[MLton-devel] D2 problem

[Henry Cejtin]

The  thing  worrying  me  about  GC  slowing down with multiple chunks is any
things like  tests  for  from/to  space,  which  now  are  considerably  more
expensive.   Also some allocations will fail (because of chunk full) but will
not trigger a GC, but instead put the data in a  different  chunk.   If  this
happens much (10 meg chunks and 1 gig of semi-space would mean only 100 times
per GC) then it will slow things down.  Also you have to decide  what  to  do
after  you  allocate  the `big' object.  Stick to the same chunk (and trigger
this more frequently until we switch chunks) or switch now and waste all  the
remaining space in this chunk.

As  to  the mmap under Cygwin stuff, I'm remembering Linux 2.2 (or maybe 2.0)
where by specifying a non-zero first arg you would cause the  kernel  to  get
the  space  from  a different part of your address space, and that this would
cause you to be able to get more  memory.   The  same  could  be  true  under
Cygwin,  so that there is a way to get more than 2 gig, but just not 2 (or 1)
continuous gig.

You  didn't  answer how important it is to the Polyspace people to be able to
run these big (> 2 gig combined spaces)  programs  under  Windows.   Sadly  I
would guess rather important.

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