devlib.collector: Add PerfettoCollector

Add a Collector for accessing Google's Perfetto tracing infrastructure.
The Collector takes a path to an on-device config file, starts tracing
in the background using the perfetto binary and then stops by killing
the tracing process.

Signed-off-by: Kajetan Puchalski <[email protected]>

Author: mrkajetanp

devlib/__init__.py

@@ -46,6 +46,7 @@
 from devlib.derived.fps import DerivedGfxInfoStats, DerivedSurfaceFlingerStats
 
 from devlib.collector.ftrace import FtraceCollector
+from devlib.collector.perfetto import PerfettoCollector
 from devlib.collector.perf import PerfCollector
 from devlib.collector.serial_trace import SerialTraceCollector
 from devlib.collector.dmesg import DmesgCollector

devlib/collector/perfetto.py

@@ -0,0 +1,71 @@
+#    Copyright 2023 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+import time
+import subprocess
+from shlex import quote
+
+from devlib.collector import (CollectorBase, CollectorOutput,
+                              CollectorOutputEntry)
+from devlib.exception import TargetStableError, HostError
+from devlib.utils.misc import check_output, which, memoized
+
+OUTPUT_PERFETTO_TRACE = 'trace.perfetto-trace'
+
+class PerfettoCollector(CollectorBase):
+
+    def __init__(self, target, config=None):
+        super().__init__(target)
+        self.target_output_file = target.path.join(self.target.working_directory, OUTPUT_PERFETTO_TRACE)
+        self.bg_cmd = None
+        self.config = config
+
+        if not self.target.is_installed('perfetto'):
+            raise TargetStableError('No perfetto found on device.')
+        self.target_binary = 'perfetto'
+
+    def start(self):
+        cmd = "cat {} | {} --txt -c - -o {}".format(
+            quote(self.config), quote(self.target_binary), quote(self.target_output_file)
+        )
+        # start tracing
+        if self.bg_cmd is None:
+            self.bg_cmd = self.target.background(cmd, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        else:
+            raise TargetStableError('Perfetto collector is not re-entrant')
+
+
+    def stop(self):
+        # stop tracing
+        self.bg_cmd.cancel()
+        self.bg_cmd = None
+
+    def set_output(self, output_path):
+        if os.path.isdir(output_path):
+            output_path = os.path.join(output_path, os.path.basename(self.target_output_file))
+        self.output_path = output_path
+
+    def get_data(self):
+        if self.output_path is None:
+            raise RuntimeError("Output path was not set.")
+        self.target.pull(self.target_output_file, self.output_path)
+        output = CollectorOutput()
+        if not os.path.isfile(self.output_path):
+            self.logger.warning('Perfetto trace not pulled from device.')
+        else:
+            output.append(CollectorOutputEntry(self.output_path, 'file'))
+        return output
+