Re: [PATCH 02/37] perf record: Use a software dummy event to track task/mmap events

From: David Ahern
Date: Fri Dec 26 2014 - 11:27:19 EST


On 12/24/14 12:14 AM, Namhyung Kim wrote:
Prepend a software dummy event into evlist to track task/comm/mmap
events separately. This is a preparation of multi-file/thread support
which will come later.

Are you are making this the first event because of how perf internals are coded -- that the first event tracks tasks events? With the tracking bit in evsel you should not need to do that. Is there another reason?

---8<---

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index cfbe2b99b9aa..72dff295237e 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -193,6 +193,44 @@ int perf_evlist__add_default(struct perf_evlist *evlist)
return -ENOMEM;
}

+int perf_evlist__prepend_dummy(struct perf_evlist *evlist)
+{
+ struct perf_event_attr attr = {
+ .type = PERF_TYPE_SOFTWARE,
+ .config = PERF_COUNT_SW_DUMMY,
+ };
+ struct perf_evsel *evsel, *pos;
+
+ event_attr_init(&attr);
+
+ evsel = perf_evsel__new(&attr);
+ if (evsel == NULL)
+ goto error;
+
+ /* use strdup() because free(evsel) assumes name is allocated */
+ evsel->name = strdup("dummy");
+ if (!evsel->name)
+ goto error_free;
+
+ list_for_each_entry(pos, &evlist->entries, node) {
+ pos->idx += 1;
+ pos->tracking = false;
+ }
+
+ list_add(&evsel->node, &evlist->entries);
+ evsel->idx = 0;
+ evsel->tracking = true;

perf_evlist__set_tracking_event()?

David

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