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Date:   Fri, 15 Oct 2021 10:21:21 -0700
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Subject: [PATCH v2 10/21] perf metric: Comment data structures.
From:   Ian Rogers <irogers@google.com>
To:     Andi Kleen <ak@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>,
        Jin Yao <yao.jin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        John Garry <john.garry@huawei.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        "Paul A . Clarke" <pc@us.ibm.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Riccardo Mancini <rickyman7@gmail.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Kees Cook <keescook@chromium.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jacob Keller <jacob.e.keller@intel.com>,
        Zhen Lei <thunder.leizhen@huawei.com>,
        ToastC <mrtoastcheng@gmail.com>,
        Joakim Zhang <qiangqing.zhang@nxp.com>,
        Felix Fietkau <nbd@nbd.name>,
        Jiapeng Chong <jiapeng.chong@linux.alibaba.com>,
        Song Liu <songliubraving@fb.com>, Fabian Hemmer <copy@copy.sh>,
        Alexander Antonov <alexander.antonov@linux.intel.com>,
        Nicholas Fraser <nfraser@codeweavers.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Denys Zagorui <dzagorui@cisco.com>,
        Wan Jiabing <wanjiabing@vivo.com>,
        Thomas Richter <tmricht@linux.ibm.com>,
        Sumanth Korikkar <sumanthk@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Changbin Du <changbin.du@intel.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        Andrew Kilroy <andrew.kilroy@arm.com>
Cc:     Stephane Eranian <eranian@google.com>,
        Ian Rogers <irogers@google.com>
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Precedence: bulk

Document the data structures maintained by metricgroup.c and used by
stat-shadow.c for metric output.

Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/metricgroup.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/tools/perf/util/metricgroup.h b/tools/perf/util/metricgroup.h
index 88ba939a3082..3a51a84f440b 100644
--- a/tools/perf/util/metricgroup.h
+++ b/tools/perf/util/metricgroup.h
@@ -14,24 +14,51 @@ struct rblist;
 struct pmu_events_map;
 struct cgroup;
 
+/**
+ * A node in a rblist keyed by the evsel. The global rblist of metric events
+ * generally exists in perf_stat_config. The evsel is looked up in the rblist
+ * yielding a list of metric_expr.
+ */
 struct metric_event {
 	struct rb_node nd;
 	struct evsel *evsel;
 	struct list_head head; /* list of metric_expr */
 };
 
+/**
+ * A metric referenced by a metric_expr. When parsing a metric expression IDs
+ * will be looked up, matching either a value (from metric_events) or a
+ * metric_ref. A metric_ref will then be parsed recursively. The metric_refs and
+ * metric_events need to be known before parsing so that their values may be
+ * placed in the parse context for lookup.
+ */
 struct metric_ref {
 	const char *metric_name;
 	const char *metric_expr;
 };
 
+/**
+ * One in a list of metric_expr associated with an evsel. The data is used to
+ * generate a metric value during stat output.
+ */
 struct metric_expr {
 	struct list_head nd;
+	/** The expression to parse, for example, "instructions/cycles". */
 	const char *metric_expr;
+	/** The name of the meric such as "IPC". */
 	const char *metric_name;
+	/**
+	 * The "ScaleUnit" that scales and adds a unit to the metric during
+	 * output. For example, "6.4e-05MiB" means to scale the resulting metric
+	 * by 6.4e-05 (typically converting a unit like cache lines to something
+	 * more human intelligible) and then add "MiB" afterward when displayed.
+	 */
 	const char *metric_unit;
+	/** Null terminated array of events used by the metric. */
 	struct evsel **metric_events;
+	/** Null terminated array of referenced metrics. */
 	struct metric_ref *metric_refs;
+	/** A value substituted for '?' during parsing. */
 	int runtime;
 };
 
-- 
2.33.0.1079.g6e70778dc9-goog