On Wed, Oct 23, 2013 at 02:58:05PM +0200, Stephane Eranian wrote:
> The RAPL PMU counters do not interrupt on overflow.
> Therefore, the kernel needs to poll the counters
> to avoid missing an overflow. This patch adds
> the hrtimer code to do this.
>
> The timer internval is calculated at boot time
> based on the power unit used by the HW.
>
> Signed-off-by: Stephane Eranian <eran...@google.com>
> ---
> arch/x86/kernel/cpu/perf_event_intel_rapl.c | 75
> +++++++++++++++++++++++++--
> 1 file changed, 70 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> index 3d71d39..ed0566a 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> +++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
> @@ -92,11 +92,13 @@ static struct kobj_attribute format_attr_##_var =
> \
>
> struct rapl_pmu {
> spinlock_t lock;
> - atomic_t refcnt;
> int hw_unit; /* 1/2^hw_unit Joule */
> - int phys_id;
> - int n_active; /* number of active events */
> + struct hrtimer hrtimer;
> struct list_head active_list;
> + ktime_t timer_interval; /* in ktime_t unit */
> + int n_active; /* number of active events */
> + int phys_id;
> + atomic_t refcnt;
> };
>
> static struct pmu rapl_pmu_class;
> @@ -161,6 +163,47 @@ static u64 rapl_event_update(struct perf_event *event)
> return new_raw_count;
> }
>
> +static void rapl_start_hrtimer(struct rapl_pmu *pmu)
> +{
> + __hrtimer_start_range_ns(&pmu->hrtimer,
> + pmu->timer_interval, 0,
> + HRTIMER_MODE_REL_PINNED, 0);
> +}
> +
> +static void rapl_stop_hrtimer(struct rapl_pmu *pmu)
> +{
> + hrtimer_cancel(&pmu->hrtimer);
> +}
> +
> +static enum hrtimer_restart rapl_hrtimer_handle(struct hrtimer *hrtimer)
> +{
> + struct rapl_pmu *pmu = container_of(hrtimer, struct rapl_pmu, hrtimer);
> + struct perf_event *event;
> + unsigned long flags;
> +
> + if (!pmu->n_active)
> + return HRTIMER_NORESTART;
> +
> + spin_lock_irqsave(&pmu->lock, flags);
> +
> + list_for_each_entry(event, &pmu->active_list, active_entry) {
> + rapl_event_update(event);
> + }
hi,
I dont fully understand the reason for the timer,
I'm probably missing something..
- the timer calls rapl_event_update for all defined events
- but rapl_pmu_event_read calls rapl_event_update any time the
event is read (sys_read)
The rapl_event_update only read msr and updates
event->count|hw,prev_count.
What's the timer purpose then?
thanks for info,
jirka
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