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Message-Id: <e4519f6850477ab7f3d257062796e6425ee4ba7c.1559129225.git.vpillai@digitalocean.com>
Date: Wed, 29 May 2019 20:36:43 +0000
From: Vineeth Remanan Pillai <vpillai@...italocean.com>
To: Nishanth Aravamudan <naravamudan@...italocean.com>,
Julien Desfossez <jdesfossez@...italocean.com>,
Peter Zijlstra <peterz@...radead.org>,
Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org
Cc: linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
Aubrey Li <aubrey.intel@...il.com>,
Valentin Schneider <valentin.schneider@....com>,
Mel Gorman <mgorman@...hsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>
Subject: [RFC PATCH v3 07/16] sched: Allow put_prev_task() to drop rq->lock
From: Peter Zijlstra <peterz@...radead.org>
Currently the pick_next_task() loop is convoluted and ugly because of
how it can drop the rq->lock and needs to restart the picking.
For the RT/Deadline classes, it is put_prev_task() where we do
balancing, and we could do this before the picking loop. Make this
possible.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
kernel/sched/core.c | 2 +-
kernel/sched/deadline.c | 14 +++++++++++++-
kernel/sched/fair.c | 2 +-
kernel/sched/idle.c | 2 +-
kernel/sched/rt.c | 14 +++++++++++++-
kernel/sched/sched.h | 4 ++--
kernel/sched/stop_task.c | 2 +-
7 files changed, 32 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 32ea79fb8d29..9dfa0c53deb3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5595,7 +5595,7 @@ static void calc_load_migrate(struct rq *rq)
atomic_long_add(delta, &calc_load_tasks);
}
-static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
+static void put_prev_task_fake(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
}
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c02b3229e2c3..45425f971eec 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1772,13 +1772,25 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
return p;
}
-static void put_prev_task_dl(struct rq *rq, struct task_struct *p)
+static void put_prev_task_dl(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
{
update_curr_dl(rq);
update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 1);
if (on_dl_rq(&p->dl) && p->nr_cpus_allowed > 1)
enqueue_pushable_dl_task(rq, p);
+
+ if (rf && !on_dl_rq(&p->dl) && need_pull_dl_task(rq, p)) {
+ /*
+ * This is OK, because current is on_cpu, which avoids it being
+ * picked for load-balance and preemption/IRQs are still
+ * disabled avoiding further scheduler activity on it and we've
+ * not yet started the picking loop.
+ */
+ rq_unpin_lock(rq, rf);
+ pull_dl_task(rq);
+ rq_repin_lock(rq, rf);
+ }
}
/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 49707b4797de..8e3eb243fd9f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7110,7 +7110,7 @@ done: __maybe_unused;
/*
* Account for a descheduled task:
*/
-static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
+static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
struct sched_entity *se = &prev->se;
struct cfs_rq *cfs_rq;
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index dd64be34881d..1b65a4c3683e 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -373,7 +373,7 @@ static void check_preempt_curr_idle(struct rq *rq, struct task_struct *p, int fl
resched_curr(rq);
}
-static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
+static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
}
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index adec98a94f2b..51ee87c5a28a 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1593,7 +1593,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
return p;
}
-static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
+static void put_prev_task_rt(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
{
update_curr_rt(rq);
@@ -1605,6 +1605,18 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
*/
if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1)
enqueue_pushable_task(rq, p);
+
+ if (rf && !on_rt_rq(&p->rt) && need_pull_rt_task(rq, p)) {
+ /*
+ * This is OK, because current is on_cpu, which avoids it being
+ * picked for load-balance and preemption/IRQs are still
+ * disabled avoiding further scheduler activity on it and we've
+ * not yet started the picking loop.
+ */
+ rq_unpin_lock(rq, rf);
+ pull_rt_task(rq);
+ rq_repin_lock(rq, rf);
+ }
}
#ifdef CONFIG_SMP
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index bfcbcbb25646..4cbe2bef92e4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1675,7 +1675,7 @@ struct sched_class {
struct task_struct * (*pick_next_task)(struct rq *rq,
struct task_struct *prev,
struct rq_flags *rf);
- void (*put_prev_task)(struct rq *rq, struct task_struct *p);
+ void (*put_prev_task)(struct rq *rq, struct task_struct *p, struct rq_flags *rf);
void (*set_next_task)(struct rq *rq, struct task_struct *p);
#ifdef CONFIG_SMP
@@ -1721,7 +1721,7 @@ struct sched_class {
static inline void put_prev_task(struct rq *rq, struct task_struct *prev)
{
WARN_ON_ONCE(rq->curr != prev);
- prev->sched_class->put_prev_task(rq, prev);
+ prev->sched_class->put_prev_task(rq, prev, NULL);
}
static inline void set_next_task(struct rq *rq, struct task_struct *next)
diff --git a/kernel/sched/stop_task.c b/kernel/sched/stop_task.c
index 47a3d2a18a9a..8f414018d5e0 100644
--- a/kernel/sched/stop_task.c
+++ b/kernel/sched/stop_task.c
@@ -59,7 +59,7 @@ static void yield_task_stop(struct rq *rq)
BUG(); /* the stop task should never yield, its pointless. */
}
-static void put_prev_task_stop(struct rq *rq, struct task_struct *prev)
+static void put_prev_task_stop(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
{
struct task_struct *curr = rq->curr;
u64 delta_exec;
--
2.17.1
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