[Python-Dev] PyDict_SetItem hook

Guido van Rossum guido at python.org
Thu Apr 2 23:19:58 CEST 2009


Wow. Can you possibly be more negative?

2009/4/2 Raymond Hettinger <python at rcn.com>:
> The measurements are just a distractor.  We all already know that the hook
> is being added to a critical path.  Everyone will pay a cost for a feature
> that few people will use.  This is a really bad idea.  It is not part of a
> thorough, thought-out framework of container hooks (something that would
> need a PEP at the very least).    The case for how it helps us is somewhat
> thin.  The case for DTrace hooks was much stronger.
>
> If something does go in, it should be #ifdef'd out by default.  But then, I
> don't think it should go in at all.
>
>
> Raymond
>
>
>
>
> On Thu, Apr 2, 2009 at 04:16, John Ehresman <jpe at wingware.com> wrote:
>>
>> Collin Winter wrote:
>>>
>>> Have you measured the impact on performance?
>>
>> I've tried to test using pystone, but am seeing more differences between
>> runs than there is between python w/ the patch and w/o when there is no hook
>> installed.  The highest pystone is actually from the binary w/ the patch,
>> which I don't really believe unless it's some low level code generation
>> affect.  The cost is one test of a global variable and then a switch to the
>> branch that doesn't call the hooks.
>>
>> I'd be happy to try to come up with better numbers next week after I get
>> home from pycon.
>
> Pystone is pretty much a useless benchmark. If it measures anything, it's
> the speed of the bytecode dispatcher (and it doesn't measure it particularly
> well.) PyBench isn't any better, in my experience. Collin has collected a
> set of reasonable benchmarks for Unladen Swallow, but they still leave a lot
> to be desired. From the discussions at the VM and Language summits before
> PyCon, I don't think anyone else has better benchmarks, though, so I would
> suggest using Unladen Swallow's:
> http://code.google.com/p/unladen-swallow/wiki/Benchmarks
>
>
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--Guido van Rossum (home page: http://www.python.org/~guido/)


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