From: Vincent Guittot <vincent.guittot@linaro.org> To: peterz@infradead.org, mingo@kernel.org, linux-kernel@vger.kernel.org, preeti@linux.vnet.ibm.com, linux@arm.linux.org.uk, linux-arm-kernel@lists.infradead.org Cc: riel@redhat.com, Morten.Rasmussen@arm.com, efault@gmx.de, nicolas.pitre@linaro.org, linaro-kernel@lists.linaro.org, daniel.lezcano@linaro.org, dietmar.eggemann@arm.com, Vincent Guittot <vincent.guittot@linaro.org> Subject: [PATCH v5 02/12] sched: remove a wake_affine condition Date: Tue, 26 Aug 2014 13:06:45 +0200 [thread overview] Message-ID: <1409051215-16788-3-git-send-email-vincent.guittot@linaro.org> (raw) In-Reply-To: <1409051215-16788-1-git-send-email-vincent.guittot@linaro.org> I have tried to understand the meaning of the condition : (this_load <= load && this_load + target_load(prev_cpu, idx) <= tl_per_task) but i failed to find a use case that can take advantage of it and i haven't found clear description in the previous commits' log. Futhermore, the comment of the condition refers to the task_hot function that was used before being replaced by the current condition: /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and * there is no bad imbalance. */ If we look more deeply the below condition this_load + target_load(prev_cpu, idx) <= tl_per_task When sync is clear, we have : tl_per_task = runnable_load_avg / nr_running this_load = max(runnable_load_avg, cpuload[idx]) target_load = max(runnable_load_avg', cpuload'[idx]) It implies that runnable_load_avg' == 0 and nr_running <= 1 in order to match the condition. This implies that runnable_load_avg == 0 too because of the condition: this_load <= load but if this _load is null, balanced is already set and the test is redundant. If sync is set, it's not as straight forward as above (especially if cgroup are involved) but the policy should be similar as we have removed a task that's going to sleep in order to get a more accurate load and this_load values. The current conclusion is that these additional condition don't give any benefit so we can remove them. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- kernel/sched/fair.c | 30 ++++++------------------------ 1 file changed, 6 insertions(+), 24 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 085e853..87b9dc7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4282,7 +4282,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) { s64 this_load, load; int idx, this_cpu, prev_cpu; - unsigned long tl_per_task; struct task_group *tg; unsigned long weight; int balanced; @@ -4340,32 +4339,15 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) balanced = this_eff_load <= prev_eff_load; } else balanced = true; - - /* - * If the currently running task will sleep within - * a reasonable amount of time then attract this newly - * woken task: - */ - if (sync && balanced) - return 1; - schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); - tl_per_task = cpu_avg_load_per_task(this_cpu); - if (balanced || - (this_load <= load && - this_load + target_load(prev_cpu, idx) <= tl_per_task)) { - /* - * This domain has SD_WAKE_AFFINE and - * p is cache cold in this domain, and - * there is no bad imbalance. - */ - schedstat_inc(sd, ttwu_move_affine); - schedstat_inc(p, se.statistics.nr_wakeups_affine); + if (!balanced) + return 0; - return 1; - } - return 0; + schedstat_inc(sd, ttwu_move_affine); + schedstat_inc(p, se.statistics.nr_wakeups_affine); + + return 1; } /* -- 1.9.1
