perf sample: Document struct perf_sample

Add kernel-doc for struct perf_sample capturing the somewhat unusual
population of fields and lifetime relationships.

Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 105 insertions, 4 deletions

diff --git a/tools/perf/util/sample.h b/tools/perf/util/sample.h
index 3cce8dd202aa..9febad1c8207 100644
--- a/tools/perf/util/sample.h
+++ b/tools/perf/util/sample.h
@@ -81,47 +81,148 @@ struct simd_flags {
 #define SIMD_OP_FLAGS_PRED_PARTIAL	0x01	/* partial predicate */
 #define SIMD_OP_FLAGS_PRED_EMPTY	0x02	/* empty predicate */
 
+/**
+ * struct perf_sample
+ *
+ * A sample is generally filled in by evlist__parse_sample/evsel__parse_sample
+ * which fills in the variables from a "union perf_event *event" which is data
+ * from a perf ring buffer or perf.data file. The "event" sample is variable in
+ * length as determined by the perf_event_attr (in the evsel) and details within
+ * the sample event itself. A struct perf_sample avoids needing to care about
+ * the variable length nature of the original event.
+ *
+ * To avoid being excessively large parts of the struct perf_sample are pointers
+ * into the original sample event. In general the lifetime of a struct
+ * perf_sample needs to be less than the "union perf_event *event" it was
+ * derived from.
+ *
+ * The struct regs_dump user_regs and intr_regs are lazily allocated again for
+ * size reasons, due to them holding a cache of looked up registers. The
+ * function pair of perf_sample__init and perf_sample__exit correctly initialize
+ * and clean up these values.
+ */
 struct perf_sample {
+	/** @ip: The sample event PERF_SAMPLE_IP value. */
 	u64 ip;
-	u32 pid, tid;
+	/** @pid: The sample event PERF_SAMPLE_TID pid value. */
+	u32 pid;
+	/** @tid: The sample event PERF_SAMPLE_TID tid value. */
+	u32 tid;
+	/** @time: The sample event PERF_SAMPLE_TIME value. */
 	u64 time;
+	/** @addr: The sample event PERF_SAMPLE_ADDR value. */
 	u64 addr;
+	/** @id: The sample event PERF_SAMPLE_ID or PEF_SAMPLE_IDENTIFIER value. */
 	u64 id;
+	/** @stream_id: The sample event PERF_SAMPLE_STREAM_ID value. */
 	u64 stream_id;
+	/** @period: The sample event PERF_SAMPLE_PERIOD value. */
 	u64 period;
+	/** @weight: Data determined by PERF_SAMPLE_WEIGHT or PERF_SAMPLE_WEIGHT_STRUCT. */
 	u64 weight;
+	/** @transaction: The sample event PERF_SAMPLE_TRANSACTION value. */
 	u64 transaction;
+	/** @insn_cnt: Filled in and used by intel-pt. */
 	u64 insn_cnt;
+	/** @cyc_cnt: Filled in and used by intel-pt. */
 	u64 cyc_cnt;
+	/** @cpu: The sample event PERF_SAMPLE_CPU value. */
 	u32 cpu;
+	/**
+	 * @raw_size: The size in bytes of raw data from PERF_SAMPLE_RAW. For
+	 *            alignment reasons this should always be sizeof(u32)
+	 *            followed by a multiple of sizeof(u64).
+	 */
 	u32 raw_size;
+	/** @data_src: The sample event PERF_SAMPLE_DATA_SRC value. */
 	u64 data_src;
+	/** @phys_addr: The sample event PERF_SAMPLE_PHYS_ADDR value. */
 	u64 phys_addr;
+	/** @data_page_size: The sample event PERF_SAMPLE_DATA_PAGE_SIZE value. */
 	u64 data_page_size;
+	/** @code_page_size: The sample event PERF_SAMPLE_CODE_PAGE_SIZE value. */
 	u64 code_page_size;
+	/** @cgroup: The sample event PERF_SAMPLE_CGROUP value. */
