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[PATCH 1/1] perf header: Fixup reading of HEADER_NRCPUS feature

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  [PATCH 1/1] perf header: Fixup reading of HEADER_NRCPUS feature Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-13 17:30 +0200

#1223705 — [PATCH 1/1] perf header: Fixup reading of HEADER_NRCPUS feature

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

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

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 41814547da15..fce6634aebe2 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1438,7 +1438,7 @@ static int process_nrcpus(struct perf_file_section *section __maybe_unused,
 	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))
@@ -1447,7 +1447,7 @@ static int process_nrcpus(struct perf_file_section *section __maybe_unused,
 	if (ph->needs_swap)
 		nr = bswap_32(nr);
 
-	ph->env.nr_cpus_avail = nr;
+	ph->env.nr_cpus_online = nr;
 	return 0;
 }
 
-- 
2.1.0

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