Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755712AbbHNQUY (ORCPT ); Fri, 14 Aug 2015 12:20:24 -0400 Received: from foss.arm.com ([217.140.101.70]:39354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755692AbbHNQUT (ORCPT ); Fri, 14 Aug 2015 12:20:19 -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 5/6] sched/fair: Get rid of scaling utilization by capacity_orig Date: Fri, 14 Aug 2015 17:23:13 +0100 Message-Id: <1439569394-11974-6-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: 3822 Lines: 83 From: Dietmar Eggemann Utilization is currently scaled by capacity_orig, but since we now have frequency and cpu invariant cfs_rq.avg.util_avg, frequency and cpu scaling now happens as part of the utilization tracking itself. So cfs_rq.avg.util_avg should no longer be scaled in cpu_util(). Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Dietmar Eggemann Signed-off-by: Morten Rasmussen --- kernel/sched/fair.c | 38 ++++++++++++++++++++++---------------- 1 file changed, 22 insertions(+), 16 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 4cc3050..34e24181 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4824,33 +4824,39 @@ static int select_idle_sibling(struct task_struct *p, int target) done: return target; } + /* * cpu_util returns the amount of capacity of a CPU that is used by CFS * tasks. The unit of the return value must be the one of capacity so we can * compare the utilization with the capacity of the CPU that is available for * CFS task (ie cpu_capacity). - * cfs.avg.util_avg is the sum of running time of runnable tasks on a - * CPU. It represents the amount of utilization of a CPU in the range - * [0..SCHED_LOAD_SCALE]. The utilization of a CPU can't be higher than the - * full capacity of the CPU because it's about the running time on this CPU. - * Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE - * because of unfortunate rounding in util_avg or just - * after migrating tasks until the average stabilizes with the new running - * time. So we need to check that the utilization stays into the range - * [0..cpu_capacity_orig] and cap if necessary. - * Without capping the utilization, a group could be seen as overloaded (CPU0 - * utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of - * available capacity. + * + * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the + * recent utilization of currently non-runnable tasks on a CPU. It represents + * the amount of utilization of a CPU in the range [0..capacity_orig] where + * capacity_orig is the cpu_capacity available at * the highest frequency + * (arch_scale_freq_capacity()). + * The utilization of a CPU converges towards a sum equal to or less than the + * current capacity (capacity_curr <= capacity_orig) of the CPU because it is + * the running time on this CPU scaled by capacity_curr. + * + * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even + * higher than capacity_orig because of unfortunate rounding in + * cfs.avg.util_avg or just after migrating tasks and new task wakeups until + * the average stabilizes with the new running time. We need to check that the + * utilization stays within the range of [0..capacity_orig] and cap it if + * necessary. Without utilization capping, a group could be seen as overloaded + * (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of + * available capacity. We allow utilization to overshoot capacity_curr (but not + * capacity_orig) as it useful for predicting the capacity required after task + * migrations (scheduler-driven DVFS). */ static int cpu_util(int cpu) { unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg; unsigned long capacity = capacity_orig_of(cpu); - if (util >= SCHED_LOAD_SCALE) - return capacity; - - return (util * capacity) >> SCHED_LOAD_SHIFT; + return (util >= capacity) ? capacity : util; } /* -- 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/