Re: [PATCH] hrtimer: Replace cpu_base->active_bases with a direct check of the active list

On Thu, 9 Apr 2015, Ingo Molnar wrote:

Plus, look at this code in hrtimer_run_queues():

    for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
            base = &cpu_base->clock_base[index];
            if (!base->active.next)
                    continue;

            if (gettime) {
                    hrtimer_get_softirq_time(cpu_base);
                    gettime = 0;
            }

if at least one base is active (on my fairly standard system all cpus have at least one active hrtimer base all the time - and many cpus have two bases active), then we run hrtimer_get_softirq_time(), which dirties the cachelines of all 4 clock bases:

    base->clock_base[HRTIMER_BASE_REALTIME].softirq_time = xtim;
    base->clock_base[HRTIMER_BASE_MONOTONIC].softirq_time = mono;
    base->clock_base[HRTIMER_BASE_BOOTTIME].softirq_time = boot;
    base->clock_base[HRTIMER_BASE_TAI].softirq_time = tai;

This is the non highres case and we actually could optimize that case as well to avoid the cache line polution.

Thanks,

tglx