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authorFrederic Weisbecker <frederic@kernel.org>2020-07-17 16:05:45 +0200
committerThomas Gleixner <tglx@linutronix.de>2020-07-17 21:55:22 +0200
commit001ec1b3925da0d51847c23fc0aa4129282db526 (patch)
tree0ca510af92153bc4788f719e657e3532eed825dd /kernel/time
parent4468897211628865ee2392acb5ad281f74176f63 (diff)
timers: Optimize _next_timer_interrupt() level iteration
If a level has a timer that expires before reaching the next level, there is no need to iterate further. The next level is reached when the 3 lower bits of the current level are cleared. If the next event happens before/during that, the next levels won't provide an earlier expiration. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lkml.kernel.org/r/20200717140551.29076-7-frederic@kernel.org
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/timer.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index af1c08b0b168..9abc41715fd2 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1526,6 +1526,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base)
clk = base->clk;
for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
+ unsigned long lvl_clk = clk & LVL_CLK_MASK;
if (pos >= 0) {
unsigned long tmp = clk + (unsigned long) pos;
@@ -1533,6 +1534,13 @@ static unsigned long __next_timer_interrupt(struct timer_base *base)
tmp <<= LVL_SHIFT(lvl);
if (time_before(tmp, next))
next = tmp;
+
+ /*
+ * If the next expiration happens before we reach
+ * the next level, no need to check further.
+ */
+ if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
+ break;
}
/*
* Clock for the next level. If the current level clock lower
@@ -1570,7 +1578,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base)
* So the simple check whether the lower bits of the current
* level are 0 or not is sufficient for all cases.
*/
- adj = clk & LVL_CLK_MASK ? 1 : 0;
+ adj = lvl_clk ? 1 : 0;
clk >>= LVL_CLK_SHIFT;
clk += adj;
}