Re: Interesting VM feature?

[H. Peter Anvin]

Followup to:  <20030815211937.GA20208@xxxxxxxxxxxxxxxxxx>
By author:    Jamie Lokier <jamie@xxxxxxxxxxxxx>
In newsgroup: linux.dev.kernel
>
> Mike Fedyk wrote:
> > On Fri, Aug 15, 2003 at 02:56:02PM -0500, mouschi@xxxxxxxxx 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
-- 
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