linux-kernel - [tip:perf/core] perf tools: Stop copying kallsyms into the perf.data file header

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Date:	Wed, 29 Jul 2015 01:14:03 -0700
From:	tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	acme@...hat.com, linux-kernel@...r.kernel.org, eranian@...gle.com,
	namhyung@...nel.org, fweisbec@...il.com, adrian.hunter@...el.com,
	hpa@...or.com, jolsa@...hat.com, bp@...e.de, mingo@...nel.org,
	rostedt@...dmis.org, dsahern@...il.com, tglx@...utronix.de
Subject: [tip:perf/core] perf tools:
  Stop copying kallsyms into the perf.data file header

Commit-ID:  6e5259e9b5b711b325a8455feb3ed27cdd0af0da
Gitweb:     http://git.kernel.org/tip/6e5259e9b5b711b325a8455feb3ed27cdd0af0da
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Wed, 22 Jul 2015 17:02:18 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Thu, 23 Jul 2015 22:51:12 -0300

perf tools: Stop copying kallsyms into the perf.data file header

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 eb72716..2224598 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)
--
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