On Wed, Nov 18, 2009 at 11:48 PM, Dominic LoBue <[email protected]> wrote:
> Ian,
>
> I had not yet done any testing when I emailed you that patch originally.
>
> When I did some testing the other day in order to determine what
> difference, if any, the __slots__ attribute made, the results were
> surprising. My application using the __slots__ patched version of
> urwid used 4-5 megs more ram than the unpatched version.
>
> I am not totally sure why this is; as I explained before, the
> __slots__ attribute reduces an object's memory footprint by changing
> the data structure of attributes from a dict to a tuple. My first
> thought is that it may be from pre-allocating the memory space for the
> _urwid_signals attribute on every object for the new way you're doing
> signals, and that pre-allocation on every widget eliminates any
> previous gains.
>
> Switching signals back to the previous implementation may solve the problem.
>
> As for my testing methodology, I loaded up the mail program I've been
> developing using Urwid and loaded all conversations in my email. Doing
> this loaded ~2650 AttrMap wrapped Text widgets into a Listbox. Once
> all the widgets were loaded I did ps aux in another terminal and
> looked at the RSS field.
>
> My program using an unmodified version of Urwid used ~143000k of ram.
> My program using Urwid with my patch used ~148000k of ram.
>
> Dominic
>
>
> On Wed, Nov 11, 2009 at 5:44 AM, Ian Ward <[email protected]> wrote:
>> Dominic LoBue wrote:
>> > As you suggested when I mentioned including __slots__, I went through
>>> Urwid and added the __slots__ attribute where it made sense.
>>>
>>> Attached is a mercurial export of my changes. I've been using that
>>> code all day today with my program and have worked out most of the
>>> snags. The only problem I'm aware of is with the LineBox widget, I get
>>> this error:
>>> TypeError: Error when calling the metaclass bases
>>> multiple bases have instance lay-out conflict
>>>
>>> I tried looking for a simple fix to get it working, but frankly it
>>> made my brain hurt. >.< I finally gave in and just commented the
>>> widget out since I wasn't using it anyway, and everything else worked.
>>> Maybe you'll have an idea for a fix.
>>
>> I'm unfamiliar with __slots__, but it looks like it would break any kind
>> of multiple inheritance. It also would cause a problem any time you
>> want to add an attribute that wasn't declared.
>>
>> What are the memory footprint gains you are seeing by using __slots__?
>> How are you measuring them?
>>
>> I think they may only be appropriate for some classes, like the canvas
>> classes, and things like AttrSpec that really only ever have a few
>> attributes, and there is no need to subclass them.
>>
>> Ian
>>
>>
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>>
>>
>
Addendum-
Quick example of what I'm talking about dict vs tuple:
In [1]: import sys
In [2]: a = []
In [3]: s = {}
In [4]: d = tuple()
In [5]: sys.getsizeof(a)
Out[5]: 72
In [6]: sys.getsizeof(s)
Out[6]: 280
In [7]: sys.getsizeof(d)
Out[7]: 56
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