 	u64 cgroup;
+	/** @flags: Extra flag data from auxiliary events like intel-pt. */
 	u32 flags;
+	/** @machine_pid: The guest machine pid derived from the sample id. */
 	u32 machine_pid;
+	/** @vcpu: The guest machine vcpu derived from the sample id. */
 	u32 vcpu;
+	/**
+	 * @insn_len: Instruction length from auxiliary events like
+	 *            intel-pt. The instruction itself is held in insn.
+	 */
 	u16 insn_len;
+	/**
+	 * @cpumode: The cpumode from struct perf_event_header misc variable
+	 *           masked with CPUMODE_MASK. Gives user, kernel and hypervisor
+	 *           information.
+	 */
 	u8  cpumode;
+	/** @misc: The entire struct perf_event_header misc variable. */
 	u16 misc;
+	/**
+	 * @ins_lat: Instruction latency information from weight2 in
+	 *           PERF_SAMPLE_WEIGHT_STRUCT or auxiliary events like
+	 *           intel-pt.
+	 */
 	u16 ins_lat;
-	/** @weight3: On x86 holds retire_lat, on powerpc holds p_stage_cyc. */
+	/**
+	 * @weight3: From PERF_SAMPLE_WEIGHT_STRUCT. On x86 holds retire_lat, on
+	 *           powerpc holds p_stage_cyc.
+	 */
 	u16 weight3;
-	bool no_hw_idx;		/* No hw_idx collected in branch_stack */
-	bool deferred_callchain;	/* Has deferred user callchains */
+	/**
+	 * @no_hw_idx: For PERF_SAMPLE_BRANCH_STACK, true when
+	 *             PERF_SAMPLE_BRANCH_HW_INDEX isn't set.
+	 */
+	bool no_hw_idx;
+	/**
+	 * @deferred_callchain: When processing PERF_SAMPLE_CALLCHAIN a deferred
+	 *                      user callchain marker was encountered.
+	 */
+	bool deferred_callchain;
+	/**
+	 * @deferred_cookie: Identifier of the deferred callchain in the later
+	 *                   PERF_RECORD_CALLCHAIN_DEFERRED event.
+	 */
 	u64 deferred_cookie;
+	/** @insn: A copy of the sampled instruction filled in by perf_sample__fetch_insn. */
 	char insn[MAX_INSN];
+	/** @raw_data: Pointer into the original event for PERF_SAMPLE_RAW data. */
 	void *raw_data;
+	/**
+	 * @callchain: Pointer into the original event for PERF_SAMPLE_CALLCHAIN
+	 *             data. For deferred callchains this may be a copy that
+	 *             needs freeing, see sample__merge_deferred_callchain.
+	 */
 	struct ip_callchain *callchain;
+	/** @branch_stack: Pointer into the original event for PERF_SAMPLE_BRANCH_STACK data. */
 	struct branch_stack *branch_stack;
+	/**
+	 * @branch_stack_cntr: Pointer into the original event for
+	 *                     PERF_SAMPLE_BRANCH_COUNTERS data.
+	 */
 	u64 *branch_stack_cntr;
+	/** @user_regs: Values and pointers into the sample for PERF_SAMPLE_REGS_USER. */
 	struct regs_dump  *user_regs;
+	/** @intr_regs: Values and pointers into the sample for PERF_SAMPLE_REGS_INTR. */
 	struct regs_dump  *intr_regs;
+	/** @user_stack: Size and pointer into the sample for PERF_SAMPLE_STACK_USER. */
 	struct stack_dump user_stack;
+	/**
+	 * @read: The sample event PERF_SAMPLE_READ counter values. The valid
+	 *        values depend on the attr.read_format PERF_FORMAT_ values.
+	 */
 	struct sample_read read;
+	/**
+	 * @aux_sample: Similar to raw data but with a 64-bit size and
+	 *              alignment, PERF_SAMPLE_AUX data.
+	 */
 	struct aux_sample aux_sample;
+	/** @simd_flags: SIMD flag information from ARM SPE auxiliary events. */
 	struct simd_flags simd_flags;
 };