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[PATCH] hrtimers: optimize softirq runqueues

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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>
This commit is contained in:
Thomas Gleixner 2006-03-26 01:38:05 -08:00 committed by Linus Torvalds
parent a0e9285233
commit 92127c7a45
2 changed files with 38 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
include/linux/hrtimer.h
View file

@ -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;
};
/*

28
kernel/hrtimer.c
View file

@ -122,6 +122,26 @@ void ktime_get_ts(struct timespec *ts)
}
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 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
*/
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 @@ static inline void run_hrtimer_queue(struct hrtimer_base *base)
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 @@ void hrtimer_run_queues(void)
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]);
}