[Zope-dev] is threading in zope useful ?

[sathya]

Tim Peters wrote:
tim thanks much for the explanation. some points below.
> [sathya]
> 
>>I read somewhere that each zope thread acquires the global python
>>interpreter lock before processing a request and until it releases it
>>the other zope threads are essentially locked out.
> 
> 
[tim]
> No.  The GIL effectively serializes threads doing pure computation in
> Python, but many pieces of the Python implementation release the GIL around
> calls to known-threadsafe C libraries.  The most important examples of that
> are I/O, of many kinds.  For example, if a Python thread opens a socket, the
> GIL is released around the C-level code that does the low-level socket open,
> which allows other Python threads to proceed in parallel (of course the
> thread that does the C-level socket open waits for the latter to finish; it
> reacquires the GIL after the socket operation is complete and it's ready to
> go back to interpreting Python bytecodes).  Because Zope does a lot of
> network I/O, this form of parallelism can be very useful for it.
> 
[sathya]
great ! If I understand correctly, if we had a zope process running on 
an smp linux machine and doing lots of RDBMS calls we would not be 
limited by the GIL. In essence threads running on multiple cpus would 
probably not have to wait on acquiring the GIL as most every page 
request results in  a ZSQL method call which in turn would release the 
GIL. Therefore SMP may not be hindered by the GIL.
That said , since ZEO ends up doing multiple python interpreters its 
possibly the  more reliable approach to take advantage of SMP linux.
please point out any flaws in my thought process .....

again thanks very much for putting it in persepective. it clears up some
fog for us !

regards
sathya