perf script: Expose usage of the callchain db export via the python api

This change allows python scripts to be able to utilize the recent
changes to the db export api allowing the export of call_paths derived
from sampled callchains. These call paths are also now associated with
the samples from which they were derived.

- This feature is enabled by setting "perf_db_export_callchains" to true

- When enabled, samples that have callchain information will have the
callchains exported via call_path_table

- The call_path_id field is added to sample_table to enable association of
samples with the corresponding callchain stored in the call paths
table. A call_path_id of 0 will be exported if there is no
corresponding callchain.

- When "perf_db_export_callchains" and "perf_db_export_calls" are both
set to True, the call path root data structure will be shared. This
prevents duplicating of data and call path ids that would result from
building two separate call path trees in memory.

- The call_return_processor structure definition was relocated to the header
file to make its contents visible to db-export.c. This enables the
sharing of call path trees between the two features, as mentioned
above.

This change is visible to python scripts using the python db export api.

The change is backwards compatible with scripts written against the
previous API, assuming that the scripts model the sample_table function
after the one in export-to-postgresql.py script by allowing for
additional arguments to be added in the future. ie. using *x as the
final argument of the sample_table function.

Signed-off-by: Chris Phlipot <[e-mail]>
Acked-by: Adrian Hunter <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/scripting-engines/trace-event-python.c

···
 	struct tables *tables = container_of(dbe, struct tables, dbe);
 	PyObject *t;
 
-	t = tuple_new(21);
+	t = tuple_new(22);
 
 	tuple_set_u64(t, 0, es->db_id);
 	tuple_set_u64(t, 1, es->evsel->db_id);
···
 	tuple_set_u64(t, 18, es->sample->data_src);
 	tuple_set_s32(t, 19, es->sample->flags & PERF_BRANCH_MASK);
 	tuple_set_s32(t, 20, !!(es->sample->flags & PERF_IP_FLAG_IN_TX));
+	tuple_set_u64(t, 21, es->call_path_id);
 
 	call_object(tables->sample_handler, t, "sample_table");
 
···
 {
 	const char *perf_db_export_mode = "perf_db_export_mode";
 	const char *perf_db_export_calls = "perf_db_export_calls";
-	PyObject *db_export_mode, *db_export_calls;
+	const char *perf_db_export_callchains = "perf_db_export_callchains";
+	PyObject *db_export_mode, *db_export_calls, *db_export_callchains;
 	bool export_calls = false;
+	bool export_callchains = false;
 	int ret;
 
 	memset(tables, 0, sizeof(struct tables));
···
 	if (!ret)
 		return;
 
+	/* handle export calls */
 	tables->dbe.crp = NULL;
 	db_export_calls = PyDict_GetItemString(main_dict, perf_db_export_calls);
 	if (db_export_calls) {
···
 			call_return_processor__new(python_process_call_return,
 						   &tables->dbe);
 		if (!tables->dbe.crp)
+			Py_FatalError("failed to create calls processor");
+	}
+
+	/* handle export callchains */
+	tables->dbe.cpr = NULL;
+	db_export_callchains = PyDict_GetItemString(main_dict,
+						    perf_db_export_callchains);
+	if (db_export_callchains) {
+		ret = PyObject_IsTrue(db_export_callchains);
+		if (ret == -1)
+			handler_call_die(perf_db_export_callchains);
+		export_callchains = !!ret;
+	}
+
+	if (export_callchains) {
+		/*
+		 * Attempt to use the call path root from the call return
+		 * processor, if the call return processor is in use. Otherwise,
+		 * we allocate a new call path root. This prevents exporting
+		 * duplicate call path ids when both are in use simultaniously.
+		 */
+		if (tables->dbe.crp)
+			tables->dbe.cpr = tables->dbe.crp->cpr;
+		else
+			tables->dbe.cpr = call_path_root__new();
+
+		if (!tables->dbe.cpr)
 			Py_FatalError("failed to create calls processor");
 	}
 

tools/perf/util/thread-stack.c

···
 #include "call-path.h"
 #include "thread-stack.h"
 
-/**
- * struct call_return_processor - provides a call-back to consume call-return
- *                                information.
- * @cpr: call path root
- * @process: call-back that accepts call/return information
- * @data: anonymous data for call-back
- */
-struct call_return_processor {
-	struct call_path_root *cpr;
-	int (*process)(struct call_return *cr, void *data);
-	void *data;
-};
-
 #define STACK_GROWTH 2048
 
 /**

tools/perf/util/thread-stack.h

···
 struct ip_callchain;
 struct symbol;
 struct dso;
-struct call_return_processor;
 struct comm;
 struct perf_sample;
 struct addr_location;
···
 	u64 return_ref;
 	u64 db_id;
 	u32 flags;
+};
+
+/**
+ * struct call_return_processor - provides a call-back to consume call-return
+ *                                information.
+ * @cpr: call path root
+ * @process: call-back that accepts call/return information
+ * @data: anonymous data for call-back
+ */
+struct call_return_processor {
+	struct call_path_root *cpr;
+	int (*process)(struct call_return *cr, void *data);
+	void *data;
 };
 
 int thread_stack__event(struct thread *thread, u32 flags, u64 from_ip,