Re: [2.4.26] overcommit_memory documentation clarification

[Marcelo Tosatti <marcelo.tosatti@cyclades.com>]

On Sun, May 09, 2004 at 11:49:41PM +0200, Vincent Lefevre wrote:
> On 2004-05-09 14:06:11 -0700, Paul Jackson wrote:
> > Vincent wrote:
> > > NULL == (void *) 0 and NULL == 0 must be true
> > Yes - NULL is compares equal to both (void *)0 and 0.
> > No - not necessarily the _same_ value - one could be
> > on a system with 32 bit ints, 64 bit pointers, for example.
> 
> And so?
> 
> > > The goal of malloc is to reserve memory.
> > It's up to the kernel whether sbrk (used by malloc to
> > obtain virtual address space) reserves memory or not.
> 
> More old_mmap than brk (BTW, I forgot to say that this was on
> an x86 machine, I don't know if this matters...).
> 
> > Check out:
> >     /proc/sys/vm/overcommit_memory
> >     Documentation/sysctl/vm.txt - overcommit_memory
> 
> But the documentation is wrong (on an official 2.4.26 kernel).
> It seems that there is no way to get malloc() always return 0
> when there isn't enough memory, even in simple cases (see my
> program posted in the first message).

Right. 

We should or merge Alan's strict-overcommit patches (from RH's tree), 
or fix the documentation.

Marc-Christian Petersen has a patch to fixup the documentation.