timers: Add accounting of non deferrable timers
The code in get_next_timer_interrupt() is suboptimal as it has to run
through the cascade to find the next expiring timer. On a completely
idle core we should only do that when there is an active timer
enqueued and base->next_timer does not give us a fast answer.
Add accounting of the active timers to the now consolidated
attach/detach code. I deliberately avoided sanity checks because the
code is fully symetric and any fiddling with timers w/o using the API
functions will lead to cute explosions anyway. ulong is big enough
even on 32bit and if we really run into the situation to have more
than 1<<32 timers enqueued there, then we are definitely not in a
state to go idle and run through that code.
This allows us to fix another shortcoming of get_next_timer_interrupt().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/20120525214819.236377028@linutronix.de
diff --git a/kernel/timer.c b/kernel/timer.c
index 7207690..7fada69 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -77,6 +77,7 @@
struct timer_list *running_timer;
unsigned long timer_jiffies;
unsigned long next_timer;
+ unsigned long active_timers;
struct tvec_root tv1;
struct tvec tv2;
struct tvec tv3;
@@ -377,11 +378,13 @@
{
__internal_add_timer(base, timer);
/*
- * Update base->next_timer if this is the earliest one.
+ * Update base->active_timers and base->next_timer
*/
- if (time_before(timer->expires, base->next_timer) &&
- !tbase_get_deferrable(timer->base))
- base->next_timer = timer->expires;
+ if (!tbase_get_deferrable(timer->base)) {
+ if (time_before(timer->expires, base->next_timer))
+ base->next_timer = timer->expires;
+ base->active_timers++;
+ }
}
#ifdef CONFIG_TIMER_STATS
@@ -678,6 +681,14 @@
entry->prev = LIST_POISON2;
}
+static inline void
+detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
+{
+ detach_timer(timer, true);
+ if (!tbase_get_deferrable(timer->base))
+ timer->base->active_timers--;
+}
+
static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
bool clear_pending)
{
@@ -685,9 +696,11 @@
return 0;
detach_timer(timer, clear_pending);
- if (timer->expires == base->next_timer &&
- !tbase_get_deferrable(timer->base))
- base->next_timer = base->timer_jiffies;
+ if (!tbase_get_deferrable(timer->base)) {
+ timer->base->active_timers--;
+ if (timer->expires == base->next_timer)
+ base->next_timer = base->timer_jiffies;
+ }
return 1;
}
@@ -1175,7 +1188,7 @@
timer_stats_account_timer(timer);
base->running_timer = timer;
- detach_timer(timer, true);
+ detach_expired_timer(timer, base);
spin_unlock_irq(&base->lock);
call_timer_fn(timer, fn, data);
@@ -1701,6 +1714,7 @@
base->timer_jiffies = jiffies;
base->next_timer = base->timer_jiffies;
+ base->active_timers = 0;
return 0;
}
@@ -1711,6 +1725,7 @@
while (!list_empty(head)) {
timer = list_first_entry(head, struct timer_list, entry);
+ /* We ignore the accounting on the dying cpu */
detach_timer(timer, false);
timer_set_base(timer, new_base);
internal_add_timer(new_base, timer);
