Messages in this thread Patch in this message | | | From | Levi Yun <> | Subject | [PATCH v4] time/tick-sched: idle load balancing when nohz_full cpu becomes idle. | Date | Thu, 9 May 2024 10:29:32 +0100 |
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When nohz_full CPU stops tick in tick_nohz_irq_exit(), It wouldn't be chosen to perform idle load balancing because it doesn't call nohz_balance_enter_idle() in tick_nohz_idle_stop_tick() when it becomes idle.
Formerly, __tick_nohz_idle_enter() is called in both tick_nohz_irq_exit() and in do_idle(). That's why commit a0db971e4eb6 ("nohz: Move idle balancer registration to the idle path") prevents nohz_full cpu which isn't yet idle state but tick is stopped from entering idle balance.
However, this prevents nohz_full cpu which already stops tick from entering idle balacne when this cpu really becomes idle state.
Currently, tick_nohz_idle_stop_tick() is only called in idle state and it calls nohz_balance_enter_idle(). this function tracks the CPU which is part of nohz.idle_cpus_mask with rq->nohz_tick_stopped properly.
Therefore, Change tick_nohz_idle_stop_tick() to call nohz_balance_enter_idle() without checking !was_stopped so that nohz_full cpu can be chosen to perform idle load balancing when it enters idle state.
Fixes: a0db971e4eb6 ("nohz: Move idle balancer registration to the idle path") Signed-off-by: Levi Yun <ppbuk5246@gmail.com> --- v4: - Add fixes tags.
v3: - Rewording commit message.
v2: - Fix typos in commit message.
kernel/time/tick-sched.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 71a792cd8936..31a4cd89782f 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -1228,8 +1228,10 @@ void tick_nohz_idle_stop_tick(void) ts->idle_sleeps++; ts->idle_expires = expires;
- if (!was_stopped && tick_sched_flag_test(ts, TS_FLAG_STOPPED)) { - ts->idle_jiffies = ts->last_jiffies; + if (tick_sched_flag_test(ts, TS_FLAG_STOPPED)) { + if (!was_stopped) + ts->idle_jiffies = ts->last_jiffies; + nohz_balance_enter_idle(cpu); } } else { -- 2.41.0
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