From: Vincent Guittot <vincent.guittot@linaro.org>
To: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org
Cc: pauld@redhat.com, valentin.schneider@arm.com,
srikar@linux.vnet.ibm.com, quentin.perret@arm.com,
dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com,
hdanton@sina.com, Vincent Guittot <vincent.guittot@linaro.org>
Subject: [PATCH v3 01/10] sched/fair: clean up asym packing
Date: Thu, 19 Sep 2019 09:33:32 +0200 [thread overview]
Message-ID: <1568878421-12301-2-git-send-email-vincent.guittot@linaro.org> (raw)
In-Reply-To: <1568878421-12301-1-git-send-email-vincent.guittot@linaro.org>
Clean up asym packing to follow the default load balance behavior:
- classify the group by creating a group_asym_packing field.
- calculate the imbalance in calculate_imbalance() instead of bypassing it.
We don't need to test twice same conditions anymore to detect asym packing
and we consolidate the calculation of imbalance in calculate_imbalance().
There is no functional changes.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 63 ++++++++++++++---------------------------------------
1 file changed, 16 insertions(+), 47 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1054d2c..3175fea 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7685,6 +7685,7 @@ struct sg_lb_stats {
unsigned int group_weight;
enum group_type group_type;
int group_no_capacity;
+ unsigned int group_asym_packing; /* Tasks should be moved to preferred CPU */
unsigned long group_misfit_task_load; /* A CPU has a task too big for its capacity */
#ifdef CONFIG_NUMA_BALANCING
unsigned int nr_numa_running;
@@ -8139,9 +8140,17 @@ static bool update_sd_pick_busiest(struct lb_env *env,
* ASYM_PACKING needs to move all the work to the highest
* prority CPUs in the group, therefore mark all groups
* of lower priority than ourself as busy.
+ *
+ * This is primarily intended to used at the sibling level. Some
+ * cores like POWER7 prefer to use lower numbered SMT threads. In the
+ * case of POWER7, it can move to lower SMT modes only when higher
+ * threads are idle. When in lower SMT modes, the threads will
+ * perform better since they share less core resources. Hence when we
+ * have idle threads, we want them to be the higher ones.
*/
if (sgs->sum_nr_running &&
sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) {
+ sgs->group_asym_packing = 1;
if (!sds->busiest)
return true;
@@ -8283,51 +8292,6 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
}
/**
- * check_asym_packing - Check to see if the group is packed into the
- * sched domain.
- *
- * This is primarily intended to used at the sibling level. Some
- * cores like POWER7 prefer to use lower numbered SMT threads. In the
- * case of POWER7, it can move to lower SMT modes only when higher
- * threads are idle. When in lower SMT modes, the threads will
- * perform better since they share less core resources. Hence when we
- * have idle threads, we want them to be the higher ones.
- *
- * This packing function is run on idle threads. It checks to see if
- * the busiest CPU in this domain (core in the P7 case) has a higher
- * CPU number than the packing function is being run on. Here we are
- * assuming lower CPU number will be equivalent to lower a SMT thread
- * number.
- *
- * Return: 1 when packing is required and a task should be moved to
- * this CPU. The amount of the imbalance is returned in env->imbalance.
- *
- * @env: The load balancing environment.
- * @sds: Statistics of the sched_domain which is to be packed
- */
-static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds)
-{
- int busiest_cpu;
-
- if (!(env->sd->flags & SD_ASYM_PACKING))
- return 0;
-
- if (env->idle == CPU_NOT_IDLE)
- return 0;
-
- if (!sds->busiest)
- return 0;
-
- busiest_cpu = sds->busiest->asym_prefer_cpu;
- if (sched_asym_prefer(busiest_cpu, env->dst_cpu))
- return 0;
-
- env->imbalance = sds->busiest_stat.group_load;
-
- return 1;
-}
-
-/**
* fix_small_imbalance - Calculate the minor imbalance that exists
* amongst the groups of a sched_domain, during
* load balancing.
