On 11:02 pm, na...@animats.com wrote:
I know there's a performance penalty for running Python on a
multicore CPU, but how bad is it? I've read the key paper
("www.dabeaz.com/python/GIL.pdf"), of course. It would be adequate
if the GIL just limited Python to running on one CPU at a time,
but it's worse than that; there's excessive overhead due to
a lame locking implementation. Running CPU-bound multithreaded
code on a dual-core CPU runs HALF AS FAST as on a single-core
CPU, according to Beasley.
It's not clear that Beasley's performance numbers apply to any platform
except OS X, which has a particularly poor implementation of the
threading primitives CPython uses to implement the GIL.
You should check to see if it actually applies to your deployment
environment.
The GIL has been re-implemented recently. Python 3.2, I think, will
include the new implementation, which should bring OS X performance up
to the level of other platforms. It may also improve certain other
aspects of thread switching.
Jean-Paul
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