On Fri, Jul 08, 2016 at 03:31:00PM +0200, Peter Zijlstra wrote:
SNIP
> /*
> - * When the event is constrained enough we can use a larger
> - * threshold and run the event with less frequent PMI.
> + * Use auto-reload if possible to save a MSR write in the PMI.
> + * This must be done in pmu::start(), because PERF_EVENT_IOC_PERIOD.
> */
> - if (hwc->flags & PERF_X86_EVENT_FREERUNNING) {
> - threshold = ds->pebs_absolute_maximum -
> - x86_pmu.max_pebs_events * x86_pmu.pebs_record_size;
> -
> - if (first_pebs)
> - perf_sched_cb_inc(event->ctx->pmu);
> - } else {
> - threshold = ds->pebs_buffer_base + x86_pmu.pebs_record_size;
> -
> - /*
> - * If not all events can use larger buffer,
> - * roll back to threshold = 1
> - */
> - if (!first_pebs &&
> - (ds->pebs_interrupt_threshold > threshold))
> - perf_sched_cb_dec(event->ctx->pmu);
> - }
hum, the original code switched back the perf_sched_cb,
in case !feerunning event was detected.. I dont see it
in the new code.. just the threshold update
jirka
