Re: SWAP_MAP_MAX: How?

["Stephen C. Tweedie" <sct@redhat.com>]

Hi,

On Fri, Aug 24, 2001 at 01:42:59PM +0100, Hugh Dickins wrote:

> Doesn't it need an anonymous page mapped multiple (e.g. 256) times
> into multiple (e.g. 256) mms to reach the limit?

That would do it, yes.

> And there's an obvious
> way that can happen, by multiply attaching a piece of IPC Shared Memory,
> and multiply forking.  But in that case it's the shared memory object
> which gets the large number of references, and the swap counts stay 1.

Indeed --- sysV shm swapping is eccentric. :-)

There _was_ once a way to do this --- mmap()ing another process's
/proc/*/mem would allow you to get a swap page mapped into memory
multiple times, but we removed support for that way back in pre-2.2
days.  I don't think we allow that any more, unless it's been
reenabled again.

Cheers,
 Stephen
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