On Thu, 16 Mar 2017, tip-bot for Alexander Shishkin wrote:
> Commit-ID: ae0c2d995d648d5165545d5e05e2869642009b38
> perf/core: Add a flag for partial AUX records
>
> The Intel PT driver needs to be able to communicate partial AUX transactions,
> that is, transactions with gaps in data for reasons other than no room
> left in the buffer (i.e. truncated transactions). Therefore, this condition
> does not imply a wakeup for the consumer.
>
> To this end, add a new "partial" AUX flag.
...
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index bec0aad..d09a9cd 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -915,6 +915,7 @@ enum perf_callchain_context {
> */
> #define PERF_AUX_FLAG_TRUNCATED 0x01 /* record was truncated to fit */
> #define PERF_AUX_FLAG_OVERWRITE 0x02 /* snapshot from overwrite mode */
> +#define PERF_AUX_FLAG_PARTIAL 0x04 /* record contains gaps */
was this included in the wrong patch? It adds the flag but nothing uses
it? Though it appears a later patch makes use of it.
This makes it confusing when trying to update the perf_event_open.2
manpage, as the git commit that adds the new ABI to perf_event.h doesn't
seem to have anything to do with any behavior affected by it.
> #define PERF_FLAG_FD_NO_GROUP (1UL << 0)
> #define PERF_FLAG_FD_OUTPUT (1UL << 1)
> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
> index 9654e55..2831480 100644
> --- a/kernel/events/ring_buffer.c
> +++ b/kernel/events/ring_buffer.c
> @@ -424,8 +424,8 @@ err:
> */
> void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
> {
> + bool wakeup = !!(handle->aux_flags & PERF_AUX_FLAG_TRUNCATED);
> struct ring_buffer *rb = handle->rb;
> - bool wakeup = !!handle->aux_flags;
> unsigned long aux_head;
>
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