nohz: Allow to check if remote CPU tick is stopped
This check is racy but provides a good heuristic to determine whether a CPU may need a remote tick or not. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Link: http://lkml.kernel.org/r/1519186649-3242-4-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -114,6 +114,7 @@ enum tick_dep_bits {
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#ifdef CONFIG_NO_HZ_COMMON
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extern bool tick_nohz_enabled;
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extern bool tick_nohz_tick_stopped(void);
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extern bool tick_nohz_tick_stopped_cpu(int cpu);
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extern void tick_nohz_idle_enter(void);
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extern void tick_nohz_idle_exit(void);
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extern void tick_nohz_irq_exit(void);
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@ -125,6 +126,7 @@ extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
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#else /* !CONFIG_NO_HZ_COMMON */
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#define tick_nohz_enabled (0)
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static inline int tick_nohz_tick_stopped(void) { return 0; }
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static inline int tick_nohz_tick_stopped_cpu(int cpu) { return 0; }
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static inline void tick_nohz_idle_enter(void) { }
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static inline void tick_nohz_idle_exit(void) { }
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@ -486,6 +486,13 @@ bool tick_nohz_tick_stopped(void)
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return __this_cpu_read(tick_cpu_sched.tick_stopped);
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}
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bool tick_nohz_tick_stopped_cpu(int cpu)
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{
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struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
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return ts->tick_stopped;
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}
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/**
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* tick_nohz_update_jiffies - update jiffies when idle was interrupted
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*
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