Original from  Mike Bilow  to Denis Tonn on 06-05-1996
Original Subject: Toolkit 1.3 from Devcon

                         ---------------------------------------

  DT>  It looks like under Warp GA it was still possible to
  DT> "commit" the "nothing" addresses between the first and
  DT> second page (using  DosSetMem).
  DT>  After Connect, it is now impossible. The addresses are
  DT> "nothing" and will stay that way. Connect has closed a
  DT> "hole". 
 
MB> As far as I know, Mario's quote from the docs is just plain wrong.  The 
MB> allocation of memory results in some kind of selector being 
MB> mapped, and that selector will have whatever length is 
MB> appropriate for the allocation, subject to 4 KB 
MB> granularity.  That is, if 1 byte is allocated, then the 
MB> selector is mapped to a 4 KB area of memory.  You cannot 
MB> then call DosSetMem() to commit more memory than the 
MB> allocated selector length under any version of OS/2.

 Hmm.. I have allocated an address range without commit, then 
committed the pages one at a time. The tiled selector was automaticly 
adjusted in it's limit after each commit. It has to do this for 16/32 
code compatability (the reason for the tiled selector in the LDT). 

 I never tried to do what I suspect the documentation is saying, IE: 
allocate a 4K page and then commit additional pages beyond the 
original allocation size. It will take some testing to prove it one 
way or another. 

 If you are interested, selector 7 is a readonly selector to the 
base address of the LDT, and if you map this address into a LDT struc
then you can "watch" the tiling process take place. 
 


   Denis       

 Certified OS/2 Engineer, Certified OS/2 Instructor, Certifiable....
 All opinions are my very own, IBM has no claim upon them
 
.
--- Maximus/2 3.01