hrtimer: Eliminate needless reprogramming of clock events device
On NOHZ systems the following timers, - tick_nohz_restart_sched_tick (tick_sched_timer) - hrtimer_start (tick_sched_timer) are reprogramming the clock events device far more often than needed. No specific test case was required to observe this effect. This occurres because there was no check to see if the currently removed or restarted hrtimer was: 1) the one which previously armed the clock events device. 2) going to be replaced by another timer which has the same expiry time. Avoid the reprogramming in hrtimer_force_reprogram when the new expiry value which is evaluated from the clock bases is equal to cpu_base->expires_next. This results in faster application startup time by ~4%. [ tglx: simplified initial solution ] Signed-off-by: NAshwin Chaugule <ashwinc@quicinc.com> LKML-Reference: <4AA00165.90609@codeaurora.org> Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
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