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

Ian Rogers
2022-11-14T07:52:12Z

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. */
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;
};

--
2.38.1.431.g37b22c650d-goog