[PATCH 2/4] perf tools: Add perf_evsel__read_size function

From: Jiri Olsa
Date: Fri Jul 21 2017 - 08:13:07 EST


Currently we use the size of struct perf_counts_values
to read the event, which prevents us to put any new
member to the struct.

Adding perf_evsel__read_size to return size of the
buffer needed for event read.

Link: http://lkml.kernel.org/n/tip-cfc3dmil3tlzezzxtyi9f38m@xxxxxxxxxxxxxx
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
tools/perf/util/evsel.c | 29 ++++++++++++++++++++++++++++-
1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 450b5fadf8cb..4dd0fcc06db9 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1261,15 +1261,42 @@ void perf_counts_values__scale(struct perf_counts_values *count,
*pscaled = scaled;
}

+static int perf_evsel__read_size(struct perf_evsel *evsel)
+{
+ u64 read_format = evsel->attr.read_format;
+ int entry = sizeof(u64); /* value */
+ int size = 0;
+ int nr = 1;
+
+ if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
+ size += sizeof(u64);
+
+ if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
+ size += sizeof(u64);
+
+ if (read_format & PERF_FORMAT_ID)
+ entry += sizeof(u64);
+
+ if (read_format & PERF_FORMAT_GROUP) {
+ nr = evsel->nr_members;
+ size += sizeof(u64);
+ }
+
+ size += entry * nr;
+ return size;
+}
+
int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread,
struct perf_counts_values *count)
{
+ size_t size = perf_evsel__read_size(evsel);
+
memset(count, 0, sizeof(*count));

if (FD(evsel, cpu, thread) < 0)
return -EINVAL;

- if (readn(FD(evsel, cpu, thread), count, sizeof(*count)) <= 0)
+ if (readn(FD(evsel, cpu, thread), count->values, size) <= 0)
return -errno;

return 0;
--
2.9.4