[PATCH 3.10 02/54] perf header: Fixup reading of HEADER_NRCPUS feature

Greg Kroah-Hartman
2015-10-18T03:32:21Z

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

commit caa470475d9b59eeff093ae650800d34612c4379 upstream.

The original patch introducing this header wrote the number of CPUs available
and online in one order and then swapped those values when reading, fix it.

Before:

# perf record usleep 1
# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 4
# nrcpus avail : 4
# echo 0 > /sys/devices/system/cpu/cpu2/online
# perf record usleep 1
# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 4
# nrcpus avail : 3
# echo 0 > /sys/devices/system/cpu/cpu1/online
# perf record usleep 1
# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 4
# nrcpus avail : 2

After the fix, bringing back the CPUs online:

# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 2
# nrcpus avail : 4
# echo 1 > /sys/devices/system/cpu/cpu2/online
# perf record usleep 1
# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 3
# nrcpus avail : 4
# echo 1 > /sys/devices/system/cpu/cpu1/online
# perf record usleep 1
# perf report --header-only | grep 'nrcpus \(online\|avail\)'
# nrcpus online : 4
# nrcpus avail : 4

Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: fbe96f29ce4b ("perf tools: Make perf.data more self-descriptive (v8)")
Link: http://lkml.kernel.org/r/20150911153323.GP23511@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
tools/perf/util/header.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1729,7 +1729,7 @@ static int process_nrcpus(struct perf_fi
if (ph->needs_swap)
nr = bswap_32(nr);

- ph->env.nr_cpus_online = nr;
+ ph->env.nr_cpus_avail = nr;

ret = readn(fd, &nr, sizeof(nr));
if (ret != sizeof(nr))
@@ -1738,7 +1738,7 @@ static int process_nrcpus(struct perf_fi
if (ph->needs_swap)
nr = bswap_32(nr);

- ph->env.nr_cpus_avail = nr;
+ ph->env.nr_cpus_online = nr;
return 0;
}