Messages in this thread | | | Date | Wed, 12 Sep 2012 17:37:18 +0200 | Subject | Re: [PATCH v2 2/3] perf: use hrtimer for event multiplexing | From | Stephane Eranian <> |
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On Wed, Sep 12, 2012 at 4:43 PM, Stephane Eranian <eranian@google.com> wrote: > On Wed, Sep 12, 2012 at 4:22 PM, Peter Zijlstra <peterz@infradead.org> wrote: >> On Wed, 2012-09-12 at 16:13 +0200, Stephane Eranian wrote: >>> +static DEFINE_PER_CPU(struct list_head, rotation_list); >> >> Why do you keep the rotation list? The only use seems to be: >> >> >>> +void perf_cpu_hrtimer_cancel(int cpu) >>> +{ >>> + struct list_head *head = &__get_cpu_var(rotation_list); >>> + struct perf_cpu_context *cpuctx, *tmp; >>> + unsigned long flags; >>> + >>> + if (WARN_ON(cpu != smp_processor_id())) >>> + return; >>> + >>> + local_irq_save(flags); >>> + >>> + list_for_each_entry_safe(cpuctx, tmp, head, rotation_list) { >>> + if (cpuctx->hrtimer_active) { >>> + hrtimer_cancel(&cpuctx->hrtimer); >>> + cpuctx->hrtimer_active = 0; >>> + } >>> + } >>> + >>> + local_irq_restore(flags); >>> +} >> >> Which is weird, why not use the existing for-each-pmu loop in >> perf_event_exit_cpu_context() ? Or something similar to iterate all >> extant PMUs and thus their cpuctxs? >> > True. That would probably work too. > Note however that the rotation_list is still used in perf_event_task_tick() to iterate over the ctx which needs unthrottling. We would have to switch that loop over to a for-each-pmu() which would necessary incur more iterations as it would include all the SW PMUs.
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