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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
This commit is contained in:
Thomas Gleixner 2012-05-25 22:08:58 +00:00
parent facbb4a7ef
commit 99d5f3aac6
1 changed files with 23 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
kernel/timer.c
View File

@ -77,6 +77,7 @@ struct tvec_base {
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 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
__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 @@ static inline void detach_timer(struct timer_list *timer, bool clear_pending)
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 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
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 @@ static inline void __run_timers(struct tvec_base *base)
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 @@ static int __cpuinit init_timers_cpu(int cpu)
base->timer_jiffies = jiffies;
base->next_timer = base->timer_jiffies;
base->active_timers = 0;
return 0;
}
@ -1711,6 +1725,7 @@ static void migrate_timer_list(struct tvec_base *new_base, struct list_head *hea
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);