[PATCH 12/12] perf header: Use last modification time for timestamp

Arnaldo Carvalho de Melo
2020-01-16T13:49:07Z

From: Michael Petlan <mpetlan@redhat.com>

Using .st_ctime clobbers the timestamp information in perf report header
whenever any operation is done with the file. Even tar-ing and untar-ing
the perf.data file (which preserves the file last modification timestamp)
doesn't prevent that:

[Michael@Diego tmp]$ ls -l perf.data
-> -rw-------. 1 Michael Michael 169888 Dec 2 15:23 perf.data

[Michael@Diego tmp]$ perf report --header-only
# ========
-> # captured on : Mon Dec 2 15:23:42 2019
[...]

[Michael@Diego tmp]$ tar c perf.data | xz > perf.data.tar.xz
[Michael@Diego tmp]$ mkdir aaa
[Michael@Diego tmp]$ cd aaa
[Michael@Diego aaa]$ xzcat ../perf.data.tar.xz | tar x
[Michael@Diego aaa]$ ls -l -a
total 172
drwxrwxr-x. 2 Michael Michael 23 Jan 14 11:26 .
drwxrwxr-x. 6 Michael Michael 4096 Jan 14 11:26 ..
-> -rw-------. 1 Michael Michael 169888 Dec 2 15:23 perf.data

[Michael@Diego aaa]$ perf report --header-only
# ========
-> # captured on : Tue Jan 14 11:26:16 2020
[...]

When using .st_mtime instead, correct information is printed:

[Michael@Diego aaa]$ ~/acme/tools/perf/perf report --header-only
# ========
-> # captured on : Mon Dec 2 15:23:42 2019
[...]

Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
LPU-Reference: 20200114104236.31555-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/header.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 93ad27830e2b..4246e7447e54 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2922,7 +2922,7 @@ int perf_header__fprintf_info(struct perf_session *session, FILE *fp, bool full)
if (ret == -1)
return -1;

- stctime = st.st_ctime;
+ stctime = st.st_mtime;
fprintf(fp, "# captured on : %s", ctime(&stctime));

fprintf(fp, "# header version : %u\n", header->version);
--
2.21.1