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Date: Thu, 22 Apr 2021 14:05:05 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: joel@...lfernandes.org, chris.hyser@...cle.com, joshdon@...gle.com,
mingo@...nel.org, vincent.guittot@...aro.org,
valentin.schneider@....com, mgorman@...e.de
Cc: linux-kernel@...r.kernel.org, peterz@...radead.org,
tglx@...utronix.de
Subject: [PATCH 06/19] 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>
---
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(-)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -281,9 +281,9 @@ void raw_spin_rq_lock_nested(struct rq *
}
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)))
return;
raw_spin_unlock(lock);
}
@@ -298,9 +298,9 @@ bool raw_spin_rq_trylock(struct rq *rq)
return raw_spin_trylock(&rq->__lock);
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))))
return ret;
raw_spin_unlock(lock);
}
@@ -323,7 +323,7 @@ void double_rq_lock(struct rq *rq1, stru
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);
@@ -2594,7 +2594,7 @@ void set_task_cpu(struct task_struct *p,
* 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.
@@ -4220,7 +4220,7 @@ prepare_lock_switch(struct rq *rq, struc
* 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;
@@ -4234,7 +4234,7 @@ static inline void finish_lock_switch(st
* 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);
}
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1097,9 +1097,9 @@ static enum hrtimer_restart dl_task_time
* 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);
/*
--- 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)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1127,6 +1127,10 @@ static inline bool sched_core_disabled(v
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))
@@ -1135,6 +1139,14 @@ static inline raw_spinlock_t *rq_lockp(s
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)
@@ -1152,11 +1164,16 @@ static inline raw_spinlock_t *rq_lockp(s
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);
@@ -1340,7 +1357,7 @@ extern struct callback_head balance_push
*/
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);
@@ -1358,12 +1375,12 @@ static inline void rq_unpin_lock(struct
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
/*
@@ -2306,7 +2323,7 @@ static inline int _double_lock_balance(s
__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)))
@@ -2338,9 +2355,9 @@ static inline int double_lock_balance(st
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)
@@ -2381,7 +2398,7 @@ static inline void double_rq_unlock(stru
__releases(rq2->lock)
{
raw_spin_rq_unlock(rq1);
- 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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