On Wed, Nov 23, 2016 at 04:44:39AM -0500, [email protected] wrote:
> From: Kan Liang <[email protected]>
>
> A new perf record is introduced to export perf overhead information to
> userspace. So we can measure the overhead of sampling directly.
>
> To output the overhead information, it takes advantage of the existing
> event log mechanism. But the overhead information is the system
> overhead, not per-event overhead.
>
> Signed-off-by: Kan Liang <[email protected]>
> ---
> include/linux/perf_event.h | 4 ++++
> include/uapi/linux/perf_event.h | 29 +++++++++++++++++++++++++++
> kernel/events/core.c | 43
> +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 76 insertions(+)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 4741ecd..3a530a7 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -998,6 +998,10 @@ perf_event__output_id_sample(struct perf_event *event,
> extern void
> perf_log_lost_samples(struct perf_event *event, u64 lost);
>
> +extern void
> +perf_log_overhead(struct perf_event *event, u32 type,
> + struct perf_overhead_entry *entry);
> +
> static inline bool is_sampling_event(struct perf_event *event)
> {
> return event->attr.sample_period != 0;
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index c66a485..ae571be 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -862,6 +862,17 @@ enum perf_event_type {
> */
> PERF_RECORD_SWITCH_CPU_WIDE = 15,
>
> + /*
> + * Records perf overhead
> + * struct {
> + * struct perf_event_header header;
> + * u32 type;
> + * struct perf_overhead_entry entry;
> + * struct sample_id sample_id;
> + * };
> + */
> + PERF_RECORD_OVERHEAD = 16,
> +
> PERF_RECORD_MAX, /* non-ABI */
> };
I think we should make this optional/configurable like the
rest of the aux events, like below..
jirka
---
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 5e7c52278ef0..853a919bd9ae 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -344,7 +344,8 @@ struct perf_event_attr {
use_clockid : 1, /* use @clockid for time
fields */
context_switch : 1, /* context switch data */
write_backward : 1, /* Write ring buffer from
end to beginning */
- __reserved_1 : 36;
+ overhead : 1,
+ __reserved_1 : 35;
union {
__u32 wakeup_events; /* wakeup every n events */
