From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755270AbbIMLFo (ORCPT ); Sun, 13 Sep 2015 07:05:44 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43555 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753311AbbIMLFm (ORCPT ); Sun, 13 Sep 2015 07:05:42 -0400 Date: Sun, 13 Sep 2015 04:04:51 -0700 From: tip-bot for Dietmar Eggemann Message-ID: Cc: yuyang.du@intel.com, vincent.guittot@linaro.org, morten.rasmussen@arm.com, mingo@kernel.org, daniel.lezcano@linaro.org, linux-kernel@vger.kernel.org, sgurrappadi@nvidia.com, mturquette@baylibre.com, tglx@linutronix.de, dietmar.eggemann@arm.com, rjw@rjwysocki.net, torvalds@linux-foundation.org, hpa@zytor.com, pang.xunlei@zte.com.cn, peterz@infradead.org, Juri.Lelli@arm.com, steve.muckle@linaro.org, efault@gmx.de Reply-To: mturquette@baylibre.com, sgurrappadi@nvidia.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, vincent.guittot@linaro.org, morten.rasmussen@arm.com, yuyang.du@intel.com, mingo@kernel.org, daniel.lezcano@linaro.org, peterz@infradead.org, pang.xunlei@zte.com.cn, Juri.Lelli@arm.com, steve.muckle@linaro.org, efault@gmx.de, dietmar.eggemann@arm.com, rjw@rjwysocki.net, torvalds@linux-foundation.org, hpa@zytor.com In-Reply-To: <55EDAF43.30500@arm.com> References: <55EDAF43.30500@arm.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/core] sched/fair: Get rid of scaling utilization by capacity_orig Git-Commit-ID: 231678b768da07d19ab5683a39eeb0c250631d02 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 231678b768da07d19ab5683a39eeb0c250631d02 Gitweb: http://git.kernel.org/tip/231678b768da07d19ab5683a39eeb0c250631d02 Author: Dietmar Eggemann AuthorDate: Fri, 14 Aug 2015 17:23:13 +0100 Committer: Ingo Molnar CommitDate: Sun, 13 Sep 2015 09:52:57 +0200 sched/fair: Get rid of scaling utilization by capacity_orig 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(). Signed-off-by: Dietmar Eggemann Signed-off-by: Morten Rasmussen Signed-off-by: Peter Zijlstra (Intel) Cc: Juri Lelli Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steve Muckle Cc: Thomas Gleixner Cc: daniel.lezcano@linaro.org Cc: mturquette@baylibre.com Cc: pang.xunlei@zte.com.cn Cc: rjw@rjwysocki.net Cc: sgurrappadi@nvidia.com Cc: vincent.guittot@linaro.org Cc: yuyang.du@intel.com Link: http://lkml.kernel.org/r/55EDAF43.30500@arm.com Signed-off-by: Ingo Molnar --- 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 1b56d63..047fd1c 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4862,33 +4862,39 @@ next: 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; } /*