.g. big.LITTLE), and/or differences in the current maximum frequency supported by individual cpus in SMP systems. In the existing implementation utilization isn't comparable between cpus as it is relative to the capacity of each individual cpu. Each segment of the sched_avg.util_sum geometric series is now scaled by the cpu performance factor too so the sched_avg.util_avg of each sched entity will be invariant from the particular cpu of the HMP/SMP system on which the sched entity is scheduled. With this patch, the utilization of a cpu stays relative to the max cpu performance of the fastest cpu in the system. In contrast to utilization (sched_avg.util_sum), load (sched_avg.load_sum) should not be scaled by compute capacity. The utilization metric is based on running time which only makes sense when cpus are _not_ fully utilized (utilization cannot go beyond 100% even if more tasks are added), where load is runnable time which isn't limited by the capacity of the cpu and therefore is a better metric for overloaded scenarios. If we run two nice-0 busy loops on two cpus with different compute capacity their load should be similar since their compute demands are the same. We have to assume that the compute demand of any task running on a fully utilized cpu (no spare cycles = 100% utilization) is high and the same no matter of the compute capacity of its current cpu, hence we shouldn't scale load by cpu capacity. Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Dietmar Eggemann Signed-off-by: Morten Rasmussen --- include/linux/sched.h | 2 +- kernel/sched/fair.c | 7 ++++--- kernel/sched/sched.h | 2 +- 3 files changed, 6 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index a153051..78a93d7 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1180,7 +1180,7 @@ struct load_weight { * 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 + * 2) util_avg factors frequency and cpu 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 * blocked sched_entities. diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c72223a..63be5a5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2553,6 +2553,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, u32 contrib; int delta_w, scaled_delta_w, decayed = 0; unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); + unsigned long scale_cpu = arch_scale_cpu_capacity(NULL, cpu); delta = now - sa->last_update_time; /* @@ -2596,7 +2597,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, } } if (running) - sa->util_sum += scaled_delta_w; + sa->util_sum = scale(scaled_delta_w, scale_cpu); delta -= delta_w; @@ -2620,7 +2621,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, cfs_rq->runnable_load_sum += weight * contrib; } if (running) - sa->util_sum += contrib; + sa->util_sum += scale(contrib, scale_cpu); } /* Remainder of delta accrued against u_0` */ @@ -2631,7 +2632,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa, cfs_rq->runnable_load_sum += weight * scaled_delta; } if (running) - sa->util_sum += scaled_delta; + sa->util_sum += scale(scaled_delta, scale_cpu); sa->period_contrib += delta; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 7e6f250..50836a9 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1406,7 +1406,7 @@ unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu) static __always_inline unsigned long arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) { - if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1)) + if (sd && (sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1)) return sd->smt_gain / sd->span_weight; return SCHED_CAPACITY_SCALE; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/