malloc does not return null when out of memory

[Matthias Buelow]

Peter Jeremy wrote:

> FreeBSD behaviour in the face of swap shortage is a regular and
> popular discussion topic.  I suggest that a perusal of the archives
> will probably answer any questions.  If anyone wishes to suggest a
> "solution" to FreeBSD's behaviour when there is a shortage of swap,
> please include patches.

What makes me ask the following (note that it's neither a flame, nor a 
suggestion).  Does FreeBSD actually account the used swap/vm so far (it 
needn't since it doesn't guarantee that it'll be available, with 
overcommit) or does it not do that (i.e., it has no idea of how much vm 
was requested by all processes so far, without having to go through the 
maps of all processes, of course)?  And is it planned in the (distant) 
future to add a knob to toggle overcommitting of swap?  While with large 
disks and hence swap sizes this probably isn't a pressing problem for 
most applications, it might be nice to be able to control the system not 
  to randomly kill off applications or force the user to meticulously 
plan and calculate memory load of the planned application zoo in order 
to tune the ulimits of various memory-hungry processes in a way that 
they'll all fit into swap in the worst case situation.

-- 
   Matthias Buelow;  mkb@{mukappabeta.de,informatik.uni-wuerzburg.de}