Add basic benchmark scheduler

This patch introduces the BenchmarkScheduler interface that sets the CPU
affinity mask for the current process and gets a benchmark core for use
by llvm-exegesis. This patch additional introduces a BenchmarkScheduler
implementation that simply does nothing, which will preserve the
behavior that we have currently where we do not explicitly set CPU
masks.

Pull Request: google#270

gematria/datasets/pipelines/BUILD.bazel

@@ -81,3 +81,17 @@ gematria_py_test(
         "//gematria/proto:execution_annotation_py_pb2",
     ],
 )
+
+gematria_py_library(
+    name = "benchmark_cpu_scheduler",
+    srcs = ["benchmark_cpu_scheduler.py"],
+)
+
+gematria_py_test(
+    name = "benchmark_cpu_scheduler_test",
+    size = "small",
+    srcs = ["benchmark_cpu_scheduler_test.py"],
+    deps = [
+        ":benchmark_cpu_scheduler",
+    ],
+)

gematria/datasets/pipelines/benchmark_cpu_scheduler.py

@@ -0,0 +1,68 @@
+# Copyright 2024 Google Inc.
+#
+# 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 abc
+import typing_extensions
+
+
+class BenchmarkScheduler(metaclass=abc.ABCMeta):
+  """Schedules a benchmark and the parent process to reduce noise.
+
+  BenchmarkScheduler is an abstraction that provides two main pieces of
+  functionality. Firstly, it provides a function
+  (setup_and_get_benchmark_core) that allows an implementation to perform any
+  necessary setup in the parent process and provide a core ID that should be
+  used to perform any benchmarking. Additionally, implementations are
+  intended to hold state to verify that the expected state is maintained and
+  not changed by external software.
+  """
+
+  @abc.abstractmethod
+  def setup_and_get_benchmark_core(self) -> int | None:
+    """Sets up the parent process and chooses a benchmark core.
+
+    This function will perform any relevant setup in the parent process,
+    and return a core ID that can be used to run benchmarks on.
+
+    Returns:
+      Returns an integer core ID to specify a core that should be used for
+      running benchmarks, or None to indicate that any core can be used.
+    """
+
+  @abc.abstractmethod
+  def verify(self):
+    """Verifies that conditions match what is expected.
+
+    This function allows for implementations to verify that the original
+    setup created in setup_and_get_benchmark_core is maintained for every
+    benchmark that is run.
+    """
+
+
+class NoSchedulingBenchmarkScheduler(BenchmarkScheduler):
+  """A basic BenchmarkScheduler implementation that does nothing.
+
+  This BenchmarkScheduler implementation does nothing. It leaves scheduling
+  of the benchmarking process to the operating system by specifying any core
+  can be used for benchmarking, performs no setup in the parent process, and
+  performs no verification.
+  """
+
+  @typing_extensions.override
+  def setup_and_get_benchmark_core(self) -> int | None:
+    return None
+
+  @typing_extensions.override
+  def verify(self):
+    pass

gematria/datasets/pipelines/benchmark_cpu_scheduler_test.py

@@ -0,0 +1,29 @@
+# Copyright 2024 Google Inc.
+#
+# 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.
+
+from absl.testing import absltest
+
+from gematria.datasets.pipelines import benchmark_cpu_scheduler
+
+
+class BenchmarkSchedulerTests(absltest.TestCase):
+
+  def test_no_scheduling(self):
+    scheduler = benchmark_cpu_scheduler.NoSchedulingBenchmarkScheduler()
+    self.assertIsNone(scheduler.setup_and_get_benchmark_core())
+    scheduler.verify()
+
+
+if __name__ == '__main__':
+  absltest.main()