From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753322Ab3LCJIB (ORCPT ); Tue, 3 Dec 2013 04:08:01 -0500 Received: from mail-pa0-f42.google.com ([209.85.220.42]:46572 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753237Ab3LCJH3 (ORCPT ); Tue, 3 Dec 2013 04:07:29 -0500 From: Alex Shi To: mingo@redhat.com, peterz@infradead.org, morten.rasmussen@arm.com, vincent.guittot@linaro.org, daniel.lezcano@linaro.org, fweisbec@gmail.com, linux@arm.linux.org.uk, tony.luck@intel.com, fenghua.yu@intel.com, tglx@linutronix.de, akpm@linux-foundation.org, arjan@linux.intel.com, pjt@google.com, fengguang.wu@intel.com Cc: james.hogan@imgtec.com, alex.shi@linaro.org, jason.low2@hp.com, gregkh@linuxfoundation.org, hanjun.guo@linaro.org, linux-kernel@vger.kernel.org Subject: [PATCH 4/4] sched: bias to target cpu load to reduce task moving Date: Tue, 3 Dec 2013 17:05:56 +0800 Message-Id: <1386061556-28233-5-git-send-email-alex.shi@linaro.org> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1386061556-28233-1-git-send-email-alex.shi@linaro.org> References: <1386061556-28233-1-git-send-email-alex.shi@linaro.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Task migration happens when target just a bit less then source cpu load. To reduce such situation happens, aggravate the target cpu load with sd->imbalance_pct/100. This patch removes the hackbench thread regression on Daniel's Intel Core2 server. a5d6e63 +patch1~3 +patch1~4 hackbench -T -s 4096 -l 1000 -g 10 -f 40 27.914" 38.694" 28.587" 28.390" 38.341" 29.513" 28.048" 38.626" 28.706" Signed-off-by: Alex Shi --- kernel/sched/fair.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index bccdd89..c49b7ba 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -978,7 +978,7 @@ static inline unsigned long group_weight(struct task_struct *p, int nid) static unsigned long weighted_cpuload(const int cpu); static unsigned long source_load(int cpu); -static unsigned long target_load(int cpu); +static unsigned long target_load(int cpu, int imbalance_pct); static unsigned long power_of(int cpu); static long effective_load(struct task_group *tg, int cpu, long wl, long wg); @@ -3809,11 +3809,17 @@ static unsigned long source_load(int cpu) * Return a high guess at the load of a migration-target cpu weighted * according to the scheduling class and "nice" value. */ -static unsigned long target_load(int cpu) +static unsigned long target_load(int cpu, int imbalance_pct) { struct rq *rq = cpu_rq(cpu); unsigned long total = weighted_cpuload(cpu); + /* + * without cpu_load decay, in most of time cpu_load is same as total + * so we need to make target a bit heavier to reduce task migration + */ + total = total * imbalance_pct / 100; + if (!sched_feat(LB_BIAS)) return total; @@ -4033,7 +4039,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) this_cpu = smp_processor_id(); prev_cpu = task_cpu(p); load = source_load(prev_cpu); - this_load = target_load(this_cpu); + this_load = target_load(this_cpu, 100); /* * If sync wakeup then subtract the (maximum possible) @@ -4089,7 +4095,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) if (balanced || (this_load <= load && - this_load + target_load(prev_cpu) <= tl_per_task)) { + this_load + target_load(prev_cpu, 100) <= tl_per_task)) { /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and @@ -4135,7 +4141,7 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu) if (local_group) load = source_load(i); else - load = target_load(i); + load = target_load(i, sd->imbalance_pct); avg_load += load; } @@ -5478,7 +5484,7 @@ static inline void update_sg_lb_stats(struct lb_env *env, /* Bias balancing toward cpus of our domain */ if (local_group) - load = target_load(i); + load = target_load(i, env->sd->imbalance_pct); else load = source_load(i); -- 1.8.1.2