[squeak-dev] Re: Splitting Object Memory

Bert Freudenberg bert at freudenbergs.de
Tue Nov 17 17:07:19 UTC 2009


On 17.11.2009, at 17:07, Jon Hylands wrote:

> On Tue, 17 Nov 2009 12:52:28 +0100, Bert Freudenberg
> <bert at freudenbergs.de> wrote:
> 
>> I'd love to have even a simple version of this. E.g., split the image into just two parts. Sort-of like VW's perm space (which is not garbage-collected ever) which would be the "base-image", plus all the rest in a second image file. This would allow to share a base image and a differential image in a similar fashion as we have a sources and a changes file. A regular save would just save the non-permanent part of the object memory. 
> 
> The other thing this would buy us is the ability to do FLASH-memory
> based devices. Those objects (and of course that includes code) that
> are "permanent" can be in PermSpace, which physically sits in FLASH.
> 
> Later,
> Jon

That would require a segmented object memory, right?

I thought of it as being loaded into a contiguous region of memory - same as now. A simple oop comparison would suffice to determine if we're in perm space, just like the oldspace check works now. Basically, GC would simply start at the top of perm space. Not sure how to deal with stores into old space though, and I guess "outpointers" are needed too. But then, there are people more familiar with Object Memory design around here ;)

- Bert -




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