From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933731AbbELTiB (ORCPT ); Tue, 12 May 2015 15:38:01 -0400 Received: from foss.arm.com ([217.140.101.70]:33731 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933452AbbELThv (ORCPT ); Tue, 12 May 2015 15:37:51 -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 02/34] sched: Make load tracking frequency scale-invariant Date: Tue, 12 May 2015 20:38:37 +0100 Message-Id: <1431459549-18343-3-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 From: Dietmar Eggemann Apply frequency scale-invariance correction factor to load tracking. Each segment of the sched_avg::runnable_avg_sum geometric series is now scaled by the current frequency so the sched_avg::load_avg_contrib of each entity will be invariant with frequency scaling. As a result, cfs_rq::runnable_load_avg which is the sum of sched_avg::load_avg_contrib, becomes invariant too. So the load level that is returned by weighted_cpuload, stays relative to the max frequency of the cpu. Then, we want the keep the load tracking values in a 32bits type, which implies that the max value of sched_avg::{runnable|running}_avg_sum must be lower than 2^32/88761=48388 (88761 is the max weight of a task). As LOAD_AVG_MAX = 47742, arch_scale_freq_capacity must return a value less than (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = 1024). So we define the range to [0..SCHED_SCALE_CAPACITY] in order to avoid overflow. Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Dietmar Eggemann Acked-by: Vincent Guittot --- kernel/sched/fair.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f18ddb7..5eccd63 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2536,9 +2536,9 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, int runnable, int running) { - u64 delta, periods; - u32 runnable_contrib; - int delta_w, decayed = 0; + u64 delta, scaled_delta, periods; + u32 runnable_contrib, scaled_runnable_contrib; + int delta_w, scaled_delta_w, decayed = 0; unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); delta = now - sa->last_runnable_update; @@ -2572,11 +2572,12 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, * period and accrue it. */ delta_w = 1024 - delta_w; + scaled_delta_w = (delta_w * scale_freq) >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += delta_w; + sa->runnable_avg_sum += scaled_delta_w; if (running) - sa->running_avg_sum += delta_w * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_delta_w; sa->avg_period += delta_w; delta -= delta_w; @@ -2594,20 +2595,23 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, /* Efficiently calculate \sum (1..n_period) 1024*y^i */ runnable_contrib = __compute_runnable_contrib(periods); + scaled_runnable_contrib = (runnable_contrib * scale_freq) + >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += runnable_contrib; + sa->runnable_avg_sum += scaled_runnable_contrib; if (running) - sa->running_avg_sum += runnable_contrib * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_runnable_contrib; sa->avg_period += runnable_contrib; } /* Remainder of delta accrued against u_0` */ + scaled_delta = (delta * scale_freq) >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += delta; + sa->runnable_avg_sum += scaled_delta; if (running) - sa->running_avg_sum += delta * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_delta; sa->avg_period += delta; return decayed; -- 1.9.1