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| author | Peter Zijlstra <peterz@infradead.org> | 2020-12-10 17:14:08 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2020-12-15 11:27:53 +0100 |
| commit | ae7927023243dcc7389b2d59b16c09cbbeaecc36 (patch) | |
| tree | 64bdf7a8cddcc7a2c2631a107dee1b5bbc4e7405 /kernel/sched/sched.h | |
| parent | 5b78f2dc315354c05300795064f587366a02c6ff (diff) | |
| download | linux-ae7927023243dcc7389b2d59b16c09cbbeaecc36.tar.gz linux-ae7927023243dcc7389b2d59b16c09cbbeaecc36.tar.bz2 linux-ae7927023243dcc7389b2d59b16c09cbbeaecc36.zip | |
sched: Optimize finish_lock_switch()
The kernel test robot measured a -1.6% performance regression on
will-it-scale/sched_yield due to commit:
2558aacff858 ("sched/hotplug: Ensure only per-cpu kthreads run during hotplug")
Even though we were careful to replace a single load with another
single load from the same cacheline.
Restore finish_lock_switch() to the exact state before the offending
patch and solve the problem differently.
Fixes: 2558aacff858 ("sched/hotplug: Ensure only per-cpu kthreads run during hotplug")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201210161408.GX3021@hirez.programming.kicks-ass.net
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 13 |
1 files changed, 5 insertions, 8 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f5acb6c5ce49..12ada79d40f3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -975,7 +975,6 @@ struct rq { unsigned long cpu_capacity_orig; struct callback_head *balance_callback; - unsigned char balance_flags; unsigned char nohz_idle_balance; unsigned char idle_balance; @@ -1226,6 +1225,8 @@ struct rq_flags { #endif }; +extern struct callback_head balance_push_callback; + /* * Lockdep annotation that avoids accidental unlocks; it's like a * sticky/continuous lockdep_assert_held(). @@ -1243,9 +1244,9 @@ static inline void rq_pin_lock(struct rq *rq, struct rq_flags *rf) #ifdef CONFIG_SCHED_DEBUG rq->clock_update_flags &= (RQCF_REQ_SKIP|RQCF_ACT_SKIP); rf->clock_update_flags = 0; -#endif #ifdef CONFIG_SMP - SCHED_WARN_ON(rq->balance_callback); + SCHED_WARN_ON(rq->balance_callback && rq->balance_callback != &balance_push_callback); +#endif #endif } @@ -1408,9 +1409,6 @@ init_numa_balancing(unsigned long clone_flags, struct task_struct *p) #ifdef CONFIG_SMP -#define BALANCE_WORK 0x01 -#define BALANCE_PUSH 0x02 - static inline void queue_balance_callback(struct rq *rq, struct callback_head *head, @@ -1418,13 +1416,12 @@ queue_balance_callback(struct rq *rq, { lockdep_assert_held(&rq->lock); - if (unlikely(head->next || (rq->balance_flags & BALANCE_PUSH))) + if (unlikely(head->next || rq->balance_callback == &balance_push_callback)) return; head->func = (void (*)(struct callback_head *))func; head->next = rq->balance_callback; rq->balance_callback = head; - rq->balance_flags |= BALANCE_WORK; } #define rcu_dereference_check_sched_domain(p) \ |