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Subject[RFC 1/4] perf script python: Allocate memory only if handler exists
Date
Avoid allocating memory if hook handler is not available. This saves
unused memory allocation and simplifies error path.

Let handler in python_process_tracepoint point to either tracepoint
specific or trace_unhandled hook. Use dict to check if handler points to
trace_unhandled.

Remove the exit label in python_process_general_event and return when no
handler is available.

Signed-off-by: Arun Kalyanasundaram <arunkaly@google.com>
---
.../util/scripting-engines/trace-event-python.c | 38 +++++++++++++---------
1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 57b7a00e6f16..8a8f4829d3e2 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c
@@ -407,10 +407,7 @@ static void python_process_tracepoint(struct perf_sample *sample,
void *data = sample->raw_data;
unsigned long long nsecs = sample->time;
const char *comm = thread__comm_str(al->thread);
-
- t = PyTuple_New(MAX_FIELDS);
- if (!t)
- Py_FatalError("couldn't create Python tuple");
+ const char *default_handler_name = "trace_unhandled";

if (!event) {
snprintf(handler_name, sizeof(handler_name),
@@ -427,10 +424,19 @@ static void python_process_tracepoint(struct perf_sample *sample,

handler = get_handler(handler_name);
if (!handler) {
+ handler = get_handler(default_handler_name);
+ if (!handler)
+ return;
dict = PyDict_New();
if (!dict)
Py_FatalError("couldn't create Python dict");
}
+
+ t = PyTuple_New(MAX_FIELDS);
+ if (!t)
+ Py_FatalError("couldn't create Python tuple");
+
+
s = nsecs / NSEC_PER_SEC;
ns = nsecs - s * NSEC_PER_SEC;

@@ -445,7 +451,7 @@ static void python_process_tracepoint(struct perf_sample *sample,
/* ip unwinding */
callchain = python_process_callchain(sample, evsel, al);

- if (handler) {
+ if (!dict) {
PyTuple_SetItem(t, n++, PyInt_FromLong(cpu));
PyTuple_SetItem(t, n++, PyInt_FromLong(s));
PyTuple_SetItem(t, n++, PyInt_FromLong(ns));
@@ -484,23 +490,23 @@ static void python_process_tracepoint(struct perf_sample *sample,
} else { /* FIELD_IS_NUMERIC */
obj = get_field_numeric_entry(event, field, data);
}
- if (handler)
+ if (!dict)
PyTuple_SetItem(t, n++, obj);
else
pydict_set_item_string_decref(dict, field->name, obj);

}

- if (!handler)
+ if (dict)
PyTuple_SetItem(t, n++, dict);

if (_PyTuple_Resize(&t, n) == -1)
Py_FatalError("error resizing Python tuple");

- if (handler) {
+ if (!dict) {
call_object(handler, t, handler_name);
} else {
- try_call_object("trace_unhandled", t);
+ call_object(handler, t, default_handler_name);
Py_DECREF(dict);
}

@@ -799,6 +805,12 @@ static void python_process_general_event(struct perf_sample *sample,
static char handler_name[64];
unsigned n = 0;

+ snprintf(handler_name, sizeof(handler_name), "%s", "process_event");
+
+ handler = get_handler(handler_name);
+ if (!handler)
+ return;
+
/*
* Use the MAX_FIELDS to make the function expandable, though
* currently there is only one item for the tuple.
@@ -815,12 +827,6 @@ static void python_process_general_event(struct perf_sample *sample,
if (!dict_sample)
Py_FatalError("couldn't create Python dictionary");

- snprintf(handler_name, sizeof(handler_name), "%s", "process_event");
-
- handler = get_handler(handler_name);
- if (!handler)
- goto exit;
-
pydict_set_item_string_decref(dict, "ev_name", PyString_FromString(perf_evsel__name(evsel)));
pydict_set_item_string_decref(dict, "attr", PyString_FromStringAndSize(
(const char *)&evsel->attr, sizeof(evsel->attr)));
@@ -861,7 +867,7 @@ static void python_process_general_event(struct perf_sample *sample,
Py_FatalError("error resizing Python tuple");

call_object(handler, t, handler_name);
-exit:
+
Py_DECREF(dict);
Py_DECREF(t);
}
--
2.13.2.932.g7449e964c-goog
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