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SubjectRe: pageable page tables
On Tue, 25 Nov 1997, Ralf Baechle wrote:

> On Tue, Nov 25, 1997 at 09:37:00PM +0100, Rik van Riel wrote:
>
> > Another concern is that users can grab _all_ of system memory
> > by having several processes do a 2GB mmap of /dev/zero...
> > This 'doesn't take any memory' so they can take up as much
> > (non-pageable) pagetable memory as they want.
> > In fact, this is the main reason people asked me if I could look
> > into this... This is one of the biggest denial-of-service holes
> > still left. (ssstt)
>
> So the resource accounting should count those pages also.

That's not the point, as long as page-tables can't be swapped
out, they will take up memory. Users sometimes have a memory
quota as large as all of physical memory, which doesn't matter
when things get swapped out. But when they take up memory by
mmapping /dev/zero, their memory usage is completely _unswappable_

grtz,


Rik.

----------
Send Linux memory-management wishes to me: I'm currently looking
for something to hack...


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