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tick/nohz: Conditionally restart tick on idle exit 

In nohz_full mode, switching from idle to a task will unconditionally
issue a tick restart. If the task is alone in the runqueue or is the
highest priority, the tick will fire once then eventually stop. But that
alone is still undesired noise.

Therefore, only restart the tick on idle exit when it's strictly
necessary.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-3-frederic@kernel.org
This commit is contained in:
Yunfeng Ye 2021-05-13 01:29:16 +02:00 committed by Ingo Molnar
parent f105dfec0a
commit a5183862e7
1 changed files with 28 additions and 16 deletions
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44
kernel/time/tick-sched.c
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@ -926,22 +926,28 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
tick_nohz_restart(ts, now);
}
static void tick_nohz_full_update_tick(struct tick_sched *ts)
static void __tick_nohz_full_update_tick(struct tick_sched *ts,
ktime_t now)
{
#ifdef CONFIG_NO_HZ_FULL
int cpu = smp_processor_id();
if (!tick_nohz_full_cpu(cpu))
if (can_stop_full_tick(cpu, ts))
tick_nohz_stop_sched_tick(ts, cpu);
else if (ts->tick_stopped)
tick_nohz_restart_sched_tick(ts, now);
#endif
}
static void tick_nohz_full_update_tick(struct tick_sched *ts)
{
if (!tick_nohz_full_cpu(smp_processor_id()))
return;
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
return;
if (can_stop_full_tick(cpu, ts))
tick_nohz_stop_sched_tick(ts, cpu);
else if (ts->tick_stopped)
tick_nohz_restart_sched_tick(ts, ktime_get());
#endif
__tick_nohz_full_update_tick(ts, ktime_get());
}
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
@ -1209,18 +1215,24 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
#endif
}
static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now)
{
tick_nohz_restart_sched_tick(ts, now);
tick_nohz_account_idle_ticks(ts);
}
void tick_nohz_idle_restart_tick(void)
{
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
if (ts->tick_stopped)
__tick_nohz_idle_restart_tick(ts, ktime_get());
if (ts->tick_stopped) {
tick_nohz_restart_sched_tick(ts, ktime_get());
tick_nohz_account_idle_ticks(ts);
}
}
static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
{
if (tick_nohz_full_cpu(smp_processor_id()))
__tick_nohz_full_update_tick(ts, now);
else
tick_nohz_restart_sched_tick(ts, now);
tick_nohz_account_idle_ticks(ts);
}
/**
@ -1252,7 +1264,7 @@ void tick_nohz_idle_exit(void)
tick_nohz_stop_idle(ts, now);
if (tick_stopped)
__tick_nohz_idle_restart_tick(ts, now);
tick_nohz_idle_update_tick(ts, now);
local_irq_enable();
}