linux-kernel - [PATCH 13/18] perf tools: Stop copying kallsyms into the perf.data file header

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Message-Id: <1437703111-4930-14-git-send-email-acme@kernel.org>
Date:	Thu, 23 Jul 2015 22:58:26 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Borislav Petkov <bp@...e.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 13/18] perf tools: Stop copying kallsyms into the perf.data file header

From: Arnaldo Carvalho de Melo <acme@...hat.com>

Since we now ask libtraceevent, the only user of this payload, to use
perf's symbol resolution routines, there is no need to carry about
~4.5MB per perf.data when we can get it from one of the places the perf
symbol resolution looks for that symtab (debuginfo, ~/.debug/,
/proc/kallsyms, --symfs, etc), using the kernel and modules build-ids to
make sure the right table is used.

Acked-by: David Ahern <dsahern@...il.com>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Borislav Petkov <bp@...e.de>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Link: http://lkml.kernel.org/n/tip-h89ituf9rso2rv1v7kjrbeda@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/trace-event-info.c | 22 ++++++++--------------
 1 file changed, 8 insertions(+), 14 deletions(-)

diff --git a/tools/perf/util/trace-event-info.c b/tools/perf/util/trace-event-info.c
index eb72716017ac..22245986e59e 100644
--- a/tools/perf/util/trace-event-info.c
+++ b/tools/perf/util/trace-event-info.c
@@ -341,20 +341,14 @@ out:
 
 static int record_proc_kallsyms(void)
 {
-	unsigned int size;
-	const char *path = "/proc/kallsyms";
-	struct stat st;
-	int ret, err = 0;
-
-	ret = stat(path, &st);
-	if (ret < 0) {
-		/* not found */
-		size = 0;
-		if (write(output_fd, &size, 4) != 4)
-			err = -EIO;
-		return err;
-	}
-	return record_file(path, 4);
+	unsigned long long size = 0;
+	/*
+	 * Just to keep older perf.data file parsers happy, record a zero
+	 * sized kallsyms file, i.e. do the same thing that was done when
+	 * /proc/kallsyms (or something specified via --kallsyms, in a
+	 * different path) couldn't be read.
+	 */
+	return write(output_fd, &size, 4) != 4 ? -EIO : 0;
 }
 
 static int record_ftrace_printk(void)
-- 
2.1.0

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