Re: overcommit stuff

[Hugh Dickins <hugh@veritas.com>]

On Sat, 21 Sep 2002, Andrew Morton wrote:
> Hugh Dickins wrote:
> > ...
> > > It seems very unlikely (impossible?) that those pages will
> > > ever become unshared.
> > 
> > I expect it's very unlikely (short of application bugs) that
> > those pages would become unshared; but they have been mapped
> > in such a way that the process is entitled to unshare them,
> > therefore they have been counted.  A good example of why
> > Linux does not impose strict commit accounting, and why
> > you may choose not to use Alan's strict accounting policy.
> 
> OK, thanks.   Just checking.
> 
> Is glibc mapping executables with PROT_WRITE?  If so,
> doesn't that rather devalue the whole overcommit thing?

No, it looks like glibc is doing the right thing (mapping the code
readonly and the data+bss readwrite).  And I was wrong to say it's
unlikely those pages would ever become unshared: the four 0.5MB
areas look like typical readwrite private anon allocations.

Hugh

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/