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Message-ID: <162081530619.29796.11256820252103924811.tip-bot2@tip-bot2>
Date: Wed, 12 May 2021 10:28:26 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Peter Zijlstra (Intel)" <peterz@...radead.org>,
Don Hiatt <dhiatt@...italocean.com>,
Hongyu Ning <hongyu.ning@...ux.intel.com>,
Vincent Guittot <vincent.guittot@...aro.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched: Optimize rq_lockp() usage
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 9ef7e7e33bcdb57be1afb28884053c28b5f05240
Gitweb: https://git.kernel.org/tip/9ef7e7e33bcdb57be1afb28884053c28b5f05240
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Wed, 03 Mar 2021 16:45:41 +01:00
Committer: Peter Zijlstra <peterz@...radead.org>
CommitterDate: Wed, 12 May 2021 11:43:27 +02:00
sched: Optimize rq_lockp() usage
rq_lockp() includes a static_branch(), which is asm-goto, which is
asm volatile which defeats regular CSE. This means that:
if (!static_branch(&foo))
return simple;
if (static_branch(&foo) && cond)
return complex;
Doesn't fold and we get horrible code. Introduce __rq_lockp() without
the static_branch() on.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Don Hiatt <dhiatt@...italocean.com>
Tested-by: Hongyu Ning <hongyu.ning@...ux.intel.com>
Tested-by: Vincent Guittot <vincent.guittot@...aro.org>
Link: https://lkml.kernel.org/r/20210422123308.316696988@infradead.org
---
kernel/sched/core.c | 16 ++++++++--------
kernel/sched/deadline.c | 4 ++--
kernel/sched/fair.c | 2 +-
kernel/sched/sched.h | 33 +++++++++++++++++++++++++--------
4 files changed, 36 insertions(+), 19 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 384b793..42c1c88 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -300,9 +300,9 @@ void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
}
for (;;) {
- lock = rq_lockp(rq);
+ lock = __rq_lockp(rq);
raw_spin_lock_nested(lock, subclass);
- if (likely(lock == rq_lockp(rq))) {
+ if (likely(lock == __rq_lockp(rq))) {
/* preempt_count *MUST* be > 1 */
preempt_enable_no_resched();
return;
@@ -325,9 +325,9 @@ bool raw_spin_rq_trylock(struct rq *rq)
}
for (;;) {
- lock = rq_lockp(rq);
+ lock = __rq_lockp(rq);
ret = raw_spin_trylock(lock);
- if (!ret || (likely(lock == rq_lockp(rq)))) {
+ if (!ret || (likely(lock == __rq_lockp(rq)))) {
preempt_enable();
return ret;
}
@@ -352,7 +352,7 @@ void double_rq_lock(struct rq *rq1, struct rq *rq2)
swap(rq1, rq2);
raw_spin_rq_lock(rq1);
- if (rq_lockp(rq1) == rq_lockp(rq2))
+ if (__rq_lockp(rq1) == __rq_lockp(rq2))
return;
raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
@@ -2622,7 +2622,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
* task_rq_lock().
*/
WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
- lockdep_is_held(rq_lockp(task_rq(p)))));
+ lockdep_is_held(__rq_lockp(task_rq(p)))));
#endif
/*
* Clearly, migrating tasks to offline CPUs is a fairly daft thing.
@@ -4248,7 +4248,7 @@ prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf
* do an early lockdep release here:
*/
rq_unpin_lock(rq, rf);
- spin_release(&rq_lockp(rq)->dep_map, _THIS_IP_);
+ spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_);
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq_lockp(rq)->owner = next;
@@ -4262,7 +4262,7 @@ static inline void finish_lock_switch(struct rq *rq)
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
- spin_acquire(&rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
+ spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
__balance_callbacks(rq);
raw_spin_rq_unlock_irq(rq);
}
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 6e99b8b..fb0eb9a 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1097,9 +1097,9 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
* If the runqueue is no longer available, migrate the
* task elsewhere. This necessarily changes rq.
