Re: [PATCH 2/5] perf evlist: Add evlist__findnew_tracking_event() helper

From: Yang Jihong
Date: Wed Jul 12 2023 - 10:32:48 EST


Hello,

On 2023/7/11 21:13, Adrian Hunter wrote:
On 4/07/23 10:42, Yang Jihong wrote:
Currently, intel-bts, intel-pt, and arm-spe may add a dummy event for
tracking to the evlist. We may need to search for the dummy event for
some settings. Therefore, add evlist__findnew_tracking_event() helper.

Signed-off-by: Yang Jihong <yangjihong1@xxxxxxxxxx>
---
tools/perf/builtin-record.c | 11 +++--------
tools/perf/util/evlist.c | 17 +++++++++++++++++
tools/perf/util/evlist.h | 1 +
3 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index aec18db7ff23..8872cd037f2c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1295,14 +1295,9 @@ static int record__open(struct record *rec)
*/
if (opts->target.initial_delay || target__has_cpu(&opts->target) ||
perf_pmus__num_core_pmus() > 1) {
- pos = evlist__get_tracking_event(evlist);
- if (!evsel__is_dummy_event(pos)) {
- /* Set up dummy event. */
- if (evlist__add_dummy(evlist))
- return -ENOMEM;
- pos = evlist__last(evlist);
- evlist__set_tracking_event(evlist, pos);
- }
+ pos = evlist__findnew_tracking_event(evlist);
+ if (!pos)
+ return -ENOMEM;
/*
* Enable the dummy event when the process is forked for
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 7ef43f72098e..4621ddaeb8f3 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1694,6 +1694,23 @@ void evlist__set_tracking_event(struct evlist *evlist, struct evsel *tracking_ev
tracking_evsel->tracking = true;
}
+struct evsel *evlist__findnew_tracking_event(struct evlist *evlist)
+{
+ struct evsel *evsel;
+
+ evsel = evlist__get_tracking_event(evlist);
+ if (!evsel__is_dummy_event(evsel)) {
+ /* Set up dummy event. */
+ if (evlist__add_dummy(evlist))

evlist__add_dummy() does not exclude_kernel so it
will end up relying on evsel__fallback() to work in
cases where the user does not have kernel access.

evlist__add_aux_dummy() is probably better suited.
Consequently perhaps pass system_wide as
a parameter to evlist__findnew_tracking_event() and
deal with that all inside evlist__findnew_tracking_event()

OK. These two points will be modified in the next version.

Thanks,
Yang