WARNING: multiple messages have this Message-ID (diff)
From: vincent.guittot@linaro.org (Vincent Guittot) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 02/12] sched: remove a wake_affine condition Date: Tue, 26 Aug 2014 13:06:45 +0200 [thread overview] Message-ID: <1409051215-16788-3-git-send-email-vincent.guittot@linaro.org> (raw) In-Reply-To: <1409051215-16788-1-git-send-email-vincent.guittot@linaro.org> I have tried to understand the meaning of the condition : (this_load <= load && this_load + target_load(prev_cpu, idx) <= tl_per_task) but i failed to find a use case that can take advantage of it and i haven't found clear description in the previous commits' log. Futhermore, the comment of the condition refers to the task_hot function that was used before being replaced by the current condition: /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and * there is no bad imbalance. */ If we look more deeply the below condition this_load + target_load(prev_cpu, idx) <= tl_per_task When sync is clear, we have : tl_per_task = runnable_load_avg / nr_running this_load = max(runnable_load_avg, cpuload[idx]) target_load = max(runnable_load_avg', cpuload'[idx]) It implies that runnable_load_avg' == 0 and nr_running <= 1 in order to match the condition. This implies that runnable_load_avg == 0 too because of the condition: this_load <= load but if this _load is null, balanced is already set and the test is redundant. If sync is set, it's not as straight forward as above (especially if cgroup are involved) but the policy should be similar as we have removed a task that's going to sleep in order to get a more accurate load and this_load values. The current conclusion is that these additional condition don't give any benefit so we can remove them. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> --- kernel/sched/fair.c | 30 ++++++------------------------ 1 file changed, 6 insertions(+), 24 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 085e853..87b9dc7 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4282,7 +4282,6 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) { s64 this_load, load; int idx, this_cpu, prev_cpu; - unsigned long tl_per_task; struct task_group *tg; unsigned long weight; int balanced; @@ -4340,32 +4339,15 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) balanced = this_eff_load <= prev_eff_load; } else balanced = true; - - /* - * If the currently running task will sleep within - * a reasonable amount of time then attract this newly - * woken task: - */ - if (sync && balanced) - return 1; - schedstat_inc(p, se.statistics.nr_wakeups_affine_attempts); - tl_per_task = cpu_avg_load_per_task(this_cpu); - if (balanced || - (this_load <= load && - this_load + target_load(prev_cpu, idx) <= tl_per_task)) { - /* - * This domain has SD_WAKE_AFFINE and - * p is cache cold in this domain, and - * there is no bad imbalance. - */ - schedstat_inc(sd, ttwu_move_affine); - schedstat_inc(p, se.statistics.nr_wakeups_affine); + if (!balanced) + return 0; - return 1; - } - return 0; + schedstat_inc(sd, ttwu_move_affine); + schedstat_inc(p, se.statistics.nr_wakeups_affine); + + return 1; } /* -- 1.9.1
