From: Yunfeng Ye yeyunfeng@huawei.com
mainline inclusion from mainline-5.14-rc1 commit a5183862e76fdc25f36b39c2489b816a5c66e2e5 category: feature feature: Deep isolation bugzilla: https://gitee.com/openeuler/kernel/issues/I4N00D CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
--------------------------------
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 Reviewed-by: Chao Liu liuchao173@huawei.com Reviewed-by: Chen Hui judy.chenhui@huawei.com Acked-by: Xie XiuQi xiexiuqi@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- kernel/time/tick-sched.c | 42 ++++++++++++++++++++++++++-------------- 1 file changed, 27 insertions(+), 15 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 651545679c3e..eea50baf9cb0 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -906,22 +906,28 @@ 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) @@ -1185,18 +1191,24 @@ 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) +void tick_nohz_idle_restart_tick(void) { - tick_nohz_restart_sched_tick(ts, now); - tick_nohz_account_idle_ticks(ts); + struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + + if (ts->tick_stopped) { + tick_nohz_restart_sched_tick(ts, ktime_get()); + tick_nohz_account_idle_ticks(ts); + } }
-void tick_nohz_idle_restart_tick(void) +static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now) { - struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); + if (tick_nohz_full_cpu(smp_processor_id())) + __tick_nohz_full_update_tick(ts, now); + else + tick_nohz_restart_sched_tick(ts, now);
- if (ts->tick_stopped) - __tick_nohz_idle_restart_tick(ts, ktime_get()); + tick_nohz_account_idle_ticks(ts); }
/** @@ -1228,7 +1240,7 @@ 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(); }