The following commit has been merged into the timers/core branch of tip:
Commit-ID: d4f7dae87096dfe722bf32aa82076ece1063746c
Gitweb: https://git.kernel.org/tip/d4f7dae87096dfe722bf32aa82076ece1063746c
Author: Frederic Weisbecker <frederic@xxxxxxxxxx>
AuthorDate: Fri, 17 Jul 2020 16:05:49 +02:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Fri, 17 Jul 2020 21:55:24 +02:00
timers: Spare timer softirq until next expiry
Now that the core timer infrastructure doesn't depend anymore on
periodic base->clk increments, even when the CPU is not in NO_HZ mode,
timer softirqs can be skipped until there are timers to expire.
Some spurious softirqs can still remain since base->next_expiry doesn't
keep track of canceled timers but this still reduces the number of softirqs
significantly: ~15 times less for HZ=1000 and ~5 times less for HZ=100.
Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200717140551.29076-11-frederic@xxxxxxxxxx
---
kernel/time/timer.c | 49 +++++++-------------------------------------
1 file changed, 8 insertions(+), 41 deletions(-)
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1be92b5..4f78a7b 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1458,10 +1458,10 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head)
}
}
-static int __collect_expired_timers(struct timer_base *base,
- struct hlist_head *heads)
+static int collect_expired_timers(struct timer_base *base,
+ struct hlist_head *heads)
{
- unsigned long clk = base->clk;
+ unsigned long clk = base->clk = base->next_expiry;
struct hlist_head *vec;
int i, levels = 0;
unsigned int idx;
@@ -1684,40 +1684,6 @@ void timer_clear_idle(void)
*/
base->is_idle = false;
}
-
-static int collect_expired_timers(struct timer_base *base,
- struct hlist_head *heads)
-{
- unsigned long now = READ_ONCE(jiffies);
-
- /*
- * NOHZ optimization. After a long idle sleep we need to forward the
- * base to current jiffies. Avoid a loop by searching the bitfield for
- * the next expiring timer.
- */
- if ((long)(now - base->clk) > 2) {
- /*
- * If the next timer is ahead of time forward to current
- * jiffies, otherwise forward to the next expiry time:
- */
- if (time_after(base->next_expiry, now)) {
- /*
- * The call site will increment base->clk and then
- * terminate the expiry loop immediately.
- */
- base->clk = now;
- return 0;
- }
- base->clk = base->next_expiry;
- }
- return __collect_expired_timers(base, heads);
-}
-#else
-static inline int collect_expired_timers(struct timer_base *base,
- struct hlist_head *heads)
-{
- return __collect_expired_timers(base, heads);
-}
#endif
/*
@@ -1750,7 +1716,7 @@ static inline void __run_timers(struct timer_base *base)
struct hlist_head heads[LVL_DEPTH];
int levels;
- if (!time_after_eq(jiffies, base->clk))
+ if (time_before(jiffies, base->next_expiry))
return;
timer_base_lock_expiry(base);
@@ -1763,7 +1729,8 @@ static inline void __run_timers(struct timer_base *base)
*/
base->must_forward_clk = false;
- while (time_after_eq(jiffies, base->clk)) {
+ while (time_after_eq(jiffies, base->clk) &&
+ time_after_eq(jiffies, base->next_expiry)) {
levels = collect_expired_timers(base, heads);
base->clk++;
@@ -1798,12 +1765,12 @@ void run_local_timers(void)
hrtimer_run_queues();
/* Raise the softirq only if required. */
- if (time_before(jiffies, base->clk)) {
+ if (time_before(jiffies, base->next_expiry)) {
if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
return;
/* CPU is awake, so check the deferrable base. */
base++;
- if (time_before(jiffies, base->clk))
+ if (time_before(jiffies, base->next_expiry))
return;
}
raise_softirq(TIMER_SOFTIRQ);
|