*/
- lockdep_unpin_lock(rq_lockp(rq), rf.cookie);
+ lockdep_unpin_lock(__rq_lockp(rq), rf.cookie);
rq = dl_task_offline_migration(rq, p);
- rf.cookie = lockdep_pin_lock(rq_lockp(rq));
+ rf.cookie = lockdep_pin_lock(__rq_lockp(rq));
update_rq_clock(rq);
/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e50bd75..18960d0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1107,7 +1107,7 @@ struct numa_group {
static struct numa_group *deref_task_numa_group(struct task_struct *p)
{
return rcu_dereference_check(p->numa_group, p == current ||
- (lockdep_is_held(rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
+ (lockdep_is_held(__rq_lockp(task_rq(p))) && !READ_ONCE(p->on_cpu)));
}
static struct numa_group *deref_curr_numa_group(struct task_struct *p)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 29418b8..ca30af3 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1133,6 +1133,10 @@ static inline bool sched_core_disabled(void)
return !static_branch_unlikely(&__sched_core_enabled);
}
+/*
+ * Be careful with this function; not for general use. The return value isn't
+ * stable unless you actually hold a relevant rq->__lock.
+ */
static inline raw_spinlock_t *rq_lockp(struct rq *rq)
{
if (sched_core_enabled(rq))
@@ -1141,6 +1145,14 @@ static inline raw_spinlock_t *rq_lockp(struct rq *rq)
return &rq->__lock;
}
+static inline raw_spinlock_t *__rq_lockp(struct rq *rq)
+{
+ if (rq->core_enabled)
+ return &rq->core->__lock;
+
+ return &rq->__lock;
+}
+
#else /* !CONFIG_SCHED_CORE */
static inline bool sched_core_enabled(struct rq *rq)
@@ -1158,11 +1170,16 @@ static inline raw_spinlock_t *rq_lockp(struct rq *rq)
return &rq->__lock;
}
+static inline raw_spinlock_t *__rq_lockp(struct rq *rq)
+{
+ return &rq->__lock;
+}
+
#endif /* CONFIG_SCHED_CORE */
static inline void lockdep_assert_rq_held(struct rq *rq)
{
- lockdep_assert_held(rq_lockp(rq));
+ lockdep_assert_held(__rq_lockp(rq));
}
extern void raw_spin_rq_lock_nested(struct rq *rq, int subclass);
@@ -1346,7 +1363,7 @@ extern struct callback_head balance_push_callback;
*/
static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf)
{
- rf->cookie = lockdep_pin_lock(rq_lockp(rq));
+ rf->cookie = lockdep_pin_lock(__rq_lockp(rq));
#ifdef CONFIG_SCHED_DEBUG
rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP);
@@ -1364,12 +1381,12 @@ static inline void rq_unpin_lock(struct rq *rq, struct rq_flags *rf)
rf->clock_update_flags = RQCF_UPDATED;
#endif
- lockdep_unpin_lock(rq_lockp(rq), rf->cookie);
+ lockdep_unpin_lock(__rq_lockp(rq), rf->cookie);
}
static inline void rq_repin_lock(struct rq *rq, struct rq_flags *rf)
{
- lockdep_repin_lock(rq_lockp(rq), rf->cookie);
+ lockdep_repin_lock(__rq_lockp(rq), rf->cookie);
#ifdef CONFIG_SCHED_DEBUG
/*
@@ -2338,7 +2355,7 @@ static inline int _double_lock_balance(struct rq *this_rq, struct rq *busiest)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
- if (rq_lockp(this_rq) == rq_lockp(busiest))
+ if (__rq_lockp(this_rq) == __rq_lockp(busiest))
return 0;
if (likely(raw_spin_rq_trylock(busiest)))
@@ -2370,9 +2387,9 @@ static inline int double_lock_balance(struct rq *this_rq, struct rq *busiest)
static inline void double_unlock_balance(struct rq *this_rq, struct rq *busiest)
__releases(busiest->lock)
{
- if (rq_lockp(this_rq) != rq_lockp(busiest))
+ if (__rq_lockp(this_rq) != __rq_lockp(busiest))
raw_spin_rq_unlock(busiest);
- lock_set_subclass(&rq_lockp(this_rq)->dep_map, 0, _RET_IP_);
+ lock_set_subclass(&__rq_lockp(this_rq)->dep_map, 0, _RET_IP_);
}
static inline void double_lock(spinlock_t *l1, spinlock_t *l2)
@@ -2412,7 +2429,7 @@ static inline void double_rq_unlock(struct rq *rq1, struct rq *rq2)
__releases(rq1->lock)
__releases(rq2->lock)
{
- if (rq_lockp(rq1) != rq_lockp(rq2))
+ if (__rq_lockp(rq1) != __rq_lockp(rq2))
raw_spin_rq_unlock(rq2);
else
__release(rq2->lock);
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