Title: ProcessPool workers hold onto return value of last task in memory
Type: Stage: patch review
Components: Library (Lib) Versions: Python 3.8
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: bquinlan, dchevell, pitrou
Priority: normal Keywords: patch, patch, patch, patch

Created on 2019-01-11 08:36 by dchevell, last changed 2019-01-13 18:25 by xtreak.

Pull Requests
URL Status Linked Edit
PR 11514 open dchevell, 2019-01-11 08:41
PR 11514 open dchevell, 2019-01-11 08:41
PR 11514 open dchevell, 2019-01-11 08:41
PR 11514 open dchevell, 2019-01-11 08:41
Messages (1)
msg333444 - (view) Author: David Chevell (dchevell) * Date: 2019-01-11 08:36
ProcessPoolExecutor workers will hold onto the return value of their last task in memory until the next task is received. Since the return value has already been propagated to the parent process's `Future` or else effectively discarded, this is holding onto objects unnecessarily.

Simple case to reproduce:

    import concurrent.futures
    import time

    executor = concurrent.futures.ProcessPoolExecutor(max_workers=1)

    def big_val():
        return [{1:1} for i in range(1, 1000000)]


    # Observe the memory usage of the process worker during the sleep interval

This should be easily fixed by having the worker explicitly `del r` after calling `_sendback_result` as it already does this for `call_item`
Date User Action Args
2019-01-13 18:25:56xtreaksetkeywords: patch, patch, patch, patch
nosy: + bquinlan, pitrou
2019-01-11 08:42:00dchevellsetkeywords: + patch
stage: patch review
pull_requests: + pull_request11078
2019-01-11 08:41:56dchevellsetkeywords: + patch
stage: (no value)
pull_requests: + pull_request11077
2019-01-11 08:41:52dchevellsetkeywords: + patch
stage: (no value)
pull_requests: + pull_request11076
2019-01-11 08:41:48dchevellsetkeywords: + patch
stage: (no value)
pull_requests: + pull_request11075
2019-01-11 08:36:21dchevellcreate