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Title: regrtest: run tests in subprocesses with -j1 on buildbots
Type: Stage:
Components: Tests Versions: Python 3.6
Status: closed Resolution: fixed
Dependencies: Superseder:
Assigned To: Nosy List: Arfrever, vstinner
Priority: normal Keywords: patch

Created on 2015-09-30 20:36 by vstinner, last changed 2022-04-11 14:58 by admin. This issue is now closed.

File name Uploaded Description Edit
regrtest_run_in_subprocess.patch vstinner, 2015-09-30 20:36 review
Messages (2)
msg251962 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2015-09-30 20:36
Currently, regrtest ignores the -j1 parameter. For -jN, the multiprocess mode is only enabled for N != 1. I propose to modify regrtest to run tests in subprocesses when -j1 is used. It would solve the issue #18906.

I also want to run tests in subprocesses in buildbot to better isolate tests. Running all tests in the same process, sequentially, cause various issues:

* various kinds of side effects
* memory leaks
* random failures (unreliable tests)

"make buildbot" already runs regrtest with -j1. I propose to also modify Tools/buildbot/test.bat to use run tests with -j1 by default on Windows.

I fixed regrtest to setup tests using the same code for classic mode and multiprocess mode: slaves (child processes running tests for regrtest -jN) now inherit
--memlimit/-M, --threshold/-t and --nowindows/-n options.

Only 3 remaining functions are incompatible with -jN: --coverage/-T and --findleaks/-l.

Finally, the multiprocess mode of regrtest now displays the duration of tests which took longer than 30 seconds, and every minute, it displays the tests running since longer than 30 seconds. Example with multiple workers (-j4):
[395/399/1] test_mimetypes -- running: test_lzma (111 sec), test_multiprocessing_forkserver (224 sec)
[396/399/1] test_poplib -- running: test_lzma (111 sec), test_multiprocessing_forkserver (225 sec)
[397/399/1] test_lzma (111 sec) -- running: test_multiprocessing_forkserver (225 sec)
[398/399/1] test_range -- running: test_multiprocessing_forkserver (227 sec)
running: test_multiprocessing_forkserver (287 sec)
[399/399/1] test_multiprocessing_forkserver (340 sec)
378 tests OK.

Note: "python -m test -j1 -j4" uses 4 workers, only the last -jN parameter is used. Some buildbots add -jN to use more workers.
msg265936 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2016-05-20 11:42
changeset:   101449:6f7e5b51c8fb
user:        Victor Stinner <>
date:        Fri May 20 13:15:55 2016 +0200
files:       Lib/test/libregrtest/ Misc/NEWS Tools/buildbot/test.bat
regrtest doesn't ignore -j1 anymore

* regrtest now uses subprocesses when the -j1 command line option
  is used: each test file runs in a fresh child process. Before, the -j1 option
  was ignored.
* Tools/buildbot/test.bat script now uses -j1 by default to run
  each test file in fresh child process.
Date User Action Args
2022-04-11 14:58:22adminsetgithub: 69472
2016-05-20 11:42:12vstinnersetstatus: open -> closed
resolution: fixed
messages: + msg265936
2015-10-12 12:21:48Arfreversetnosy: + Arfrever
2015-09-30 20:36:29vstinnersetfiles: + regrtest_run_in_subprocess.patch
keywords: + patch
2015-09-30 20:36:02vstinnercreate