diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2026-03-10 20:02:21 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@kernel.org> | 2026-03-11 21:13:55 +0100 |
| commit | 92f7ee408c23fcc074e4952fb6ffacdf3eb86b56 (patch) | |
| tree | 018695d125b282ea9f8bbcb2de5f575c395472f2 /kernel/time | |
| parent | eef9f648fb0e92618041f019d4bdcf7ae17cb743 (diff) | |
hrtimer: Less agressive interrupt 'hang' handling
When the hrtimer_interrupt needs to restart more than 3 times and still has
expired timers, the interrupt is considered hung. To give the system a
little time to recover, the hardware timer is programmed a little into the
future.
Prior to commit 288924384856 ("hrtimer: Re-arrange hrtimer_interrupt()"),
this was relative to the amount of time spend serving the interrupt with a
max of 100 msec.
However, in order to simplify, and because this condition 'should' not
happen, the timeout was unconditionally set to 100 msec.
'Obviously' there is a benchmark that hits this hard, by programming a
ton of very short timers :-/
Since reprogramming is decoupled from the interrupt handling, the actual
execution time is lost, however the code does track max_hang_time. Using
that, rather than the 100 ms max restores performance.
stress-ng --timeout 60 --times --verify --metrics --no-rand-seed --timermix 64
bogo ops/s
288924384856^1: 23715979.93
288924384856: 11550049.77
patched: 23361116.78
Additionally, Thomas noted that cpu_base->hang_detected should not be
cleared until the next interrupt, such that __hrtimer_reprogram() won't
undo the extra delay.
Fixes: 288924384856 ("hrtimer: Re-arrange hrtimer_interrupt()")
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260311121500.GF652779@noisy.programming.kicks-ass.net
Closes: https://lore.kernel.org/oe-lkp/202603102229.74b9dee4-lkp@intel.com
Diffstat (limited to 'kernel/time')
| -rw-r--r-- | kernel/time/hrtimer.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index b94bd56b739f..cafd6771a225 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -2031,8 +2031,8 @@ static void hrtimer_rearm(struct hrtimer_cpu_base *cpu_base, ktime_t expires_nex * Give the system a chance to do something else than looping * on hrtimer interrupts. */ - expires_next = ktime_add_ns(ktime_get(), 100 * NSEC_PER_MSEC); - cpu_base->hang_detected = false; + expires_next = ktime_add_ns(ktime_get(), + min(100 * NSEC_PER_MSEC, cpu_base->max_hang_time)); } hrtimer_rearm_event(expires_next, deferred); } @@ -2121,6 +2121,7 @@ retry: */ now = hrtimer_update_base(cpu_base); expires_next = hrtimer_update_next_event(cpu_base); + cpu_base->hang_detected = false; if (expires_next < now) { if (++retries < 3) goto retry; |