next prev parent reply other threads:[~2014-08-26 11:10 UTC|newest] Thread overview: 164+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-08-26 11:06 [PATCH v5 00/12] sched: consolidation of cpu_capacity Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 01/12] sched: fix imbalance flag reset Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-19 11:47 ` [tip:sched/core] sched: Fix " tip-bot for Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot [this message] 2014-08-26 11:06 ` [PATCH v5 02/12] sched: remove a wake_affine condition Vincent Guittot 2014-09-19 11:47 ` [tip:sched/core] sched: Remove a wake_affine() condition tip-bot for Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 03/12] sched: fix avg_load computation Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-08-30 12:00 ` Preeti U Murthy 2014-08-30 12:00 ` Preeti U Murthy 2014-09-03 11:09 ` Vincent Guittot 2014-09-03 11:09 ` Vincent Guittot 2014-09-03 23:43 ` Tim Chen 2014-09-03 23:43 ` Tim Chen 2014-09-04 7:17 ` Vincent Guittot 2014-09-04 7:17 ` Vincent Guittot 2014-09-04 16:26 ` Tim Chen 2014-09-04 16:26 ` Tim Chen 2014-09-05 11:10 ` Preeti U Murthy 2014-09-05 11:10 ` Preeti U Murthy 2014-09-19 11:47 ` [tip:sched/core] sched: Fix " tip-bot for Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 04/12] sched: Allow all archs to set the capacity_orig Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-08-27 13:12 ` Kamalesh Babulal 2014-08-27 13:12 ` Kamalesh Babulal 2014-08-30 17:07 ` Preeti U Murthy 2014-08-30 17:07 ` Preeti U Murthy 2014-09-01 8:05 ` Vincent Guittot 2014-09-01 8:05 ` Vincent Guittot 2014-09-03 8:41 ` Preeti U Murthy 2014-09-03 8:41 ` Preeti U Murthy 2014-09-10 13:50 ` Peter Zijlstra 2014-09-10 13:50 ` Peter Zijlstra 2014-09-10 14:22 ` Vincent Guittot 2014-09-10 14:22 ` Vincent Guittot 2014-09-11 10:36 ` Preeti U Murthy 2014-09-11 10:36 ` Preeti U Murthy 2014-09-19 11:47 ` [tip:sched/core] sched: Allow all architectures to set ' capacity_orig' tip-bot for Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 05/12] ARM: topology: use new cpu_capacity interface Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-11 18:52 ` Nicolas Pitre 2014-09-11 18:52 ` Nicolas Pitre 2014-09-19 11:48 ` [tip:sched/core] ARM: topology: Use the " tip-bot for Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 06/12] sched: add per rq cpu_capacity_orig Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-08-27 13:32 ` Kamalesh Babulal 2014-08-27 13:32 ` Kamalesh Babulal 2014-08-28 7:34 ` Vincent Guittot 2014-08-28 7:34 ` Vincent Guittot 2014-09-10 13:53 ` Peter Zijlstra 2014-09-10 13:53 ` Peter Zijlstra 2014-09-10 14:19 ` Vincent Guittot 2014-09-10 14:19 ` Vincent Guittot 2014-09-11 19:02 ` Nicolas Pitre 2014-09-11 19:02 ` Nicolas Pitre 2014-09-15 21:22 ` Vincent Guittot 2014-09-15 21:22 ` Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 07/12] sched: test the cpu's capacity in wake affine Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-10 14:19 ` Peter Zijlstra 2014-09-10 14:19 ` Peter Zijlstra 2014-09-19 11:48 ` [tip:sched/core] sched: Test the CPU's capacity in wake_affine() tip-bot for Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 08/12] sched: move cfs task on a CPU with higher capacity Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-08-30 17:50 ` Preeti U Murthy 2014-08-30 17:50 ` Preeti U Murthy 2014-09-01 8:45 ` Vincent Guittot 2014-09-01 8:45 ` Vincent Guittot 2014-09-03 9:11 ` Preeti U Murthy 2014-09-03 9:11 ` Preeti U Murthy 2014-09-03 11:44 ` Vincent Guittot 2014-09-03 11:44 ` Vincent Guittot 2014-09-03 