From: Juri Lelli <juri.lelli@redhat.com>
To: peterz@infradead.org, mingo@redhat.com
Cc: rostedt@goodmis.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, luca.abeni@santannapisa.it,
tommaso.cucinotta@santannapisa.it, alessio.balsini@gmail.com,
bristot@redhat.com, dietmar.eggemann@arm.com,
linux-rt-users@vger.kernel.org, mtosatti@redhat.com,
williams@redhat.com, valentin.schneider@arm.com
Subject: [RFC PATCH v2 5/6] sched/fair: Add trivial fair server
Date: Fri, 7 Aug 2020 11:50:50 +0200 [thread overview]
Message-ID: <20200807095051.385985-6-juri.lelli@redhat.com> (raw)
In-Reply-To: <20200807095051.385985-1-juri.lelli@redhat.com>
From: Peter Zijlstra <peterz@infradead.org>
Use deadline servers to service fair tasks.
This patch adds a fair_server deadline entity which acts as a container
for fair entities and can be used to fix starvation when higher priority
(wrt fair) tasks are monopolizing CPU(s).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/core.c | 1 +
kernel/sched/fair.c | 29 +++++++++++++++++++++++++++++
kernel/sched/sched.h | 4 ++++
3 files changed, 34 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7c471961fd0b8..6537637139c63 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7170,6 +7170,7 @@ void __init sched_init(void)
#endif /* CONFIG_SMP */
hrtick_rq_init(rq);
atomic_set(&rq->nr_iowait, 0);
+ fair_server_init(rq);
}
set_load_weight(&init_task, false);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5130239c0e1e5..6a97ee2a4e26d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5514,6 +5514,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
*/
util_est_enqueue(&rq->cfs, p);
+ if (!rq->cfs.h_nr_running)
+ dl_server_start(&rq->fair_server);
+
/*
* If in_iowait is set, the code below may not trigger any cpufreq
* utilization updates, so do it here explicitly with the IOWAIT flag
@@ -5666,6 +5669,9 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
rq->next_balance = jiffies;
dequeue_throttle:
+ if (!rq->cfs.h_nr_running)
+ dl_server_stop(&rq->fair_server);
+
util_est_dequeue(&rq->cfs, p, task_sleep);
hrtick_update(rq);
}
@@ -7151,6 +7157,29 @@ static struct task_struct *__pick_next_task_fair(struct rq *rq)
return pick_next_task_fair(rq, NULL, NULL);
}
+static bool fair_server_has_tasks(struct sched_dl_entity *dl_se)
+{
+ return !!dl_se->rq->cfs.nr_running;
+}
+
+static struct task_struct *fair_server_pick(struct sched_dl_entity *dl_se)
+{
+ return pick_next_task_fair(dl_se->rq, NULL, NULL);
+}
+
+void fair_server_init(struct rq *rq)
+{
+ struct sched_dl_entity *dl_se = &rq->fair_server;
+
+ init_dl_entity(dl_se);
+
+ dl_se->dl_runtime = TICK_NSEC;
+ dl_se->dl_deadline = 20 * TICK_NSEC;
+ dl_se->dl_period = 20 * TICK_NSEC;
+
+ dl_server_init(dl_se, rq, fair_server_has_tasks, fair_server_pick);
+}
+
/*
* Account for a descheduled task:
*/
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index f035cd8ccd224..bf8c9c07705c9 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -375,6 +375,8 @@ extern void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
dl_server_has_tasks_f has_tasks,
dl_server_pick_f pick);
+extern void fair_server_init(struct rq *);
+
#ifdef CONFIG_CGROUP_SCHED
#include <linux/cgroup.h>
@@ -959,6 +961,8 @@ struct rq {
struct rt_rq rt;
struct dl_rq dl;
+ struct sched_dl_entity fair_server;
+
#ifdef CONFIG_FAIR_GROUP_SCHED
/* list of leaf cfs_rq on this CPU: */
struct list_head leaf_cfs_rq_list;
--
2.26.2
next prev parent reply other threads:[~2020-08-07 9:51 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-07 9:50 [RFC PATCH v2 0/6] SCHED_DEADLINE server infrastructure Juri Lelli
2020-08-07 9:50 ` [RFC PATCH v2 1/6] sched: Unify runtime accounting across classes Juri Lelli
2020-08-07 9:50 ` [RFC PATCH v2 2/6] sched/deadline: Collect sched_dl_entity initialization Juri Lelli
2020-08-07 9:50 ` [RFC PATCH v2 3/6] sched/deadline: Move bandwidth accounting into {en,de}queue_dl_entity Juri Lelli
2020-08-07 9:50 ` [RFC PATCH v2 4/6] sched/deadline: Introduce deadline servers Juri Lelli
2020-10-06 7:56 ` luca abeni
2020-10-06 9:35 ` Juri Lelli
2020-10-06 9:51 ` luca abeni
2020-08-07 9:50 ` Juri Lelli [this message]
2020-08-07 9:56 ` [RFC PATCH v2 6/6] sched/fair: Implement starvation monitor Juri Lelli
2020-08-07 10:46 ` peterz
2020-08-07 11:30 ` Daniel Bristot de Oliveira
2020-08-07 12:50 ` Juri Lelli
2020-08-07 13:49 ` luca abeni
2020-08-07 14:11 ` peterz
2020-08-07 16:48 ` Daniel Bristot de Oliveira
2020-08-07 13:28 ` luca abeni
2020-08-07 13:43 ` Juri Lelli
2020-08-07 13:55 ` luca abeni
2020-08-07 14:11 ` Juri Lelli
2020-08-07 14:13 ` peterz
2020-08-07 15:06 ` Juri Lelli
2020-08-07 13:16 ` [RFC PATCH v2 0/6] SCHED_DEADLINE server infrastructure luca abeni
2020-08-07 13:30 ` Juri Lelli
2020-08-07 13:41 ` luca abeni
2020-08-07 14:04 ` Juri Lelli
2020-08-07 14:14 ` peterz
2020-09-08 22:22 ` Pavel Machek
2020-09-09 5:51 ` Juri Lelli
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