[Zope-dev] zope.interface memory optimization

[Brian Sutherland]

On Wed, Nov 10, 2010 at 12:07:00PM +0100, Charlie Clark wrote:
> Am 10.11.2010, 01:40 Uhr, schrieb Brian Sutherland  
> <brian at vanguardistas.net>:
> 
> >> > On the micro benchmarks, the only difference I see is a memory
> >> > improvement which I think will not survive in practice because most
> >>
> >> ... ?
> > Er, somehow my thoughts didn't make it into text:
> > attributes are zope.schema fields (i.e. subclasses of Attribute).
> > To really make that work, you'd have to add __slots__ to most of the
> > classes in zope.schema as well.
> 
> It might be purely academic but if this does significantly reduce memory  
> use then it might be worth pursuing.

Turns out it's not that academic. I tried a bit harder and managed to
apply __slots__ to the Element, Attribute and Method classes in
zope.interface. That saved an additional 0.5 % of memory (bytes).

I have a small patch to zope.schema that fixes the breakage there.

It looks like there is an additional 0.5% available if zope.schema is
refactored to use slots as well.

> Slots are supposed to be beneficial  
> when you've got lots of objects around. Zope schema fields are pretty  
> static anyway so I don't see a great penalty in having to add slots to  
> them, although obviously a migration of a larger project would probably be  
> a pain.

Searching for __dict__ here:

    http://zope3.pov.lt/trac/browser/zope.schema/trunk/src/zope/schema/_bootstrapfields.py

Will give you a good idea of the problems. Field.bind and
ValidatedProperty both depend heavily on __dict__.

For ValidatedProperty in particular I have no idea how that would work
when using slots.

> Back to the micro-optimisation. At Jeff Rush's talk at PyCon this year he  
> covered the penalties incurred by "." lookups so that might be something  
> that could be investigated but might it also be possible to "memoize" the  
> method calls? I keep forgetting when you can't do that.

I had a look at http://en.wikipedia.org/wiki/Memoization, but I don't
see how it could be applied in this case.

> Charlie
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> Charlie Clark
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-- 
Brian Sutherland