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

[Mark Rutland <mark.rutland@arm.com>]

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;

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
>