Re: [PATCH v1 1/9] perf pmu: Add documentation

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2022-11-14 2:51 a.m., Ian Rogers wrote:
> Add documentation to struct perf_pmu and the associated structs of
> perf_pmu_alias and perf_pmu_format.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/pmu.c |  14 ++++++
>  tools/perf/util/pmu.h | 105 +++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 113 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
> index 6a86e6af0903..a8f9f47c6ed9 100644
> --- a/tools/perf/util/pmu.c
> +++ b/tools/perf/util/pmu.c
> @@ -31,10 +31,24 @@
>  
>  struct perf_pmu perf_pmu__fake;
>  
> +/**
> + * Values from a format file read from <sysfs>/devices/cpu/format/ held in
> + * struct perf_pmu. For example, the contents of
> + * <sysfs>/devices/cpu/format/event may be "config:0-7" and will be represented
> + * here as name="event", value=PERF_PMU_FORMAT_VALUE_CONFIG and bits 0 to 7 will
> + * be set.
> + */
>  struct perf_pmu_format {
> +	/** The modifier/file name. */
>  	char *name;
> +	/**
> +	 * Which config value the format relates to. Supported values are from
> +	 * PERF_PMU_FORMAT_VALUE_CONFIG to PERF_PMU_FORMAT_VALUE_CONFIG_END.
> +	 */
>  	int value;
> +	/** Which config bits are set by this format value. */
>  	DECLARE_BITMAP(bits, PERF_PMU_FORMAT_BITS);
> +	/** Element on list within struct perf_pmu. */
>  	struct list_head list;
>  };
>  
> diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
> index 68e15c38ae71..29571c0f9d15 100644
> --- a/tools/perf/util/pmu.h
> +++ b/tools/perf/util/pmu.h
> @@ -34,30 +34,91 @@ struct perf_pmu_caps {
>  };
>  
>  struct perf_pmu {
> +	/** The name of the PMU such as "cpu". */
>  	char *name;
> +	/**
> +	 * Optional alternate name for the PMU determined in architecture
> +	 * specific code.
> +	 */
>  	char *alias_name;
> +	/**
> +	 * Optional PMU identifier read from
> +	 * <sysfs>/bus/event_source/devices/<name>/identifier.
> +	 */
>  	char *id;
> +	/**
> +	 * Perf event attributed type value, read from
> +	 * <sysfs>/bus/event_source/devices/<name>/type.
> +	 */
>  	__u32 type;
> +	/**
> +	 * Can the PMU name be selected as if it were an event?
> +	 */
>  	bool selectable;
> +	/**
> +	 * Is the PMU not within the CPU core? Determined by the presence of
> +	 * <sysfs>/bus/event_source/devices/<name>/cpumask.
> +	 */
>  	bool is_uncore;
> +	/** Is the PMU name either cpu_core or cpu_atom. */

I don't think we want to limit the hybrid names only to cpu_core or
cpu_atom. Maybe something as below?
/* Is a hybrid CPU PMU, e.g., cpu_core, cpu_atom. */

Thanks,
Kan

>  	bool is_hybrid;
> +	/**
> +	 * Are events auxiliary events? Determined in architecture specific
> +	 * code.
> +	 */
>  	bool auxtrace;
> +	/**
> +	 * Number of levels of :ppp precision supported by the PMU, read from
> +	 * <sysfs>/bus/event_source/devices/<name>/caps/max_precise.
> +	 */
>  	int max_precise;
> +	/**
> +	 * Optional default perf_event_attr determined in architecture specific
> +	 * code.
> +	 */
>  	struct perf_event_attr *default_config;
> +	/**
> +	 * Empty or the contents of either of:
> +	 * <sysfs>/bus/event_source/devices/<name>/cpumask.
> +	 * <sysfs>/bus/event_source/devices/<cpu>/cpus.
> +	 */
>  	struct perf_cpu_map *cpus;
> -	struct list_head format;  /* HEAD struct perf_pmu_format -> list */
> -	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
> +	/**
> +	 * Holds the contents of files read from
> +	 * <sysfs>/bus/event_source/devices/<name>/format/. The contents specify
> +	 * which event parameter changes what config, config1 or config2 bits.
> +	 */
> +	struct list_head format;
> +	/**
> +	 * List of struct perf_pmu_alias. Each alias corresponds to an event
> +	 * read from <sysfs>/bus/event_source/devices/<name>/events/ or from
> +	 * json events in pmu-events.c.
> +	 */
> +	struct list_head aliases;
> +	/** Has the list caps been initialized? */
>  	bool caps_initialized;
> +	/** The length of the list caps. */
>  	u32 nr_caps;
> -	struct list_head caps;    /* HEAD struct perf_pmu_caps -> list */
> -	struct list_head list;    /* ELEM */
> +	/**
> +	 * Holds the contents of files read from
> +	 * <sysfs>/bus/event_source/devices/<name>/caps/. The contents are pairs
> +	 * of the filename with the value of its contents, for example,
> +	 * max_precise (see above) may have a value of 3.
> +	 */
> +	struct list_head caps;
> +	/** Element on pmus list in pmu.c. */
> +	struct list_head list;
> +	/** Element on perf_pmu__hybrid_pmus. */
>  	struct list_head hybrid_list;
>  
> +	/** Features to inhibit when events on this PMU are opened. */
>  	struct {
> +		/** Disables perf_event_attr exclude_guest and exclude_host. */
>  		bool exclude_guest;
>  	} missing_features;
>  };
>  
> +/** A special global PMU used for testing. */
>  extern struct perf_pmu perf_pmu__fake;
>  
>  struct perf_pmu_info {
> @@ -71,21 +132,53 @@ struct perf_pmu_info {
>  
>  #define UNIT_MAX_LEN	31 /* max length for event unit name */
>  
> +/**
> + * An event either read from sysfs or builtin in pmu-events.c, created by
> + * parsing the pmu-events json files.
> + */
>  struct perf_pmu_alias {
>  	char *name;
> +	/** Optional short description of the event. */
>  	char *desc;
> +	/** Optional long description. */
>  	char *long_desc;
> +	/**
> +	 * Optional topic such as cache or pipeline, particularly for json
> +	 * events.
> +	 */
>  	char *topic;
> +	/** Comma separated parameter list. */
>  	char *str;
> -	struct list_head terms; /* HEAD struct parse_events_term -> list */
> -	struct list_head list;  /* ELEM */
> +	/** Owned list of the original parsed parameters. */
> +	struct list_head terms;
> +	/** List element of struct perf_pmu aliases. */
> +	struct list_head list;
> +	/** Units for the event, such as bytes or cache lines. */
>  	char unit[UNIT_MAX_LEN+1];
> +	/** Value to scale read counter values by. */
>  	double scale;
> +	/**
> +	 * Does the file
> +	 * <sysfs>/bus/event_source/devices/<pmu_name>/events/<name>.per-pkg or
> +	 * equivalent json value exist and have the value 1.
> +	 */
>  	bool per_pkg;
> +	/**
> +	 * Does the file
> +	 * <sysfs>/bus/event_source/devices/<pmu_name>/events/<name>.snapshot
> +	 * exist and have the value 1.
> +	 */
>  	bool snapshot;
> +	/** Is the event hidden and so not shown in perf list by default. */
>  	bool deprecated;
> +	/**
> +	 * A metric expression associated with an event. Doing this makes little
> +	 * sense due to scale and unit applying to both.
> +	 */
>  	char *metric_expr;
> +	/** A name for the metric. unit applying to both. */
>  	char *metric_name;
> +	/** The name copied from struct perf_pmu. */
>  	char *pmu_name;
>  };
>