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Re: Broken dream of mine :(

From: olafBuddenhagen
Subject: Re: Broken dream of mine :(
Date: Fri, 6 Nov 2009 23:36:44 +0100
User-agent: Mutt/1.5.19 (2009-01-05)


On Wed, Nov 04, 2009 at 12:39:05PM +0100, Michal Suchanek wrote:

> The main difference as I understand it is that Coyotos enforces 'hard'
> resource allocation - the resource either is allocated to the process
> or it is not.
> In Viengoos surplus resources that are not in use by any process can
> be used by processes that are interested.

This misses the point IMHO. It's not really about "used" and "surplus"
resources. (Aside from pinned pages, no strict notion of "used" RAM
exists in any system implementing virtual memory.)

The real point of the Viengoos approach is allowing applications to take
part in resource distribution decisions, instead of the system trying to
guess requirements.

> This leads to better utilization of resources but somewhat loosens
> security. Processes can see how the system is starved for resources
> and artificially modulate resource demand to create a communication
> channel.


> 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.

Indeed -- and I'm not at all convinced that "getting nearer" is really a
worthwhile goal in practice.


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