James Sutherland wrote:
> On Thu, 16 Mar 2000, Paul Jakma wrote:
> > On Thu, 16 Mar 2000, James Sutherland wrote:
> > > On Wed, 15 Mar 2000, Paul Jakma wrote:
> > > That doesn't happen. malloc() ALLOCATES the memory to the process. It is
> > > *NOT* overcommitted. It may be backed by swapspace rather than physical
> > > memory, but that block of memory *IS* available to the process.
> >
> > so malloc() isn't overcommited? malloc()'ed memory is guaranteed to be
> > available - ie the memory is reserved and accounted for at malloc()
> > time?
>
> malloc() CAN be overcommitted. If you set a VM flag via /proc, then
> malloc() will *ALWAYS* succeed, even if there isn't any memory available
> at all. With the flag clear, malloc() does some sanity checking before
> granting the memory.
>
> You CAN obtain an overcommit free malloc() by clearing the VM flag (it is
> clear by default), then touching every page you allocate when you allocate
> it.
No, this will just result in your process SIGBUS'ing. The current
do_mmap (in mmap_fixup) will call make_pages_present(). There's no error
return. It'll just die if one of the pages could not be faulted.
-- John Ripley, empeg Ltd. http://www.empeg.com- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Thu Mar 23 2000 - 21:00:24 EST