STINNER Victor added the comment: Guido van Rossum added the comment: > I've lost some context, but perhaps we should have the notion of > "granularity" of the poll/select timeout (e.g. 1 msec), and consider > events that are in the future by less than that granularity as ready? > Then we can round the timeout down: if someone passes a timeout of 1.1 > msec, poll would wait for approximately 1 msec, and when it returns > the event would be considered "due now" as long as the balance (about > 0.1 msec) was under 1 msec.
Well, it sounds like a good compromise according to my experimentation in my last commits on epoll and selectors. New attached asyncio_granularity.patch: - Restore the previous rounding method for poll and epoll (in select and selectors modules), remove unit tests which were designed to test the rounding the timeout away from zero - Add a new resolution attribute to selectors.BaseSelector (select: 1e-6, poll and epoll: 1e-3, kqueue: 1e-9) - Add a new granularity attribute to asyncio.BaseEventLoop: maximum of time resolution and selector resolution - Add a unit test for asyncio counting the number of calls to _run_once(), independent of the selector and the platform - BaseEventLoop._run_once() rounds the deadline and current time using granularity I tested the patch on Linux, FreeBSD and Windows (select, selectors and asyncio tests pass). Granularity: - Linux. poll, epoll: 1 ms, select: 1 us (resolution of time.monotonic: 1 ns) - FreeBSD. poll: 1 ms, select: 1 us, kqueue: 11 ns (resolution of time.monotonic: 11 ns) - Windows (tested on my Windows 7 VM): select, proactor: 15.6 ms (resolution of time.monotonic(): 15.6 ms) BaseProactorEventLoop doesn't use the resolution of IocpProactor because I don't know the resolution :-) Anyway, time.monotonic() has a low resolution (15.6 ms) and so it should be fine. If the patch is accepted, my changes on Python 3.3 should also be reverted. ---------- Added file: http://bugs.python.org/file33680/asyncio_granularity.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue20311> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
