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SubjectRe: [2.4.26] overcommit_memory documentation clarification
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.
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