Re: [RFC 02/11] perf/core: Data structure to present hazard data

From: Mark Rutland
Date: Mon Mar 02 2020 - 09:54:42 EST

On Mon, Mar 02, 2020 at 10:53:46AM +0530, Ravi Bangoria wrote:
> From: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
> ---
> 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;

I don't think you can add this here, see below.

> /* 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,
>
> - PERF_SAMPLE_MAX = 1U << 21, /* non-ABI */
> + PERF_SAMPLE_MAX = 1U << 22, /* non-ABI */
>
> __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /* non-ABI; internal use */
> };
> @@ -870,6 +871,13 @@ enum perf_event_type {
> * { u64 phys_addr;} && PERF_SAMPLE_PHYS_ADDR
> * { u64 size;
> * char data[size]; } && PERF_SAMPLE_AUX
> + * { u8 itype;
> + * u8 icache;
> + * u8 hazard_stage;
> + * u8 hazard_reason;
> + * u8 stall_stage;
> + * u8 stall_reason;
> + * u16 pad;} && PERF_SAMPLE_PIPELINE_HAZ
> * };

The existing comment shows the aux data *immediately* after ther
phys_addr field, where you've placed struct perf_pipeline_haz_data.

If adding to struct perf_sample_data is fine, this needs to come before
the aux data in this comment. If adding to struct perf_sample_data is
not fine. struct perf_pipeline_haz_data cannot live there.

I suspect the latter is true, but you're getting away with it because
you're not using both PERF_SAMPLE_AUX and PERF_SAMPLE_PIPELINE_HAZ
simultaneously.

Thanks,
Mark.

> */
> PERF_RECORD_SAMPLE = 9,
> @@ -1185,4 +1193,26 @@ struct perf_branch_entry {
> reserved:40;
> };
>
> +struct perf_pipeline_haz_data {
> + /* Instruction/Opcode type: Load, Store, Branch .... */
> + __u8 itype;
> + /* Instruction Cache source */
> + __u8 icache;
> + /* Instruction suffered hazard in pipeline stage */
> + __u8 hazard_stage;
> + /* Hazard reason */
> + __u8 hazard_reason;
> + /* Instruction suffered stall in pipeline stage */
> + __u8 stall_stage;
> + /* Stall reason */
> + __u8 stall_reason;
> + __u16 pad;
> +};
> +
> +#define PERF_HAZ__ITYPE_NA 0x0
> +#define PERF_HAZ__ICACHE_NA 0x0
> +#define PERF_HAZ__PIPE_STAGE_NA 0x0
> +#define PERF_HAZ__HREASON_NA 0x0
> +#define PERF_HAZ__SREASON_NA 0x0
> +
> #endif /* _UAPI_LINUX_PERF_EVENT_H */
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index e453589da97c..d00037c77ccf 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -1754,6 +1754,9 @@ static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
> if (sample_type & PERF_SAMPLE_PHYS_ADDR)
> size += sizeof(data->phys_addr);
>
> + if (sample_type & PERF_SAMPLE_PIPELINE_HAZ)
> + size += sizeof(data->pipeline_haz);
> +
> event->header_size = size;
> }
>
> @@ -6712,6 +6715,9 @@ void perf_output_sample(struct perf_output_handle *handle,
> perf_aux_sample_output(event, handle, data);
> }
>
> + if (sample_type & PERF_SAMPLE_PIPELINE_HAZ)
> + perf_output_put(handle, data->pipeline_haz);
> +
> if (!event->attr.watermark) {
> int wakeup_events = event->attr.wakeup_events;
>
> diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
> index 377d794d3105..ff252618ca93 100644
> --- a/tools/include/uapi/linux/perf_event.h
> +++ b/tools/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,
>
> - PERF_SAMPLE_MAX = 1U << 21, /* non-ABI */
> + PERF_SAMPLE_MAX = 1U << 22, /* non-ABI */
>
> __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63, /* non-ABI; internal use */
> };
> @@ -870,6 +871,13 @@ enum perf_event_type {
> * { u64 phys_addr;} && PERF_SAMPLE_PHYS_ADDR
> * { u64 size;
> * char data[size]; } && PERF_SAMPLE_AUX
> + * { u8 itype;
> + * u8 icache;
> + * u8 hazard_stage;
> + * u8 hazard_reason;
> + * u8 stall_stage;
> + * u8 stall_reason;
> + * u16 pad;} && PERF_SAMPLE_PIPELINE_HAZ
> * };
> */
> PERF_RECORD_SAMPLE = 9,
> @@ -1185,4 +1193,26 @@ struct perf_branch_entry {
> reserved:40;
> };
>
> +struct perf_pipeline_haz_data {
> + /* Instruction/Opcode type: Load, Store, Branch .... */
> + __u8 itype;
> + /* Instruction Cache source */
> + __u8 icache;
> + /* Instruction suffered hazard in pipeline stage */
> + __u8 hazard_stage;
> + /* Hazard reason */
> + __u8 hazard_reason;
> + /* Instruction suffered stall in pipeline stage */
> + __u8 stall_stage;
> + /* Stall reason */
> + __u8 stall_reason;
> + __u16 pad;
> +};
> +
> +#define PERF_HAZ__ITYPE_NA 0x0
> +#define PERF_HAZ__ICACHE_NA 0x0
> +#define PERF_HAZ__PIPE_STAGE_NA 0x0
> +#define PERF_HAZ__HREASON_NA 0x0
> +#define PERF_HAZ__SREASON_NA 0x0
> +
> #endif /* _UAPI_LINUX_PERF_EVENT_H */
> --
> 2.21.1
>