Add hooks for calling arbitrary code around each benchmark

doc/run_benchmark.rst

@@ -195,9 +195,11 @@ Specializer statistics (``pystats``)
 ==================================
 
 ``pyperf`` has built-in support for `specializer statistics (``pystats``) <https://docs.python.org/dev/using/configure.html#cmdoption-enable-pystats>`_.
-If running benchmarks on a CPython built with the ``--enable-pystats`` flag, pyperf will automatically collect ``pystats`` on the benchmark code by calling ``sys._stats_on`` immediately before the benchmark and calling ``sys._stats_off`` immediately after.
+If running benchmarks on a CPython built with the ``--enable-pystats`` flag, when you pass ``--hook pystats``, pyperf will collect ``pystats`` on the benchmark code by calling ``sys._stats_on`` immediately before the benchmark and calling ``sys._stats_off`` immediately after.
 Stats are not collected when running ``pyperf``'s own code or when warming up or calibrating the benchmarks.
 
+**New in 2.8.0:** The ``--hook pystats`` flag must be given to collect pystats.
+
 Due to the overhead of collecting the statistics, the timing results will be meaningless.
 
 The `Tools/scripts/summarize_stats.py <https://github.com/python/cpython/blob/main/Tools/scripts/summarize_stats.py>`_ script can be used to summarize the statistics in a human-readable form.

pyperf/_collect_metadata.py

@@ -125,10 +125,6 @@ def collect_python_metadata(metadata):
         if not gc.isenabled():
             metadata['python_gc'] = 'disabled'
 
-    # pystats enabled?
-    if hasattr(sys, "_stats_clear"):
-        metadata['pystats'] = 'enabled'
-
 
 def read_proc(path):
     path = proc_path(path)

pyperf/_hooks.py

@@ -0,0 +1,97 @@
+# Hooks are installable context managers defined as entry points so that
+# arbitrary code can by run right before and after the actual internal
+# benchmarking code is run.
+
+
+import abc
+import importlib.metadata
+import sys
+
+
+def get_hooks():
+    hook_prefix = "pyperf.hook"
+    entry_points = importlib.metadata.entry_points()
+    if sys.version_info[:2] < (3, 10):
+        group = entry_points[hook_prefix]
+    else:
+        group = entry_points.select(group=hook_prefix)
+    return (x.load() for x in group)
+
+
+def get_hook_names():
+    return (x.__name__ for x in get_hooks())
+
+
+def get_selected_hooks(hook_names):
+    if hook_names is None:
+        return
+
+    hook_mapping = {hook.__name__: hook for hook in get_hooks()}
+    for hook_name in hook_names:
+        yield hook_mapping[hook_name]
+
+
+class HookError(Exception):
+    pass
+
+
+class HookBase(abc.ABC):
+    def __init__(self):
+        """
+        Create a new instance of the hook.
+        """
+        pass
+
+    def teardown(self, _metadata):
+        """
+        Called when the hook is completed for a process. May add any information
+        collected to the passed-in `metadata` dictionary.
+        """
+        pass
+
+    def __enter__(self):
+        """
+        Called immediately before running benchmark code.
+
+        May be called multiple times per instance.
+        """
+        pass
+
+    def __exit__(self, _exc_type, _exc_value, _traceback):
+        """
+        Called immediately after running benchmark code.
+        """
+        pass
+
+
+class _test_hook(HookBase):
+    def __init__(self):
+        self._count = 0
+
+    def teardown(self, metadata):
+        metadata["_test_hook"] = self._count
+
+    def __enter__(self):
+        self._count += 1
+
+    def __exit__(self, _exc_type, _exc_value, _traceback):
+        pass
+
+
+class pystats(HookBase):
+    def __init__(self):
+        if not hasattr(sys, "_pystats_on"):
+            raise HookError(
+                "Can not collect pystats because python was not built with --enable-pystats"
+            )
+        sys._stats_off()
+        sys._stats_clear()
+
+    def teardown(self, metadata):
+        metadata["pystats"] = "enabled"
+
+    def __enter__(self):
+        sys._stats_on()
+
+    def __exit__(self, _exc_type, _exc_value, _traceback):
+        sys._stats_off()

pyperf/_manager.py

@@ -69,6 +69,10 @@ def worker_cmd(self, calibrate_loops, calibrate_warmups, wpipe):
         if args.profile:
             cmd.extend(['--profile', args.profile])
 
+        if args.hook:
+            for hook in args.hook:
+                cmd.extend(['--hook', hook])
+
         if self.runner._add_cmdline_args:
             self.runner._add_cmdline_args(cmd, args)
 

pyperf/_runner.py

@@ -11,6 +11,7 @@
                                get_isolated_cpus, set_cpu_affinity,
                                set_highest_priority)
 from pyperf._formatter import format_timedelta
+from pyperf._hooks import get_hook_names
 from pyperf._utils import (MS_WINDOWS, MAC_OS, abs_executable,
                            WritePipe, get_python_names,
                            merge_profile_stats)
@@ -77,13 +78,6 @@ def __init__(self, values=None, processes=None,
                  program_args=None, add_cmdline_args=None,
                  _argparser=None):
 
