perf script python: Allocate memory only if handler exists

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>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Carrillo-Cisneros <davidcc@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Seongjae Park <sj38.park@gmail.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20170721220422.63962-2-arunkaly@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files 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);
 }