David Beazley <d...@dabeaz.com> added the comment:
I've attached a test "fair.py" that gives an example of the fair CPU scheduling
issue. In this test, there are two threads, one of which has fast-running
ticks, one of which has slow-running ticks.
Here is their sequential performance (OS-X, Python 2.6):
slow: 5.71
fast: 0.32
Here is their threaded performance (OS-X, Python 2.6.4):
slow : 5.99
fast : 6.04 (Notice : Huge jump in execution, unfair CPU)
Here is their threaded performance using the Py3K New GIL:
slow : 5.96
fast : 0.67 (Notice : Fair CPU use--time only doubled)
Using Linux with semaphores gives no benefit here. The fast code is stalled in
the same way. For example: here are my Linux results (Ubuntu 8.10,
Python-2.6.4, dual-core, using semaphores):
Sequential:
slow : 6.24
fast : 0.59
Threaded:
slow : 6.40
fast : 6.69 (even slower than the slow code!)
----------
Added file: http://bugs.python.org/file16946/fair.py
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<http://bugs.python.org/issue8299>
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