Polish detail implement of dygraph data loader (#22878)

* polish detail implement of data loader, test=develop

* solve coverage ci problem, test=develop

paddle/fluid/imperative/data_loader.cc

@@ -129,9 +129,22 @@ void ThrowErrorIfLoadProcessFailed() {
           process_pid, infop.si_status));
     } else if (infop.si_code == CLD_KILLED ||
                infop.si_code == CLD_DUMPED) {  // killed by signal
-      PADDLE_THROW(platform::errors::Fatal(
-          "DataLoader process (pid %ld) exited is killed by signal: %s.",
-          process_pid, strsignal(infop.si_status)));
+      if (infop.si_status == SIGBUS) {
+        PADDLE_THROW(platform::errors::Fatal(
+            "DataLoader process (pid %ld) exited is killed by signal: %s.\n"
+            "  It may be caused by insufficient shared storage space. This "
+            "problem usually occurs when using docker as a development "
+            "environment.\n  Please use command `df -h` to check the storage "
+            "space of `/dev/shm`. Shared storage space needs to be greater "
+            "than (DataLoader Num * DataLoader queue capacity * 1 batch data "
+            "size).\n  You can solve this problem by increasing the shared "
+            "storage space or reducing the queue capacity appropriately.",
+            process_pid, strsignal(infop.si_status)));
+      } else {
+        PADDLE_THROW(platform::errors::Fatal(
+            "DataLoader process (pid %ld) exited is killed by signal: %s.",
+            process_pid, strsignal(infop.si_status)));
+      }
     }
   }
 }

python/paddle/fluid/reader.py

@@ -544,11 +544,12 @@ class DygraphGeneratorLoader(DataLoaderBase):
             # Set reader_thread
             self._thread_done_event = threading.Event()
             self._thread = threading.Thread(
-                target=self._reader_thread_loop_with_process)
+                target=self._reader_thread_loop_for_multiprocess)
             self._thread.daemon = True
             self._thread.start()
         else:
-            self._thread = threading.Thread(target=self._reader_thread_loop)
+            self._thread = threading.Thread(
+                target=self._reader_thread_loop_for_singleprocess)
             self._thread.daemon = True
             self._thread.start()
 
@@ -621,7 +622,7 @@ class DygraphGeneratorLoader(DataLoaderBase):
         except:
             six.reraise(*sys.exc_info())
 
-    def _reader_thread_loop_with_process(self):
+    def _reader_thread_loop_for_multiprocess(self):
         while not self._thread_done_event.is_set():
             try:
                 # NOTE: [ avoid hanging ] Even with carefully designed data dependencies 
@@ -636,11 +637,15 @@ class DygraphGeneratorLoader(DataLoaderBase):
                 # start trying to get data from queue. At this time, the child thread needs
                 # to wait slightly longer
                 tensor_list = self._data_queue.get(timeout=QUEUE_GET_TIMEOUT)
-            except queue.Empty:
+            except:
+                # NOTE [ avoid handing ] After adding the shared memory mechanism, not only
+                # the queue.Empty exception will occur here, but other exceptions will also
+                # occur, such as mmap failure. If it is not handled here, it will hang.
                 self._exit_thread_unexpectedly()
-                raise RuntimeError(
-                    "DataLoader reader thread has not read data for a long time (60s)."
+                logging.error(
+                    "DataLoader reader thread failed to read data from the multiprocessing.Queue."
                 )
+                six.reraise(*sys.exc_info())
 
             if not self._thread_done_event.is_set():
                 if tensor_list is not None:
@@ -656,7 +661,7 @@ class DygraphGeneratorLoader(DataLoaderBase):
                 else:
                     self._exit_thread_expectedly()
 
-    def _reader_thread_loop(self):
+    def _reader_thread_loop_for_singleprocess(self):
         try:
             for sample in self._batch_reader():
                 array = core.LoDTensorArray()

python/paddle/fluid/tests/unittests/CMakeLists.txt

@@ -197,7 +197,7 @@ list(REMOVE_ITEM TEST_OPS test_fuse_bn_act_pass)
 if (APPLE OR WIN32)
   list(REMOVE_ITEM TEST_OPS test_dataset)
   list(REMOVE_ITEM TEST_OPS test_dataset_dataloader)
-  list(REMOVE_ITEM TEST_OPS test_imperative_data_loader)
+  list(REMOVE_ITEM TEST_OPS test_imperative_data_loader_base)
   list(REMOVE_ITEM TEST_OPS test_imperative_data_loader_exception)
   list(REMOVE_ITEM TEST_OPS test_imperative_data_loader_process)
   list(REMOVE_ITEM TEST_OPS test_imperative_data_loader_fds_clear)
@@ -366,5 +366,7 @@ set_tests_properties(test_parallel_executor_test_while_train test_parallel_execu
         test_buffer_shared_memory_reuse_pass PROPERTIES LABELS "RUN_TYPE=DIST")
 