@@ -8411,6 +8375,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
local = &sds->local_stat;
busiest = &sds->busiest_stat;
+ if (busiest->group_asym_packing) {
+ env->imbalance = busiest->group_load;
+ return;
+ }
+
if (busiest->group_type == group_imbalanced) {
/*
* In the group_imb case we cannot rely on group-wide averages
@@ -8515,8 +8484,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
busiest = &sds.busiest_stat;
/* ASYM feature bypasses nice load balance check */
- if (check_asym_packing(env, &sds))
- return sds.busiest;
+ if (busiest->group_asym_packing)
+ goto force_balance;
/* There is no busy sibling group to pull tasks from */
if (!sds.busiest || busiest->sum_nr_running == 0)
--
2.7.4
next prev parent reply other threads:[~2019-09-19 7:34 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 7:33 [PATCH v3 0/8] sched/fair: rework the CFS load balance Vincent Guittot
2019-09-19 7:33 ` Vincent Guittot [this message]
2019-09-27 23:57 ` [PATCH v3 01/10] sched/fair: clean up asym packing Rik van Riel
2019-09-19 7:33 ` [PATCH v3 02/10] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-09-27 23:59 ` Rik van Riel
2019-10-01 17:11 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 03/10] sched/fair: remove meaningless imbalance calculation Vincent Guittot
2019-09-28 0:05 ` Rik van Riel
2019-10-01 17:12 ` Valentin Schneider
2019-10-02 6:28 ` Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 04/10] sched/fair: rework load_balance Vincent Guittot
2019-09-30 1:12 ` Rik van Riel
2019-09-30 7:44 ` Vincent Guittot
2019-09-30 16:24 ` Dietmar Eggemann
2019-10-01 8:14 ` Vincent Guittot
2019-10-01 16:52 ` Dietmar Eggemann
2019-10-02 6:44 ` Vincent Guittot
2019-10-02 9:21 ` Dietmar Eggemann
2019-10-08 13:02 ` Peter Zijlstra
2019-10-02 8:23 ` Vincent Guittot
2019-10-02 9:24 ` Dietmar Eggemann
2019-10-01 8:15 ` Dietmar Eggemann
2019-10-01 9:14 ` Vincent Guittot
2019-10-01 16:57 ` Dietmar Eggemann
2019-10-01 17:47 ` Valentin Schneider
2019-10-02 8:30 ` Vincent Guittot
2019-10-02 10:47 ` Valentin Schneider
2019-10-08 14:16 ` Peter Zijlstra
2019-10-08 14:34 ` Valentin Schneider
2019-10-08 15:30 ` Vincent Guittot
2019-10-08 15:48 ` Valentin Schneider
2019-10-08 17:39 ` Peter Zijlstra
2019-10-08 18:45 ` Vincent Guittot
2019-10-08 16:33 ` Peter Zijlstra
2019-10-08 16:39 ` Valentin Schneider
2019-10-08 17:36 ` Valentin Schneider
2019-10-08 17:55 ` Peter Zijlstra
2019-10-08 18:47 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:56 ` Vincent Guittot
2019-10-18 5:34 ` Parth Shah
2019-09-19 7:33 ` [PATCH v3 05/10] sched/fair: use rq->nr_running when balancing load Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 06/10] sched/fair: use load instead of runnable load in load_balance Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 07/10] sched/fair: evenly spread tasks when not overloaded Vincent Guittot
2019-09-19 7:33 ` [PATCH v3 08/10] sched/fair: use utilization to select misfit task Vincent Guittot
2019-10-01 17:12 ` Valentin Schneider
2019-09-19 7:33 ` [PATCH v3 09/10] sched/fair: use load instead of runnable load in wakeup path Vincent Guittot
2019-10-07 15:14 ` Rik van Riel
2019-10-07 15:27 ` Vincent Guittot
2019-10-07 18:06 ` Rik van Riel
2019-09-19 7:33 ` [PATCH v3 10/10] sched/fair: optimize find_idlest_group Vincent Guittot
2019-10-08 14:32 ` [PATCH v3 0/8] sched/fair: rework the CFS load balance Phil Auld
2019-10-08 15:53 ` Vincent Guittot
2019-10-09 19:33 ` Phil Auld
2019-10-10 8:20 ` Vincent Guittot
2019-10-16 7:21 ` Parth Shah
2019-10-16 11:51 ` Vincent Guittot
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