[Vm-dev] oops to zero

Bert Freudenberg bert at freudenbergs.de
Fri Oct 5 07:52:16 UTC 2007

On Oct 5, 2007, at 5:05 , Keith Hodges wrote:

> John M McIntosh wrote:
>> (a) The OLPC actually uses a compressed file system already,  
>> because of that Published Sophie Books for the OLPC use a zipped  
>> file with no compression. The zipped file will live in the journal  
>> at some point.
>> (b) Does setting oops values back to start of zero actually make  
>> it more compressable, versus say a start value of 0x00004000?
> We are not actually setting the oops back to zero, but back  
> relative-to-zero, They are just numbers, just different numbers. I  
> would not imagine that this has any effect upon the compressibility  
> of any single image. However diff algorithms working with two or  
> more images are more likely to see that much of a saved image is  
> the same as the last time it was saved. From the little I know it  
> seems that the OLPC file system (as well as mercurial binary  
> storage) is designed with this in mind.
> Indeed you make a good point, if we can pick a good number that  
> runtimes can use without traversing the image then great. What  
> number should it be?

I don't think any OS (except for DOS maybe) would guarantee you a  
specific start address.

> Since OLPC applications have a virtual linux box to themselves can  
> we just pick a number that suits us/them?

I wouldn't think so ... but it is an interesting idea. I will ask the  
OLPC guys.

- Bert -

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