12:26 ` Preeti U Murthy 2014-09-03 12:26 ` Preeti U Murthy 2014-09-03 12:49 ` Vincent Guittot 2014-09-03 12:49 ` Vincent Guittot 2014-09-11 9:27 ` Peter Zijlstra 2014-09-11 9:27 ` Peter Zijlstra 2014-09-05 12:06 ` Preeti U Murthy 2014-09-05 12:06 ` Preeti U Murthy 2014-09-05 12:24 ` Vincent Guittot 2014-09-05 12:24 ` Vincent Guittot 2014-09-11 10:07 ` Peter Zijlstra 2014-09-11 10:07 ` Peter Zijlstra 2014-09-11 11:20 ` Vincent Guittot 2014-09-11 11:20 ` Vincent Guittot 2014-09-11 10:13 ` Peter Zijlstra 2014-09-11 10:13 ` Peter Zijlstra 2014-09-11 12:14 ` Vincent Guittot 2014-09-11 12:14 ` Vincent Guittot 2014-09-11 11:54 ` Peter Zijlstra 2014-09-11 11:54 ` Peter Zijlstra 2014-08-26 11:06 ` [PATCH v5 09/12] sched: add usage_load_avg Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-04 7:34 ` [PATCH v5 09/11] " Vincent Guittot 2014-09-04 7:34 ` Vincent Guittot 2014-09-11 11:17 ` Peter Zijlstra 2014-09-11 11:17 ` Peter Zijlstra 2014-09-11 11:17 ` [PATCH v5 09/12] " Peter Zijlstra 2014-09-11 11:17 ` Peter Zijlstra 2014-09-11 12:18 ` Vincent Guittot 2014-09-11 12:18 ` Vincent Guittot 2014-09-11 12:20 ` Vincent Guittot 2014-09-11 12:20 ` Vincent Guittot 2014-09-15 19:15 ` Morten Rasmussen 2014-09-15 19:15 ` Morten Rasmussen 2014-09-15 22:33 ` Vincent Guittot 2014-09-15 22:33 ` Vincent Guittot 2014-08-26 11:06 ` [PATCH v5 10/12] sched: get CPU's utilization statistic Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-11 12:34 ` Peter Zijlstra 2014-09-11 12:34 ` Peter Zijlstra 2014-09-11 13:07 ` Vincent Guittot 2014-09-11 13:07 ` Vincent Guittot 2014-09-11 14:04 ` Peter Zijlstra 2014-09-11 14:04 ` Peter Zijlstra 2014-09-11 19:17 ` Nicolas Pitre 2014-09-11 19:17 ` Nicolas Pitre 2014-09-12 7:41 ` Vincent Guittot 2014-09-12 7:41 ` Vincent Guittot 2014-09-15 19:45 ` Morten Rasmussen 2014-09-15 19:45 ` Morten Rasmussen 2014-09-16 22:43 ` Vincent Guittot 2014-09-16 22:43 ` Vincent Guittot 2014-09-15 19:28 ` Morten Rasmussen 2014-09-15 19:28 ` Morten Rasmussen 2014-08-26 11:06 ` [PATCH v5 11/12] sched: replace capacity_factor by utilization Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot 2014-09-11 15:39 ` Peter Zijlstra 2014-09-11 15:39 ` Peter Zijlstra 2014-09-11 16:15 ` Peter Zijlstra 2014-09-11 16:15 ` Peter Zijlstra 2014-09-11 17:26 ` Vincent Guittot 2014-09-11 17:26 ` Vincent Guittot 2014-09-14 19:41 ` Peter Zijlstra 2014-09-14 19:41 ` Peter Zijlstra 2014-09-14 19:51 ` Peter Zijlstra 2014-09-14 19:51 ` Peter Zijlstra 2014-09-15 11:42 ` Peter Zijlstra 2014-09-15 11:42 ` Peter Zijlstra 2014-09-15 19:07 ` Nicolas Pitre 2014-09-15 19:07 ` Nicolas Pitre 2014-09-15 20:01 ` Peter Zijlstra 2014-09-15 20:01 ` Peter Zijlstra 2014-09-17 18:45 ` Morten Rasmussen 2014-09-17 18:45 ` Morten Rasmussen 2014-09-17 18:58 ` Morten Rasmussen 2014-09-17 18:58 ` Morten Rasmussen 2014-09-17 23:03 ` Peter Zijlstra 2014-09-17 23:03 ` Peter Zijlstra 2014-09-15 22:14 ` Vincent Guittot 2014-09-15 22:14 ` Vincent Guittot 2014-09-15 22:18 ` Vincent Guittot 2014-09-15 22:18 ` Vincent Guittot 2014-09-17 22:25 ` Peter Zijlstra 2014-09-17 22:25 ` Peter Zijlstra 2014-09-18 1:32 ` Vincent Guittot 2014-09-18 1:32 ` Vincent Guittot 2014-09-16 17:00 ` Dietmar Eggemann 2014-09-16 17:00 ` Dietmar Eggemann 2014-08-26 11:06 ` [PATCH v5 12/12] sched: add SD_PREFER_SIBLING for SMT level Vincent Guittot 2014-08-26 11:06 ` Vincent Guittot
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