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From
SubjectRe: Interesting VM feature?
Date
Followup to:  <20030815211937.GA20208@mail.jlokier.co.uk>
By author: Jamie Lokier <jamie@shareable.org>
In newsgroup: linux.dev.kernel
>
> Mike Fedyk wrote:
> > On Fri, Aug 15, 2003 at 02:56:02PM -0500, mouschi@wi.rr.com wrote:
> > > Is madvise required to result in zero filled pages
> > > by a standard, or is this just the commonly accepted
> > > behavior?
> >
> > I believe it is the standard for clean pages, though someone else will have
> > to point out where...
>
> That's the answer to a different question.
>
> The unanswered question is: what should madvise(MADV_DONTNEED) do,
> given dirty pages?
>
> man madvise(*) says that it zero-fills anonymous private mappings, and
> restores private file-backed mappings to the original file pages.
>
> That is not surprising, as the CPU-friendly semantic is more
> complicated to implement, needing an extra flag in the page table
> (or rmap structure).
>

Sounds entirely reasonable.

It *would* be nice with a way to be able to say to the kernel "you may
discard this but if so I want SIGSEGV", for things like LPSM and the
like.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
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