-        # Reset the stats collection if running a --enable-pystats build
-        try:
-            sys._stats_off()
-            sys._stats_clear()
-        except AttributeError:
-            pass
-
         # Watchdog: ensure that only once instance of Runner (or a Runner
         # subclass) is created per process to prevent bad surprises
         cls = self.__class__
@@ -248,6 +242,13 @@ def __init__(self, values=None, processes=None,
                             help='Collect profile data using cProfile '
                                  'and output to the given file.')
 
+        hook_names = list(get_hook_names())
+        parser.add_argument(
+            '--hook', nargs="*", choices=hook_names,
+            metavar=f"{', '.join(x for x in hook_names if not x.startswith('_'))}",
+            help='Use the given pyperf hooks'
+        )
+
         memory = parser.add_mutually_exclusive_group()
         memory.add_argument('--tracemalloc', action="store_true",
                             help='Trace memory allocations using tracemalloc')
@@ -732,6 +733,10 @@ def bench_command(self, name, command):
         if self.args.profile:
             command.extend(["--profile", self.args.profile])
 
+        if self.args.hook:
+            for hook in self.args.hook:
+                command.extend(["--hook", hook])
+
         # Use lazy import to limit imports on 'import pyperf'
         from pyperf._command import BenchCommandTask
         task = BenchCommandTask(self, name, command)

pyperf/_worker.py

@@ -1,10 +1,12 @@
+import contextlib
 import statistics
 import sys
 import time
 
 import pyperf
 from pyperf._formatter import (format_number, format_value, format_values,
                                format_timedelta)
+from pyperf._hooks import get_selected_hooks, HookError
 from pyperf._utils import MS_WINDOWS, MAC_OS, percentile, median_abs_dev
 
 
@@ -58,19 +60,14 @@ def _compute_values(self, values, nvalue,
 
         task_func = self.task_func
 
-        # If we are on a pystats build, turn on stats collection around the
-        # actual work, except when calibrating.
-        if hasattr(sys, "_stats_on") and not calibrate_loops:
-            core_task_func = task_func
-
-            def stats_func(*args):
-                sys._stats_on()
-                try:
-                    return core_task_func(*args)
-                finally:
-                    sys._stats_off()
-
-            task_func = stats_func
+        hook_managers = []
+        for hook in get_selected_hooks(args.hook):
+            try:
+                hook_managers.append(hook())
+            except HookError as e:
+                print(f"ERROR setting up hook '{hook.__name__}:'", file=sys.stderr)
+                print(str(e), file=sys.stderr)
+                sys.exit(1)
 
         index = 1
         inner_loops = self.inner_loops
@@ -80,7 +77,11 @@ def stats_func(*args):
             if index > nvalue:
                 break
 
-            raw_value = task_func(self, self.loops)
+            with contextlib.ExitStack() as stack:
+                for hook in hook_managers:
+                    stack.enter_context(hook)
+                raw_value = task_func(self, self.loops)
+
             raw_value = float(raw_value)
             value = raw_value / (self.loops * inner_loops)
 
@@ -116,6 +117,9 @@ def stats_func(*args):
 
             index += 1
 
+        for hook in hook_managers:
+            hook.teardown(self.metadata)
+
     def collect_metadata(self):
         from pyperf._collect_metadata import collect_metadata
         return collect_metadata(process=False)

pyperf/tests/test_perf_cli.py

@@ -719,6 +719,18 @@ def test_command_track_memory(self):
 
         self._check_track_memory_bench(bench, loops=2)
 
+    def test_hook(self):
+        with tests.temporary_file() as tmp_name:
+            self.run_command('timeit',
+                             '--hook',
+                             '_test_hook',
+                             '-p2', '-w1', '-l5', '-n3',
+                             '[1,2]*1000',
+                             '-o', tmp_name)
+            bench = pyperf.Benchmark.load(tmp_name)
+        metadata = bench.get_metadata()
+        assert metadata.get("_test_hook", 0) > 0
+
 
 class TestConvert(BaseTestCase, unittest.TestCase):
     def test_stdout(self):

pyproject.toml

@@ -56,6 +56,10 @@ dev = [
 [project.scripts]
 pyperf = "pyperf.__main__:main"
 
+[project.entry-points."pyperf.hook"]
+pystats = "pyperf._hooks:pystats"
+_test_hook = "pyperf._hooks:_test_hook"
+
 [tool.setuptools]
 packages = ["pyperf", "pyperf.tests"]