linux-kernel - [PATCH 2/2] perf evlist: Support pipe mode display

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Message-Id: <20201210061302.88213-2-namhyung@kernel.org>
Date:   Thu, 10 Dec 2020 15:13:02 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: [PATCH 2/2] perf evlist: Support pipe mode display

Likewise, perf evlist command should print event attributes by reading
PERF_RECORD_HEADER_ATTR records.

Before:
  $ perf record -o- true | ./perf evlist -i-
  (prints nothing)

After:
  $ perf record -o- true | ./perf evlist -i-
  cycles:pppH

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-evlist.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-evlist.c b/tools/perf/builtin-evlist.c
index 98e992801251..4617b32c9c97 100644
--- a/tools/perf/builtin-evlist.c
+++ b/tools/perf/builtin-evlist.c
@@ -17,6 +17,14 @@
 #include "util/data.h"
 #include "util/debug.h"
 #include <linux/err.h>
+#include "util/tool.h"
+
+static int process_header_feature(struct perf_session *session __maybe_unused,
+				  union perf_event *event __maybe_unused)
+{
+	session_done = 1;
+	return 0;
+}
 
 static int __cmd_evlist(const char *file_name, struct perf_attr_details *details)
 {
@@ -27,12 +35,20 @@ static int __cmd_evlist(const char *file_name, struct perf_attr_details *details
 		.mode      = PERF_DATA_MODE_READ,
 		.force     = details->force,
 	};
+	struct perf_tool tool = {
+		/* only needed for pipe mode */
+		.attr = perf_event__process_attr,
+		.feature = process_header_feature,
+	};
 	bool has_tracepoint = false;
 
-	session = perf_session__new(&data, 0, NULL);
+	session = perf_session__new(&data, 0, &tool);
 	if (IS_ERR(session))
 		return PTR_ERR(session);
 
+	if (data.is_pipe)
+		perf_session__process_events(session);
+
 	evlist__for_each_entry(session->evlist, pos) {
 		evsel__fprintf(pos, details, stdout);
 
-- 
2.29.2.576.ga3fc446d84-goog