 if(NOT WIN32 AND NOT APPLE)
-    set_tests_properties(test_imperative_data_loader PROPERTIES LABELS "RUN_TYPE=EXCLUSIVE" RUN_SERIAL TRUE)
+    set_tests_properties(test_imperative_data_loader_base PROPERTIES LABELS "RUN_TYPE=EXCLUSIVE" RUN_SERIAL TRUE)
+    set_tests_properties(test_imperative_data_loader_exception PROPERTIES LABELS "RUN_TYPE=EXCLUSIVE" RUN_SERIAL TRUE)
+    set_tests_properties(test_imperative_data_loader_fds_clear PROPERTIES LABELS "RUN_TYPE=EXCLUSIVE" RUN_SERIAL TRUE)
 endif()

python/paddle/fluid/tests/unittests/test_imperative_data_loader_base.py

@@ -34,16 +34,6 @@ def sample_generator_creator(batch_size, batch_num):
     return __reader__
 
 
-def batch_generator_creator(batch_size, batch_num):
-    def __reader__():
-        for _ in range(batch_num):
-            batch_image, batch_label = get_random_images_and_labels(
-                [batch_size, 784], [batch_size, 1])
-            yield batch_image, batch_label
-
-    return __reader__
-
-
 class TestDygraphDataLoader(unittest.TestCase):
     def setUp(self):
         self.batch_size = 8
@@ -51,7 +41,7 @@ class TestDygraphDataLoader(unittest.TestCase):
         self.epoch_num = 1
         self.capacity = 5
 
-    def test_single_process_reader(self):
+    def test_single_process_loader(self):
         with fluid.dygraph.guard():
             loader = fluid.io.DataLoader.from_generator(
                 capacity=self.capacity, iterable=False, use_multiprocess=False)
@@ -66,7 +56,7 @@ class TestDygraphDataLoader(unittest.TestCase):
                     self.assertEqual(label.shape, [self.batch_size, 1])
                     self.assertEqual(relu.shape, [self.batch_size, 784])
 
-    def test_sample_genarator(self):
+    def test_multi_process_loader(self):
         with fluid.dygraph.guard():
             loader = fluid.io.DataLoader.from_generator(
                 capacity=self.capacity, use_multiprocess=True)
@@ -81,20 +71,6 @@ class TestDygraphDataLoader(unittest.TestCase):
                     self.assertEqual(label.shape, [self.batch_size, 1])
                     self.assertEqual(relu.shape, [self.batch_size, 784])
 
-    def test_batch_genarator(self):
-        with fluid.dygraph.guard():
-            loader = fluid.io.DataLoader.from_generator(
-                capacity=self.capacity, use_multiprocess=True)
-            loader.set_batch_generator(
-                batch_generator_creator(self.batch_size, self.batch_num),
-                places=fluid.CPUPlace())
-            for _ in range(self.epoch_num):
-                for image, label in loader():
-                    relu = fluid.layers.relu(image)
-                    self.assertEqual(image.shape, [self.batch_size, 784])
-                    self.assertEqual(label.shape, [self.batch_size, 1])
-                    self.assertEqual(relu.shape, [self.batch_size, 784])
-
 
 if __name__ == '__main__':
     unittest.main()

python/paddle/fluid/tests/unittests/test_imperative_signal_handler.py

@@ -38,7 +38,7 @@ def set_child_signal_handler(self, child_pid):
 
 
 class TestDygraphDataLoaderSingalHandler(unittest.TestCase):
-    def test_child_process_exit_will_error(self):
+    def test_child_process_exit_with_error(self):
         def __test_process__():
             core._set_process_signal_handler()
             sys.exit(1)
@@ -69,7 +69,25 @@ class TestDygraphDataLoaderSingalHandler(unittest.TestCase):
             set_child_signal_handler(id(self), test_process.pid)
             time.sleep(3)
         except core.EnforceNotMet as ex:
-            self.assertIn("FatalError", cpt.get_exception_message(ex))
+            self.assertIn("Segmentation fault", cpt.get_exception_message(ex))
+            exception = ex
+
+        self.assertIsNotNone(exception)
+
+    def test_child_process_killed_by_sigbus(self):
+        def __test_process__():
+            core._set_process_signal_handler()
+            os.kill(os.getpid(), signal.SIGBUS)
+
+        exception = None
+        try:
+            test_process = multiprocessing.Process(target=__test_process__)
+            test_process.start()
+
+            set_child_signal_handler(id(self), test_process.pid)
+            time.sleep(3)
+        except core.EnforceNotMet as ex:
+            self.assertIn("Bus error", cpt.get_exception_message(ex))
             exception = ex
 
         self.assertIsNotNone(exception)