Make subbuffer size configurable with Trace action (#51)

Signed-off-by: Christopher Wecht <cwecht@mailbox.org>
Co-authored-by: Christophe Bedard <christophe.bedard@apex.ai>

test_tracetools_launch/test/test_tracetools_launch/test_trace_action.py

@@ -64,13 +64,17 @@ def _check_trace_action(
         tmpdir,
         session_name: str = 'my-session-name',
         events_ust: List[str] = ['ros2:*', '*'],
+        subbuffer_size_ust: int = 524288,
+        subbuffer_size_kernel: int = 1048576,
     ) -> None:
         self.assertEqual(session_name, action.session_name)
         self.assertEqual(tmpdir, action.base_path)
         self.assertTrue(action.trace_directory.startswith(tmpdir))
         self.assertEqual([], action.events_kernel)
         self.assertEqual(events_ust, action.events_ust)
         self.assertTrue(pathlib.Path(tmpdir).exists())
+        self.assertEqual(subbuffer_size_ust, action.subbuffer_size_ust)
+        self.assertEqual(subbuffer_size_kernel, action.subbuffer_size_kernel)
 
     def test_action(self) -> None:
         self.assertIsNone(os.environ.get('LD_PRELOAD'))
@@ -85,6 +89,8 @@ def test_action(self) -> None:
                 'ros2:*',
                 '*',
             ],
+            subbuffer_size_ust=524288,
+            subbuffer_size_kernel=1048576,
         )
         self._assert_launch_no_errors([action])
         self._check_trace_action(action, tmpdir)
@@ -104,6 +110,8 @@ def test_action_frontend_xml(self) -> None:
                     base-path="{}"
                     events-kernel=""
                     events-ust="ros2:* *"
+                    subbuffer-size-ust="524288"
+                    subbuffer-size-kernel="1048576"
                 />
             </launch>
             """.format(tmpdir)
@@ -130,6 +138,8 @@ def test_action_frontend_yaml(self) -> None:
                 base-path: {}
                 events-kernel: ""
                 events-ust: ros2:* *
+                subbuffer-size-ust: 524288
+                subbuffer-size-kernel: 1048576
             """.format(tmpdir)
         )
 
@@ -158,6 +168,8 @@ def test_action_context_per_domain(self) -> None:
                 'kernel': [],
                 'userspace': ['vpid', 'vtid'],
             },
+            subbuffer_size_ust=524288,
+            subbuffer_size_kernel=1048576,
         )
         self._assert_launch_no_errors([action])
         self._check_trace_action(action, tmpdir)
@@ -202,6 +214,8 @@ def test_action_substitutions(self) -> None:
                     TextSubstitution(text='vtid'),
                 ],
             },
+            subbuffer_size_ust=524288,
+            subbuffer_size_kernel=1048576,
         )
         self._assert_launch_no_errors([session_name_arg, action])
         self._check_trace_action(action, tmpdir)
@@ -234,6 +248,8 @@ def test_action_ld_preload(self) -> None:
                 'lttng_ust_pthread:*',
                 'lttng_ust_dl:*',
             ],
+            subbuffer_size_ust=524288,
+            subbuffer_size_kernel=1048576,
         )
         node_ping_action = Node(
             package='test_tracetools',

tracetools_launch/tracetools_launch/action.py

@@ -114,6 +114,8 @@ def __init__(
         context_fields:
             Union[Iterable[SomeSubstitutionsType], Dict[str, Iterable[SomeSubstitutionsType]]]
             = names.DEFAULT_CONTEXT,
+        subbuffer_size_ust: int = 8 * 4096,
+        subbuffer_size_kernel: int = 32 * 4096,
         **kwargs,
     ) -> None:
         """
@@ -139,6 +141,10 @@ def __init__(
             if it's a list or a set, the context fields are enabled for both kernel and userspace;
             if it's a dictionary: { domain type string -> context fields list }
                 with the domain type string being either 'kernel' or 'userspace'
+        :param subbuffer_size_ust: the size of the subbuffers (defaults to 8 times the usual page
+            size)
+        :param subbuffer_size_kernel: the size of the subbuffers (defaults to 32 times the usual
+            page size)
         """
         super().__init__(**kwargs)
         self.__logger = logging.get_logger(__name__)
@@ -157,6 +163,8 @@ def __init__(
             if isinstance(context_fields, dict) \
             else [normalize_to_list_of_substitutions(field) for field in context_fields]
         self.__ld_preload_actions: List[LdPreload] = []
+        self.__subbuffer_size_ust = subbuffer_size_ust
+        self.__subbuffer_size_kernel = subbuffer_size_kernel
 
     @property
     def session_name(self):
@@ -182,6 +190,14 @@ def events_kernel(self):
     def context_fields(self):
         return self.__context_fields
 
