Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933764AbbELTiH (ORCPT ); Tue, 12 May 2015 15:38:07 -0400 Received: from foss.arm.com ([217.140.101.70]:33773 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933733AbbELTiC (ORCPT ); Tue, 12 May 2015 15:38:02 -0400 From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: vincent.guittot@linaro.org, Dietmar Eggemann , yuyang.du@intel.com, preeti@linux.vnet.ibm.com, mturquette@linaro.org, rjw@rjwysocki.net, Juri Lelli , sgurrappadi@nvidia.com, pang.xunlei@zte.com.cn, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, morten.rasmussen@arm.com Subject: [RFCv4 PATCH 06/34] sched: Make usage tracking cpu scale-invariant Date: Tue, 12 May 2015 20:38:41 +0100 Message-Id: <1431459549-18343-7-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1431459549-18343-1-git-send-email-morten.rasmussen@arm.com> References: <1431459549-18343-1-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: 4191 Lines: 113 From: Dietmar Eggemann Besides the existing frequency scale-invariance correction factor, apply cpu scale-invariance correction factor to usage tracking. Cpu scale-invariance takes cpu performance deviations due to micro-architectural differences (i.e. instructions per seconds) between cpus in HMP systems (e.g. big.LITTLE) and differences in the frequency value of the highest OPP between cpus in SMP systems into consideration. Each segment of the sched_avg::running_avg_sum geometric series is now scaled by the cpu performance factor too so the sched_avg::utilization_avg_contrib of each entity will be invariant from the particular cpu of the HMP/SMP system it is gathered on. So the usage level that is returned by get_cpu_usage stays relative to the max cpu performance of the system. In contrast to usage, load (sched_avg::runnable_avg_sum) is currently not considered to be made cpu scale-invariant because this will have a negative effect on the the existing load balance code based on s[dg]_lb_stats::avg_load in overload scenarios. example: 7 always running tasks 4 on cluster 0 (2 cpus w/ cpu_capacity=512) 3 on cluster 1 (1 cpu w/ cpu_capacity=1024) cluster 0 cluster 1 capacity 1024 (2*512) 1024 (1*1024) load 4096 3072 cpu-scaled load 2048 3072 Simply using cpu-scaled load in the existing lb code would declare cluster 1 busier than cluster 0, although the compute capacity budget for one task is higher on cluster 1 (1024/3 = 341) than on cluster 0 (2*512/4 = 256). Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Dietmar Eggemann --- kernel/sched/fair.c | 13 +++++++++++++ kernel/sched/sched.h | 2 +- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d71d0ca..af55982 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2540,6 +2540,7 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, u32 runnable_contrib, scaled_runnable_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_runnable_update; /* @@ -2576,6 +2577,10 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, if (runnable) sa->runnable_avg_sum += scaled_delta_w; + + scaled_delta_w *= scale_cpu; + scaled_delta_w >>= SCHED_CAPACITY_SHIFT; + if (running) sa->running_avg_sum += scaled_delta_w; sa->avg_period += delta_w; @@ -2600,6 +2605,10 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, if (runnable) sa->runnable_avg_sum += scaled_runnable_contrib; + + scaled_runnable_contrib *= scale_cpu; + scaled_runnable_contrib >>= SCHED_CAPACITY_SHIFT; + if (running) sa->running_avg_sum += scaled_runnable_contrib; sa->avg_period += runnable_contrib; @@ -2610,6 +2619,10 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, if (runnable) sa->runnable_avg_sum += scaled_delta; + + scaled_delta *= scale_cpu; + scaled_delta >>= SCHED_CAPACITY_SHIFT; + if (running) sa->running_avg_sum += scaled_delta; sa->avg_period += delta; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index b422e08..3193025 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1404,7 +1404,7 @@ 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/