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SubjectRe: [RFC 02/11] perf/core: Data structure to present hazard data
On Mon, Mar 02, 2020 at 10:53:46AM +0530, Ravi Bangoria wrote:
> From: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
>
> Introduce new perf sample_type PERF_SAMPLE_PIPELINE_HAZ to request kernel
> to provide cpu pipeline hazard data. Also, introduce arch independent
> structure 'perf_pipeline_haz_data' to pass hazard data to userspace. This
> is generic structure and arch specific data needs to be converted to this
> format.
>
> Signed-off-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
> ---
> include/linux/perf_event.h | 7 ++++++
> include/uapi/linux/perf_event.h | 32 ++++++++++++++++++++++++++-
> kernel/events/core.c | 6 +++++
> tools/include/uapi/linux/perf_event.h | 32 ++++++++++++++++++++++++++-
> 4 files changed, 75 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index 547773f5894e..d5b606e3c57d 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -1001,6 +1001,7 @@ struct perf_sample_data {
> u64 stack_user_size;
>
> u64 phys_addr;
> + struct perf_pipeline_haz_data pipeline_haz;
> } ____cacheline_aligned;
>
> /* default value for data source */
> @@ -1021,6 +1022,12 @@ static inline void perf_sample_data_init(struct perf_sample_data *data,
> data->weight = 0;
> data->data_src.val = PERF_MEM_NA;
> data->txn = 0;
> + data->pipeline_haz.itype = PERF_HAZ__ITYPE_NA;
> + data->pipeline_haz.icache = PERF_HAZ__ICACHE_NA;
> + data->pipeline_haz.hazard_stage = PERF_HAZ__PIPE_STAGE_NA;
> + data->pipeline_haz.hazard_reason = PERF_HAZ__HREASON_NA;
> + data->pipeline_haz.stall_stage = PERF_HAZ__PIPE_STAGE_NA;
> + data->pipeline_haz.stall_reason = PERF_HAZ__SREASON_NA;
> }
>
> extern void perf_output_sample(struct perf_output_handle *handle,
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 377d794d3105..ff252618ca93 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -142,8 +142,9 @@ enum perf_event_sample_format {
> PERF_SAMPLE_REGS_INTR = 1U << 18,
> PERF_SAMPLE_PHYS_ADDR = 1U << 19,
> PERF_SAMPLE_AUX = 1U << 20,
> + PERF_SAMPLE_PIPELINE_HAZ = 1U << 21,

Can we please have perf_event_open() reject this sample flag for PMUs
without the new callback (introduced in the next patch)?

That way it'll be possible to detect whether the PMU exposes this.

Thanks,
Mark.

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