+    @property
+    def subbuffer_size_ust(self):
+        return self.__subbuffer_size_ust
+
+    @property
+    def subbuffer_size_kernel(self):
+        return self.__subbuffer_size_kernel
+
     @classmethod
     def _parse_cmdline(
         cls,
@@ -270,6 +286,14 @@ def parse(cls, entity: Entity, parser: Parser):
         if context_fields is not None:
             kwargs['context_fields'] = cls._parse_cmdline(context_fields, parser) \
                 if context_fields else []
+        subbuffer_size_ust = entity.get_attr(
+            'subbuffer-size-ust', data_type=int, optional=True, can_be_str=False)
+        if subbuffer_size_ust is not None:
+            kwargs['subbuffer_size_ust'] = subbuffer_size_ust
+        subbuffer_size_kernel = entity.get_attr(
+            'subbuffer-size-kernel', data_type=int, optional=True, can_be_str=False)
+        if subbuffer_size_kernel is not None:
+            kwargs['subbuffer_size_kernel'] = subbuffer_size_kernel
 
         return cls, kwargs
 
@@ -380,6 +404,8 @@ def _setup(self) -> bool:
             ros_events=self.__events_ust,
             kernel_events=self.__events_kernel,
             context_fields=self.__context_fields,
+            subbuffer_size_ust=self.__subbuffer_size_ust,
+            subbuffer_size_kernel=self.__subbuffer_size_kernel,
         )
         if self.__trace_directory is None:
             return False
@@ -388,6 +414,8 @@ def _setup(self) -> bool:
         self.__logger.debug(f'Kernel events: {self.__events_kernel}')
         self.__logger.debug(f'Context fields: {self.__context_fields}')
         self.__logger.debug(f'LD_PRELOAD: {self.__ld_preload_actions}')
+        self.__logger.debug(f'UST subbuffer size: {self.__subbuffer_size_ust}')
+        self.__logger.debug(f'Kernel subbuffer size: {self.__subbuffer_size_kernel}')
         return True
 
     def _destroy(self, event: Event, context: LaunchContext) -> None:
@@ -403,5 +431,7 @@ def __repr__(self):
             f'events_ust={self.__events_ust}, '
             f'events_kernel={self.__events_kernel}, '
             f'context_fields={self.__context_fields}, '
-            f'ld_preload_actions={self.__ld_preload_actions})'
+            f'ld_preload_actions={self.__ld_preload_actions}, '
+            f'subbuffer_size_ust={self.__subbuffer_size_ust}, '
+            f'subbuffer_size_kernel={self.__subbuffer_size_kernel})'
         )

tracetools_trace/tracetools_trace/tools/lttng_impl.py

@@ -73,6 +73,8 @@ def setup(
     context_fields: Union[List[str], Set[str], Dict[str, List[str]]] = DEFAULT_CONTEXT,
     channel_name_ust: str = 'ros2',
     channel_name_kernel: str = 'kchan',
+    subbuffer_size_ust: int = 8 * 4096,
+    subbuffer_size_kernel: int = 32 * 4096,
 ) -> Optional[str]:
     """
     Set up LTTng session, with events and context.
@@ -91,6 +93,10 @@ def setup(
         if it's a dictionary: { domain type string -> context fields list }
     :param channel_name_ust: the UST channel name
     :param channel_name_kernel: the kernel channel name
+    :param subbuffer_size_ust: the size of the subbuffers for userspace events (defaults to 8 times
+        the usual page size)
+    :param subbuffer_size_kernel: the size of the subbuffers for kernel events (defaults to 32
+        times the usual page size, since there can be way more kernel events than UST events)
     :return: the full path to the trace directory, or `None` if initialization failed
     """
     # Check if there is a session daemon running
@@ -142,10 +148,9 @@ def setup(
         channel_ust.name = channel_name_ust
         # Discard, do not overwrite
         channel_ust.attr.overwrite = 0
-        # 2 sub-buffers of 8 times the usual page size
         # We use 2 sub-buffers because the number of sub-buffers is pointless in discard mode,
         # and switching between sub-buffers introduces noticeable CPU overhead
-        channel_ust.attr.subbuf_size = 8 * 4096
+        channel_ust.attr.subbuf_size = subbuffer_size_ust
         channel_ust.attr.num_subbuf = 2
         # Ignore switch timer interval and use read timer instead
         channel_ust.attr.switch_timer_interval = 0
@@ -162,9 +167,7 @@ def setup(
         channel_kernel.name = channel_name_kernel
         # Discard, do not overwrite
         channel_kernel.attr.overwrite = 0
-        # 2 sub-buffers of 32 times the usual page size, since
-        # there can be way more kernel events than UST events
-        channel_kernel.attr.subbuf_size = 32 * 4096
+        channel_kernel.attr.subbuf_size = subbuffer_size_kernel
         channel_kernel.attr.num_subbuf = 2
         # Ignore switch timer interval and use read timer instead
         channel_kernel.attr.switch_timer_interval = 0