I am pretty sure (61%) that in the original release of 2.2.0 there was something about a speed increase. One talked about on single processor (20-40%) and the other was dual processor (60-80%). It partly has to do with that "one line of magic code" in the z2.py.

Ethan? Paul? DC? Care to shed some light?

The speedup involves changing sys.checkinterval, which controls the interval (# of bytecodes) at which the Python runtime performs certain housekeeping chores. For multithreaded programs, upping this interval can cause a significant performance improvement (more about this on python.org in the sys module docs). 2.2 sets the interval to 120, a value that seemed to provide a general speedup across a number of systems I tested. Granted, this is not very scientific, which is why there is an '-i' option to z2.py that allows you to pass your own values for the interval to experiment and find a sweet spot for your given environment (see the z2.py docstring / command help).

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else changed I didnt see? I noticed that 2.1.6 wasnt making the best use of dual processors.

I thought only ZEO would make good use fo dual processors?

Note that effective use of multiple processors is mostly a function of the Python runtime (specifically the global interpreter lock) rather than an issue that Zope can address directly. So yes, ZEO is the best way to make effective use of MP. Brian Lloyd brian@digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com