The following commit has been merged into the timers/core branch of tip: Commit-ID: 001ec1b3925da0d51847c23fc0aa4129282db526 Gitweb: https://git.kernel.org/tip/001ec1b3925da0d51847c23fc0aa4129282db526 Author: Frederic Weisbecker <[email protected]> AuthorDate: Fri, 17 Jul 2020 16:05:45 +02:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Fri, 17 Jul 2020 21:55:22 +02:00
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 <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Juri Lelli <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- kernel/time/timer.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/kernel/time/timer.c b/kernel/time/timer.c index af1c08b..9abc417 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; }
