lkml.org 
[lkml]   [2018]   [May]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 3/6] arm_pmu: Add support for long event counters
From
Date
On 18/05/18 11:22, Suzuki K Poulose wrote:
> Each PMU has a set of fixed width event counters. But in some
> special cases, the events could be counted using a counter which
> effectively has twice the normal width of a coutner.
> e.g, Arm V8 PMUv3 has a 64 bit cycle counter which can count
> only the CPU cylces. Also, the PMU can chain the event counters
> to effectively count as a 64bit counter.

Nit: a few typos in that paragraph.

> Add support for tracking the events that uses double the normal
> counter size. This only affects the periods set for each counter.
>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> drivers/perf/arm_pmu.c | 25 ++++++++++++++++++++++---
> include/linux/perf/arm_pmu.h | 6 ++++++
> 2 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
> index e23e1a1..1adabb5 100644
> --- a/drivers/perf/arm_pmu.c
> +++ b/drivers/perf/arm_pmu.c
> @@ -33,6 +33,21 @@ static inline u64 arm_pmu_max_period(struct arm_pmu *pmu)
> return (((u64)1) << (pmu->counter_width)) - 1;
> }
>
> +static inline u64 arm_pmu_get_event_max_period(struct arm_pmu *pmu,

The "get_" here seems a bit at odds with arm_pmu_max_period() - I'd be
inlined to go for slightly more consistent naming (with a slight
personal preference towards removing it here rather than adding it there)

> + struct perf_event *event)
> +{
> + u64 period = arm_pmu_max_period(pmu);
> +
> + /*
> + * To prevent shift-counter-overflow warning, create the
> + * mask, by shift + OR sequence.
> + */
> + if (event->hw.flags & ARMPMU_EVT_LONG)
> + period = (period << pmu->counter_width) | period;
> +
> + return period;
> +}
> +
> static int
> armpmu_map_cache_event(const unsigned (*cache_map)
> [PERF_COUNT_HW_CACHE_MAX]
> @@ -122,7 +137,7 @@ int armpmu_event_set_period(struct perf_event *event)
> u64 max_period;
> int ret = 0;
>
> - max_period = arm_pmu_max_period(armpmu);
> + max_period = arm_pmu_get_event_max_period(armpmu, event);
> if (unlikely(left <= -period)) {
> left = period;
> local64_set(&hwc->period_left, left);
> @@ -148,7 +163,7 @@ int armpmu_event_set_period(struct perf_event *event)
>
> local64_set(&hwc->prev_count, (u64)-left);
>
> - armpmu->write_counter(event, (u64)(-left) & 0xffffffff);
> + armpmu->write_counter(event, (u64)(-left) & max_period);
>
> perf_event_update_userpage(event);
>
> @@ -160,7 +175,7 @@ u64 armpmu_event_update(struct perf_event *event)
> struct arm_pmu *armpmu = to_arm_pmu(event->pmu);
> struct hw_perf_event *hwc = &event->hw;
> u64 delta, prev_raw_count, new_raw_count;
> - u64 max_period = arm_pmu_max_period(armpmu);
> + u64 max_period = arm_pmu_get_event_max_period(armpmu, event);
>
> again:
> prev_raw_count = local64_read(&hwc->prev_count);
> @@ -368,6 +383,7 @@ __hw_perf_event_init(struct perf_event *event)
> struct hw_perf_event *hwc = &event->hw;
> int mapping;
>
> + hwc->flags = 0;
> mapping = armpmu->map_event(event);
>
> if (mapping < 0) {
> @@ -670,6 +686,9 @@ static void cpu_pm_pmu_setup(struct arm_pmu *armpmu, unsigned long cmd)
> continue;
>
> event = hw_events->events[idx];
> + /* Chained events could use multiple counters */
> + if (!event)
> + continue;

This hunk looks a little out of place; does it perhaps belong to patch #6?

Robin.

>
> switch (cmd) {
> case CPU_PM_ENTER:
> diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
> index 705e8c3..ed7e3f7 100644
> --- a/include/linux/perf/arm_pmu.h
> +++ b/include/linux/perf/arm_pmu.h
> @@ -25,6 +25,12 @@
> */
> #define ARMPMU_MAX_HWEVENTS 32
>
> +/*
> + * ARM PMU hw_event flags
> + */
> +/* Event uses a counter with double the normal width */
> +#define ARMPMU_EVT_LONG 1
> +
> #define HW_OP_UNSUPPORTED 0xFFFF
> #define C(_x) PERF_COUNT_HW_CACHE_##_x
> #define CACHE_OP_UNSUPPORTED 0xFFFF
>

\
 
 \ /
  Last update: 2018-05-18 15:23    [W:0.130 / U:0.712 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site