Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1162225AbbBDSng (ORCPT ); Wed, 4 Feb 2015 13:43:36 -0500 Received: from foss-mx-na.foss.arm.com ([217.140.108.86]:41539 "EHLO foss-mx-na.foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161547AbbBDSax (ORCPT ); Wed, 4 Feb 2015 13:30:53 -0500 From: Morten Rasmussen To: peterz@infradead.org, mingo@redhat.com Cc: vincent.guittot@linaro.org, dietmar.eggemann@arm.com, yuyang.du@intel.com, preeti@linux.vnet.ibm.com, mturquette@linaro.org, nico@linaro.org, rjw@rjwysocki.net, juri.lelli@arm.com, linux-kernel@vger.kernel.org Subject: [RFCv3 PATCH 11/48] sched: Make load tracking frequency scale-invariant Date: Wed, 4 Feb 2015 18:30:48 +0000 Message-Id: <1423074685-6336-12-git-send-email-morten.rasmussen@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1423074685-6336-1-git-send-email-morten.rasmussen@arm.com> References: <1423074685-6336-1-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: 3661 Lines: 97 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 bd73f26..e9a26b1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2507,9 +2507,9 @@ 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; @@ -2543,11 +2543,12 @@ 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; @@ -2565,20 +2566,23 @@ 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 -- 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/