python performance on Solaris

[Antoine Pitrou]

Le Wed, 14 Oct 2009 22:39:14 -0700, John Nagle a écrit :
> 
>     Note that multithreaded compute-bound Python programs really suck
> on multiprocessors.  Adding a second CPU makes the program go slower,
> due to a lame mechanism for resolving conflicts over the global
> interpreter lock.

I'm not sure what you're talking about. Python has no "mechanism for 
resolving conflicts over the global interpreter lock" (let alone a lame 
one :-)), it just trusts the OS to schedule a thread only when it is not 
waiting on an unavailable resource (a lock). The GIL is just an OS-level 
synchronization primitive and its behaviour (fairness, performance) will 
depend on the behaviour of the underlying OS.

If this belief is derived from Dave Beazley's slides (*) about Python's 
multi-threading issues, I'd say some of his observations are rather 
questionable. First because the measurements were done on OS X, which has 
its own serious concurrency problems (**). Second because one of the 
benchmarks is so synthetic that it doesn't reflect real-world use of 
Python at all.

This is not to say there aren't any issues, of course.


(*) http://www.dabeaz.com/python/GIL.pdf

(**) http://www.nabble.com/Mutex-performance-td24892454.html