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Message-Id: <a1ec30f98c143bc4dea3c18827f72944331d0a9e.1682661027.git.yu.c.chen@intel.com>
Date: Sat, 29 Apr 2023 07:16:41 +0800
From: Chen Yu <yu.c.chen@...el.com>
To: Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Ingo Molnar <mingo@...hat.com>,
Juri Lelli <juri.lelli@...hat.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>,
Tim Chen <tim.c.chen@...el.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>,
K Prateek Nayak <kprateek.nayak@....com>,
Abel Wu <wuyun.abel@...edance.com>,
Yicong Yang <yangyicong@...ilicon.com>,
"Gautham R . Shenoy" <gautham.shenoy@....com>,
Honglei Wang <wanghonglei@...ichuxing.com>,
Len Brown <len.brown@...el.com>,
Chen Yu <yu.chen.surf@...il.com>,
Tianchen Ding <dtcccc@...ux.alibaba.com>,
Joel Fernandes <joel@...lfernandes.org>,
Josh Don <joshdon@...gle.com>,
kernel test robot <yujie.liu@...el.com>,
Arjan Van De Ven <arjan.van.de.ven@...el.com>,
Aaron Lu <aaron.lu@...el.com>, linux-kernel@...r.kernel.org,
Chen Yu <yu.c.chen@...el.com>
Subject: [PATCH v8 1/2] sched/fair: Record the average duration of a task
Record the average duration of a task, as there is a requirement
to leverage this information for better task placement.
At first thought the (p->se.sum_exec_runtime / p->nvcsw)
can be used to measure the task duration. However, the
history long past was factored too heavily in such a formula.
Ideally, the old activity should decay and not affect
the current status too much.
Although something based on PELT can be used, se.util_avg might
not be appropriate to describe the task duration:
Task p1 and task p2 are doing frequent ping-pong scheduling on
one CPU, both p1 and p2 have a short duration, but the util_avg
of each task can be up to 50%, which is inconsistent with the
short task duration.
It was found that there was once a similar feature to track the
duration of a task:
commit ad4b78bbcbab ("sched: Add new wakeup preemption mode: WAKEUP_RUNNING")
Unfortunately, it was reverted because it was an experiment. Pick the
patch up again, by recording the average duration when a task voluntarily
switches out.
Suppose on CPU1, task p1 and p2 run alternatively:
--------------------> time
| p1 runs 1ms | p2 preempt p1 | p1 switch in, runs 0.5ms and blocks |
^ ^ ^
|_____________| |_____________________________________|
^
|
p1 dequeued
p1's duration in one section is (1 + 0.5)ms. Because if p2 does not
preempt p1, p1 can run 1.5ms. This reflects the nature of a task:
how long it wishes to run at most.
Suggested-by: Tim Chen <tim.c.chen@...el.com>
Suggested-by: Vincent Guittot <vincent.guittot@...aro.org>
Tested-by: K Prateek Nayak <kprateek.nayak@....com>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
include/linux/sched.h | 3 +++
kernel/sched/core.c | 2 ++
kernel/sched/debug.c | 1 +
kernel/sched/fair.c | 13 +++++++++++++
4 files changed, 19 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 675298d6eb36..6ee6b00faa12 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -558,6 +558,9 @@ struct sched_entity {
u64 prev_sum_exec_runtime;
u64 nr_migrations;
+ u64 prev_sleep_sum_runtime;
+ /* average duration of a task */
+ u64 dur_avg;
#ifdef CONFIG_FAIR_GROUP_SCHED
int depth;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 898fa3bc2765..32eacd220e39 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4452,6 +4452,8 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
p->se.prev_sum_exec_runtime = 0;
p->se.nr_migrations = 0;
p->se.vruntime = 0;
+ p->se.dur_avg = 0;
+ p->se.prev_sleep_sum_runtime = 0;
INIT_LIST_HEAD(&p->se.group_node);
#ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..8d64fba16cfe 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -1024,6 +1024,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns,
__PS("nr_involuntary_switches", p->nivcsw);
P(se.load.weight);
+ P(se.dur_avg);
#ifdef CONFIG_SMP
P(se.avg.load_sum);
P(se.avg.runnable_sum);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3f8135d7c89d..3236011658a2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6319,6 +6319,18 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
static void set_next_buddy(struct sched_entity *se);
+static inline void dur_avg_update(struct task_struct *p, bool task_sleep)
+{
+ u64 dur;
+
+ if (!task_sleep)
+ return;
+
+ dur = p->se.sum_exec_runtime - p->se.prev_sleep_sum_runtime;
+ p->se.prev_sleep_sum_runtime = p->se.sum_exec_runtime;
+ update_avg(&p->se.dur_avg, dur);
+}
+
/*
* The dequeue_task method is called before nr_running is
* decreased. We remove the task from the rbtree and
@@ -6391,6 +6403,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
dequeue_throttle:
util_est_update(&rq->cfs, p, task_sleep);
+ dur_avg_update(p, task_sleep);
hrtick_update(rq);
}
--
2.25.1
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