Memory usage grow on task switching

[pohmelie]

import asyncio

from PyQt5 import QtWidgets
from quamash import QEventLoop


@asyncio.coroutine
def Switcher():

    while True:

        yield from asyncio.sleep(0.001)


if __name__ == "__main__":

    import sys

    app = QtWidgets.QApplication(sys.argv)
    loop = QEventLoop(app)
    asyncio.set_event_loop(loop)

    with loop:

        loop.run_until_complete(Switcher())

Usage grow proportinally to switching speed. I made some big app with awesome 👍 quamash, and saw slow growing for hours of work.

Tested with:

• Ubuntu 14.04 / Python 3.4.3 / PyQt 5.5
• Windows 7 / Python 3.5.0 / PyQt 5.5.1
• Windows xp / Python 3.4.4 / PyQt 5.5

[harvimt]

Looks like the QApplication object keeps a reference to the QTimer objects.

I'm not sure what to do about this. We could re-user the QTimer objects, but it still seems like a good idea to be able to destroy them.

There's some discussion on these issues here: http://enki-editor.org/2014/08/23/Pyqt_mem_mgmt.html

I may have to subclass or wrap QTimer in some way so we're not using a closure as a slot. (or we may have to use QBasicTimer instead of QTimer

[harvimt]

I looks like migrating to QBasicTimer is probably a good idea anyway, but it'll require some pretty serious refactoring.

[harvimt]

I've pushed https://github.com/harvimt/quamash/tree/gh62 which has pretty much the minimum code needed to fix this, but it seems kind of fugly. (like _SimpleTimer and cancellable should be changed, and maybe simple timer should be a factory function that takes in a QtCore like make_signaller does?)

[pohmelie]

I'm glad that you find the problem. Your patch works just fine in place of memory usage. That's great! There is some problem, when I make KeyboardInterrupt (ctrl-c) the test code above. I have infinite logging:

Traceback (most recent call last):
  File "/home/broomrider/tmp/quamash/quamash/__init__.py", line 191, in timerEvent
    self.callback()
  File "/home/broomrider/tmp/quamash/quamash/__init__.py", line 332, in upon_timeout
    assert timer in self.__timers, 'Timer {} not among {}'.format(timer, self.__timers)
AssertionError: Timer None not among []

But that is minor problem, hope for master tree update soon 👏

[harvimt]

try now, I changed that from an assertion to a warning.

[pohmelie]

I think this can be closed since now 👍