[tip:perf/urgent] perf hists: Trim libtraceevent trace_seq buffers

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  887fa86d6fd7a45cee2d0f9d5f75026786d61df2
Gitweb:     http://git.kernel.org/tip/887fa86d6fd7a45cee2d0f9d5f75026786d61df2
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Fri, 5 Aug 2016 12:37:21 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 9 Aug 2016 10:46:56 -0300

perf hists: Trim libtraceevent trace_seq buffers

When we use libtraceevent to format trace event fields into printable
strings to use in hist entries it is important to trim it from the
default 4 KiB it starts with to what is really used, to reduce the
memory footprint, so use realloc(seq.buffer, seq.len + 1) when returning
the seq.buffer formatted with the fields contents.

Reported-and-Tested-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-t3hl7uxmilrkigzmc90rlhk2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/sort.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/sort.c b/tools/perf/util/sort.c
index 947d21f..3d3cb83 100644
--- a/tools/perf/util/sort.c
+++ b/tools/perf/util/sort.c
@@ -588,7 +588,11 @@ static char *get_trace_output(struct hist_entry *he)
 	} else {
 		pevent_event_info(&seq, evsel->tp_format, &rec);
 	}
-	return seq.buffer;
+	/*
+	 * Trim the buffer, it starts at 4KB and we're not going to
+	 * add anything more to this buffer.
+	 */
+	return realloc(seq.buffer, seq.len + 1);
 }
 
 static int64_t