[Python-Dev] Windows Low Fragementation Heap yields speedup of ~15%

Gfeller Martin Martin.Gfeller at comit.ch
Mon Feb 14 19:41:51 CET 2005

Dear all,

I'm running a large Zope application on a 1x1GHz CPU 1GB mem 
Window XP Prof machine using Zope 2.7.3 and Py 2.3.4 
The application typically builds large lists by appending 
and extending them. 

We regularly observed that using a given functionality a 
second time using the same process was much slower (50%) 
than when it ran the first time after startup. 
This behavior greatly improved with Python 2.3 (thanks 
to the improved Python object allocator, I presume). 

Nevertheless, I tried to convert the heap used by Python 
to a Windows Low Fragmentation Heap (available on XP 
and 2003 Server). This improved the overall run time 
of a typical CPU-intensive report by about 15% 
(overall run time is in the 5 minutes range), with the
same memory consumption.

I consider 15% significant enough to let you know about it.

For information about the Low Fragmentation Heap, see

Best regards,

PS: Since I don't speak C, I used ctypes to convert all 
    heaps in the process to LFH (I don't know how to determine
    which one is the C heap).


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