19.0 vanilla

odoo-bringout-oca-ocb-base/odoo/tools/gc.py

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+""" Garbage collector tools
+
+## Reference
+https://github.com/python/cpython/blob/main/InternalDocs/garbage_collector.md
+
+## TLDR cpython
+
+Objects have reference counts, but we need garbage collection for cyclic
+references.  All allocated objects are split into collections (aka generations).
+There is also one permanent generation that is never collected (see
+``gc.freeze``).
+
+The GC is triggered by the number of created objects. For the first collection,
+at every allocation and deallocation, a counter is respectively increased and
+decreased. Once it reaches a threshold, that collection is automatically
+collected. Other thresolds indicate that every X collections, the next
+collection is collected.
+
+Default thresolds are 700, 10, 10.
+"""
+import contextlib
+import gc
+import logging
+from time import thread_time_ns as _gc_time
+
+_logger = logging.getLogger('gc')
+_gc_start: int = 0
+_gc_init_stats = gc.get_stats()
+_gc_timings = [0, 0, 0]
+
+
+def _to_ms(ns):
+    return round(ns / 1_000_000, 2)
+
+
+def _timing_gc_callback(event, info):
+    """Called before and after each run of the gc, see gc_set_timing."""
+    global _gc_start  # noqa: PLW0603
+    gen = info['generation']
+    if event == 'start':
+        _gc_start = _gc_time()
+        if gen == 2 and _logger.isEnabledFor(logging.DEBUG):
+            _logger.debug("info %s, starting collection of gen2", gc_info())
+    else:
+        timing = _gc_time() - _gc_start
+        _gc_timings[gen] += timing
+        _gc_start = 0
+        if gen > 0:
+            _logger.debug("collected %s in %.2fms", info, _to_ms(timing))
+
+
+def gc_set_timing(*, enable: bool):
+    """Enable or disable timing callback.
+
+    This collects information about how much time is spent by the GC.
+    It logs GC times (at debug level) for collections bigger than 0.
+    The overhead is under a microsecond.
+    """
+    if _timing_gc_callback in gc.callbacks:
+        if enable:
+            return
+        gc.callbacks.remove(_timing_gc_callback)
+    elif enable:
+        global _gc_init_stats, _gc_timings  # noqa: PLW0603
+        _gc_init_stats = gc.get_stats()
+        _gc_timings = [0, 0, 0]
+        gc.callbacks.append(_timing_gc_callback)
+
+
+def gc_info():
+    """Return a dict with stats about the garbage collector."""
+    stats = gc.get_stats()
+    times = []
+    cumulative_time = sum(_gc_timings) or 1
+    for info, info_init, time in zip(stats, _gc_init_stats, _gc_timings):
+        count = info['collections'] - info_init['collections']
+        times.append({
+            'avg_time': time // count if count > 0 else 0,
+            'time': _to_ms(time),
+            'pct': round(time / cumulative_time, 3)
+        })
+    return {
+        'cumulative_time': _to_ms(cumulative_time),
+        'time': times if _timing_gc_callback in gc.callbacks else (),
+        'count': stats,
+        'thresholds': (gc.get_count(), gc.get_threshold()),
+    }
+
+
+@contextlib.contextmanager
+def disabling_gc():
+    """Disable gc in the context manager."""
+    if not gc.isenabled():
+        yield False
+        return
+    gc.disable()
+    _logger.debug('disabled, counts %s', gc.get_count())
+    yield True
+    counts = gc.get_count()
+    gc.enable()
+    _logger.debug('enabled, counts %s', counts)