[Vm-dev] oops to zero

Keith Hodges keith_hodges at yahoo.co.uk
Fri Oct 5 03:05:52 UTC 2007

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?

Since OLPC applications have a virtual linux box to themselves can we 
just pick a number that suits us/them?
> Otherwise
> the computational energy used to traverse the image is technically 
> wasted.
> (c) ittle/big endian?  OLPC is based on the geod aka intel instruction 
> set.
So it looks like little-endian is the favoured choice for the normalized 
> http://wiki.laptop.org/go/Hardware_specification
best regards


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