> Did I get that right - does your image only grow by 11% with 
> these changes? Eh, I thought that all that "compact classes 
> stuff" had a larger impact than that.

I belive so...note this is not the stock VM...but I would assume a
similar distribution of object header types.  As an outside estimate,
you can calculate what adding 4 bytes to *every* object in memory would
do by inspecting the result of this (note this will save your image):

| objCount imageSize |
Smalltalk snapshot: true andQuit: false.
imageSize := (FileStream oldFileNamed: (Smalltalk imageName)) size.
objCount := 0.
Smalltalk allObjectsDo: [ :ea | objCount := objCount + 1].
(((objCount * 4) / imageSize) * 100) asFloat.

The result is the percentage increase in object memory size...I get
about 9.5% when evaluating this code.  This means that even if 4 bytes
were added to every object, the image size would increase by 9.5%.

> So... why do we bother with them (and the small hash) at all? 
> Or am I missing something? I do agree that we should try to 
> keep things "small" but 11% sounds like small fish compared 
> to other savings that could be made simply by cleaning up 
> Squeak code...

To fit on machines where every bit counts I guess.  But, on today's
laptops and desktops, it really is small fish (2MB added to my image).

- Stephen


> -----Original Message-----
> From: squeak-dev-admin at lists.squeakfoundation.org 
> [mailto:squeak-dev-admin at lists.squeakfoundation.org] On 
> Behalf Of goran.hultgren at bluefish.se
> Sent: Monday, August 19, 2002 3:46 PM
> To: squeak-dev at lists.squeakfoundation.org
> Subject: Re: Persistence VM?
> 
> 
> "Stephen Pair" <spair at acm.org> wrote:
> [SNIP of a lot of stuff]
> > An analysis of my current working image (which has 623,385 
> objects in
> > it) indicates that such changes in the object memory layout will 
> > result in about an 11% increase the amount of memory needed 
> for this 
> > set of objects (about 78% of the objects in my image are small and 
> > compact, another 4.4% are large)
> 
> Did I get that right - does your image only grow by 11% with 
> these changes? Eh, I thought that all that "compact classes 
> stuff" had a larger impact than that.
> 
> So... why do we bother with them (and the small hash) at all? 
> Or am I missing something? I do agree that we should try to 
> keep things "small" but 11% sounds like small fish compared 
> to other savings that could be made simply by cleaning up 
> Squeak code...
> 
> Note: I am way out of my depths here - please feel free to correct me.
> 
> regards, Göran
> 
>