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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-07-28 23:39:25 +0200 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-09-08 01:27:27 +0200 |
| commit | c7b24d2b9a0f2ce19fdf631d3148c80a8f6010b1 (patch) | |
| tree | 0845fff0ca580e0394746e6545b9f038bc4b8a44 /kernel/rcu/update.c | |
| parent | rcu: Add stall-warning checks for RCU-tasks (diff) | |
| download | linux-c7b24d2b9a0f2ce19fdf631d3148c80a8f6010b1.tar.xz linux-c7b24d2b9a0f2ce19fdf631d3148c80a8f6010b1.zip | |
rcu: Improve RCU-tasks energy efficiency
The current RCU-tasks implementation uses strict polling to detect
callback arrivals. This works quite well, but is not so good for
energy efficiency. This commit therefore replaces the strict polling
with a wait queue.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/update.c')
| -rw-r--r-- | kernel/rcu/update.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index bad7dbd4c2e3..444c8a303963 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -365,6 +365,7 @@ early_initcall(check_cpu_stall_init); /* Global list of callbacks and associated lock. */ static struct rcu_head *rcu_tasks_cbs_head; static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head; +static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq); static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); /* Track exiting tasks in order to allow them to be waited for. */ @@ -378,13 +379,17 @@ module_param(rcu_task_stall_timeout, int, 0644); void call_rcu_tasks(struct rcu_head *rhp, void (*func)(struct rcu_head *rhp)) { unsigned long flags; + bool needwake; rhp->next = NULL; rhp->func = func; raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags); + needwake = !rcu_tasks_cbs_head; *rcu_tasks_cbs_tail = rhp; rcu_tasks_cbs_tail = &rhp->next; raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags); + if (needwake) + wake_up(&rcu_tasks_cbs_wq); } EXPORT_SYMBOL_GPL(call_rcu_tasks); @@ -495,8 +500,12 @@ static int __noreturn rcu_tasks_kthread(void *arg) /* If there were none, wait a bit and start over. */ if (!list) { - schedule_timeout_interruptible(HZ); - WARN_ON(signal_pending(current)); + wait_event_interruptible(rcu_tasks_cbs_wq, + rcu_tasks_cbs_head); + if (!rcu_tasks_cbs_head) { + WARN_ON(signal_pending(current)); + schedule_timeout_interruptible(HZ/10); + } continue; } @@ -602,6 +611,7 @@ static int __noreturn rcu_tasks_kthread(void *arg) list = next; cond_resched(); } + schedule_timeout_uninterruptible(HZ/10); } } |