"""This file benchmarks GC collection time for a large number of tiny

dataclass-like instances.

For each type, the following is measured:

- Time for a single full GC pass over all the data.

- Amount of memory used to hold all the data

"""

import gc

import sys

import time

import msgspec

def sizeof(x, _seen=None):

"""Get the recursive sizeof for an object (memoized).

Not generic, works on types used in this benchmark.

"""

if _seen is None:

_seen = set()

_id = id(x)

if _id in _seen:

return 0

_seen.add(_id)

size = sys.getsizeof(x)

if isinstance(x, dict):

for k, v in x.items():

size += sizeof(k, _seen)

size += sizeof(v, _seen)

if hasattr(x, "__dict__"):

size += sizeof(x.__dict__, _seen)

if hasattr(x, "__slots__"):

for k in x.__slots__:

size += sizeof(k, _seen)

size += sizeof(getattr(x, k), _seen)

return size

class Point(msgspec.Struct):

x: int

y: int

z: int

class PointGCFalse(msgspec.Struct, gc=False):

x: int

y: int

z: int

class PointClass:

def __init__(self, x, y, z):

self.x = x

self.y = y

self.z = z

class PointClassSlots:

__slots__ = ("x", "y", "z")

def __init__(self, x, y, z):

self.x = x

self.y = y

self.z = z

def bench_gc(cls):

# Allocate a dict of structs

data = {i: cls(i, i, i) for i in range(1_000_000)}

# Run a full collection

start = time.perf_counter()

gc.collect()

stop = time.perf_counter()

gc_time = (stop - start) * 1e3

mibytes = sizeof(data) / (2**20)

return gc_time, mibytes

def format_table(results):

columns = ("", "GC time (ms)", "Memory Used (MiB)")

rows = []

for name, t, mem in results:

rows.append((f"**{name}**", f"{t:.2f}", f"{mem:.2f}"))

widths = tuple(max(max(map(len, x)), len(c)) for x, c in zip(zip(*rows), columns))

row_template = ("|" + (" %%-%ds |" * len(columns))) % widths

header = row_template % tuple(columns)

bar_underline = "+%s+" % "+".join("=" * (w + 2) for w in widths)

bar = "+%s+" % "+".join("-" * (w + 2) for w in widths)

parts = [bar, header, bar_underline]

for r in rows:

parts.append(row_template % r)

parts.append(bar)

return "\n".join(parts)

def main():

results = []

for name, cls in [

("standard class", PointClass),

("standard class with __slots__", PointClassSlots),

("msgspec struct", Point),

("msgspec struct with gc=False", PointGCFalse),

]:

print(f"Benchmarking {name}...")

gc_time, mibytes = bench_gc(cls)

results.append((name, gc_time, mibytes))

print(format_table(results))

if __name__ == "__main__":

main()