[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>

1 files changed, 12 insertions, 8 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 6401c31d6add..64e2754ca734 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -72,14 +72,16 @@ struct hrtimer {
 /**
  * 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 hrtimer_base {
         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;
 };
 
 /*