[PATCH] hrtimers: optimize softirq runqueues
The hrtimer softirq is called from the timer softirq every tick. Retrieve the
current time from xtime and wall_to_monotonic instead of calling
base->get_time() for each timer base. Store the time in the base structure
and provide a hook once clock source abstractions are in place and to keep the
code open for new base clocks.
Based on a patch from: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 6401c31..64e2754 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -72,14 +72,16 @@
/**
* struct hrtimer_base - the timer base for a specific clock
*
- * @index: clock type index for per_cpu support when moving a timer
- * to a base on another cpu.
- * @lock: lock protecting the base and associated timers
- * @active: red black tree root node for the active timers
- * @first: pointer to the timer node which expires first
- * @resolution: the resolution of the clock, in nanoseconds
- * @get_time: function to retrieve the current time of the clock
- * @curr_timer: the timer which is executing a callback right now
+ * @index: clock type index for per_cpu support when moving a timer
+ * to a base on another cpu.
+ * @lock: lock protecting the base and associated timers
+ * @active: red black tree root node for the active timers
+ * @first: pointer to the timer node which expires first
+ * @resolution: the resolution of the clock, in nanoseconds
+ * @get_time: function to retrieve the current time of the clock
+ * @get_sofirq_time: function to retrieve the current time from the softirq
+ * @curr_timer: the timer which is executing a callback right now
+ * @softirq_time: the time when running the hrtimer queue in the softirq
*/
struct hrtimer_base {
clockid_t index;
@@ -88,7 +90,9 @@
struct rb_node *first;
ktime_t resolution;
ktime_t (*get_time)(void);
+ ktime_t (*get_softirq_time)(void);
struct hrtimer *curr_timer;
+ ktime_t softirq_time;
};
/*
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 14bc9cf..b728cc5 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -123,6 +123,26 @@
EXPORT_SYMBOL_GPL(ktime_get_ts);
/*
+ * Get the coarse grained time at the softirq based on xtime and
+ * wall_to_monotonic.
+ */
+static void hrtimer_get_softirq_time(struct hrtimer_base *base)
+{
+ ktime_t xtim, tomono;
+ unsigned long seq;
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+ xtim = timespec_to_ktime(xtime);
+ tomono = timespec_to_ktime(wall_to_monotonic);
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ base[CLOCK_REALTIME].softirq_time = xtim;
+ base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
+}
+
+/*
* Functions and macros which are different for UP/SMP systems are kept in a
* single place
*/
@@ -586,9 +606,11 @@
*/
static inline void run_hrtimer_queue(struct hrtimer_base *base)
{
- ktime_t now = base->get_time();
struct rb_node *node;
+ if (base->get_softirq_time)
+ base->softirq_time = base->get_softirq_time();
+
spin_lock_irq(&base->lock);
while ((node = base->first)) {
@@ -598,7 +620,7 @@
void *data;
timer = rb_entry(node, struct hrtimer, node);
- if (now.tv64 <= timer->expires.tv64)
+ if (base->softirq_time.tv64 <= timer->expires.tv64)
break;
fn = timer->function;
@@ -641,6 +663,8 @@
struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
int i;
+ hrtimer_get_softirq_time(base);
+
for (i = 0; i < MAX_HRTIMER_BASES; i++)
run_hrtimer_queue(&base[i]);
}
