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why programs behave nicely and protecting against those that don't


From: Neal H. Walfield
Subject: why programs behave nicely and protecting against those that don't
Date: Thu, 26 Jun 2008 16:17:47 +0200
User-agent: Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shij┼Ź) APEL/10.6 Emacs/21.4 (i486-pc-linux-gnu) MULE/5.0 (SAKAKI)

At Thu, 26 Jun 2008 13:32:53 +0200,
Bas Wijnen wrote:
> > When we report the availability to the child, we will not report 35,
> > but perhaps 34 so as to encourage it to free a bit more memory.
> 
> A well behaving child would gladly do this, while a badly behaving child
> wouldn't do it anyway, right?  Why then not just give real numbers (35)
> and let the child be nice explicitly?

A major premise is that most programs are well-intentioned.  Of the
rest, some are misbehaving and a few are actively malicious.  This
does not mean that we can ignore those programs.  Far from it.  In
your scenario, if a program does not adapt, the OS will page it.  The
motivation behind adapting is that adapting is less expensive than
being paged.  Thus, the incentive is to adapt where possible.

For those programs that are really interfering, a user can always
reduce its share or destroy the activity it is using to allocate
resources.  Destroying an activity is mostly equivalent to shooting a
space bank on EROS.  That is, it doesn't ask the program to quit, it
simply destroys its storage.




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