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Subject[PATCH 03/47] perf evlist: Use PERF_EVENT_IOC_ID perf ioctl to read event id
Date
From: Jiri Olsa <jolsa@redhat.com>

Changing the way we retrieve the event ID. Instead of parsing out
the ID out of the read data, using the PERF_EVENT_IOC_ID ioctl.

Keeping the old way in place to support kernels without
PERF_EVENT_IOC_ID ioctl support.

This will be useful for retrieving the event ID for events
with PERF_FORMAT_GROUP read format set, where it's impossible
to get correct event id out of the read call data.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-psgb4n7kte8e6tfenbe7nj2h@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evlist.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 42ea4e9..0d3b739 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -302,6 +302,17 @@ static int perf_evlist__id_add_fd(struct perf_evlist *evlist,
{
u64 read_data[4] = { 0, };
int id_idx = 1; /* The first entry is the counter value */
+ u64 id;
+ int ret;
+
+ ret = ioctl(fd, PERF_EVENT_IOC_ID, &id);
+ if (!ret)
+ goto add;
+
+ if (errno != ENOTTY)
+ return -1;
+
+ /* Legacy way to get event id.. All hail to old kernels! */

if (!(evsel->attr.read_format & PERF_FORMAT_ID) ||
read(fd, &read_data, sizeof(read_data)) == -1)
@@ -312,7 +323,10 @@ static int perf_evlist__id_add_fd(struct perf_evlist *evlist,
if (evsel->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
++id_idx;

- perf_evlist__id_add(evlist, evsel, cpu, thread, read_data[id_idx]);
+ id = read_data[id_idx];
+
+ add:
+ perf_evlist__id_add(evlist, evsel, cpu, thread, id);
return 0;
}

--
1.8.1.4


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