threading.py -> winthreading.c : Some results
tim.one at home.com
Tue Jan 1 23:02:41 EST 2002
[posted & mailed]
> I've reimplemented the synchronization objects of threading.py
> in non-portable, Win32-only C.
Sorry I haven't had time to follow up on this -- it's interesting and I want
to encourage you (so I don't have to do it later <wink>).
> The C versions of RLock, Event, Semaphore, and Condition perform
> at least 5x faster than their standard counterparts in threading.py
> in every situation I've tried. Acquiring an RLock runs 25x faster.
> Condition.wait(timeout) runs 500x faster.
> This benchmark:
> runs 6.3 times as fast under the C version of Condition.
> That's fast enough to post a reasonably non-humiliating benchmark
> number; it closes the gap between Python and Java considerably.
> ...If you care about such things. ...As of course no sane person
> Whether this C code would mean a significant performance increase
> in a real-life program remains to be proven. Comments?
It depends on the program, of course.
You could also consider solving a simpler problem, which would definitely
increase performance of real-life programs: "Python locks" are also used
internally by Python, most notoriously for the global interpreter lock. A
Python lock has the unusual property that it's neither "owned" nor
reentrant: any thread can release a Python lock, whether or not it was the
thread that acquired it. And it's legit for any thread to try to acquire a
Python lock, even if the thread has already acquired it (and in that case,
the thread blocks until some other thread releases the lock -- the point is
that this is defined and reliable behavior of a Python lock, but of few
other flavors of lock).
However, Python's internal uses of locks-- and particularly the GIL --don't
need these unusual (relative to what platforms usually offer in the way of
native synch gimmicks) semantics. The GIL is "owned": a thread T that
acquires the GIL won't try to acquire it again while it's acquired, T will
eventually release it itself, and no other thread will attempt to release it
while T has it held. Most platforms have a more efficient synch
implementation for this simple usage, but we never got around to creating an
internal lock type to exploit this. Just about *any* mutex gimmick would
suffice except for a spin lock (the GIL can be held by a thread for an
arbitrarily long time): the GIL exists solely to enforce serialization.
c'mon-you've-been-working-on-this-for-a-year-already<wink>-ly y'rs - tim
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