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Re: EROS/Coyotos fault handers vs l4 pager hierarchy


From: Marcus Brinkmann
Subject: Re: EROS/Coyotos fault handers vs l4 pager hierarchy
Date: Sun, 23 Oct 2005 20:33:26 +0200
User-agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.7 (Sanjō) APEL/10.6 Emacs/21.4 (i386-pc-linux-gnu) MULE/5.0 (SAKAKI)

At Sun, 23 Oct 2005 13:25:33 -0400,
"Jonathan S. Shapiro" <address@hidden> wrote:
> 
> On Sat, 2005-10-22 at 12:39 +0200, Marcus Brinkmann wrote:
> > That's not a bad counter-example.  Except that in the Hurd/L4 design,
> > swapping is voluntary and explicit.
> 
> What happens when you run out of physical pages and you want to start a
> new process? Given that the vast majority of processes are untrusted,
> how to you guarantee that they give up storage?

Well, those are good questions, and we didn't find a satisfactory
answer yet.

Neal's idea was that the guaranteed physical memory contingent that a
process (or user) receives is negotiated in a long-term contract,
which periodically must be renegotiated.  At renegotiation time, the
process gets a chance to swap pages out to disk.  After this chance
passed, pages may be revoked forcefully.

Renegotiation of resources could for example handled with a
market-model.

Note that these were only very rough ideas.  Neal has worked them out
in some more detail than I present them here, but we are aware (of at
least some) of the problems with these suggestions.

Thanks,
Marcus






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