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Re: Broken dream of mine :(

From: Michal Suchanek
Subject: Re: Broken dream of mine :(
Date: Wed, 4 Nov 2009 15:02:33 +0100

2009/11/4 Sam Mason <address@hidden>:
> On Wed, Nov 04, 2009 at 12:39:05PM +0100, Michal Suchanek wrote:
>> This is not something that is completely addressed in Coyotos either -
>> there still can be observable increase in latency when the system is
>> under load. Coyotos aims to get nearer to the absolute isolation
>> ideal, though.
> AFAICT, it is possible to arrange things in Coyotos so that (say) things
> don't get swapped to disk and that memory is always available for the
> services that need it.  There were various discussions about this to do
> with windowing systems; for example, you want to know that you'll always
> be able to bring up a "task manager" to kill off offending processes,
> hence a way of reserving the appropriate resources for this in advance
> is needed.  This example involves quite complicated interactions between
> lots of different services needed to do its work and arranging all this
> is somewhat difficult.

You have completely missed the point. Even in Coyotos if you did not
pin your pages in memory so that they never get "swapped out" (and
most applications should not be able to pin) then your pages are much
more likely to get "swapped out" when other applications run (and
touch their pages)  than when the system is idle. While the "swap in"
may be transparent the latency is observable so you generally get the
same kind of information you get in Viengoos by observing the amount
of surplus memory available to you.

The ability to terminate processes is completely unrelated to this and
in any system that does reasonable resource management it is trivial
to implement. Most systems in use today do not guarantee the ability
to terminate rogue processes but that is a completely different issue.



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