Created
November 27, 2018 15:53
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Test for behaviour of GC in python multiprocessing using regular/shared objects
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import multiprocessing | |
import time | |
import sys | |
process_identifier = 'main' | |
class Collectible: | |
def __init__(self, identifier): | |
self.identifier = identifier | |
self.collections = multiprocessing.Value('i') | |
def __del__(self): | |
with self.collections.get_lock(): | |
self.collections.value += 1 | |
print('__del__ %r in %s [%d]' % (self.identifier, process_identifier, self.collections.value)) | |
def __repr__(self): | |
return '%s(%s, collections=%d)' % (self.__class__.__name__, self.identifier, self.collections.value) | |
def drop_refs(child_id, payload: Collectible): | |
global process_identifier | |
process_identifier = child_id | |
print('start', child_id, 'payload', payload) | |
time.sleep(0.2) | |
print('drop', child_id) | |
del payload | |
time.sleep(0.2) | |
print('done', child_id) | |
def local_ref(drop_early=False): | |
local_child = Collectible('local') | |
procs = [ | |
multiprocessing.Process(target=drop_refs, args=(i, local_child)) | |
for i in range(4) | |
] | |
print('start children') | |
if drop_early: | |
print('drop main') | |
del local_child | |
for proc in procs: | |
proc.start() | |
for proc in procs: | |
proc.join() | |
print('done all') | |
if __name__ == '__main__': | |
method = sys.argv[1] if len(sys.argv) > 1 else None | |
multiprocessing.set_start_method(method) | |
print('drop late....') | |
local_ref() | |
print('drop early....') | |
local_ref(drop_early=True) |
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