Re: [ckrm-tech] Re: [RFC] Revised CKRM release

[Shailabh Nagar <nagar@watson.ibm.com>]

Rik van Riel wrote:
> On Fri, 30 Apr 2004, Christoph Hellwig wrote:
> 
> 
>>I'd hate to see this in the kernel unless there's a very strong need
>>for it and no way to solve it at a nicer layer of abstraction, e.g.
>>userland virtual machines ala uml/umlinux.
> 
> 
> User Mode Linux could definitely be an option for implementing
> resource management, provided that the overhead can be kept
> low enough.

....and provided the groups of processes that are sought to be 
regulated as a unit are relatively static.


> For these purposes, "low enough" could be as much as 30%
> overhead, since that would still allow people to grow the
> utilisation of their server from a typical 10-20% to as
> much as 40-50%.
> 

In overhead, I presume you're including the overhead of running as 
many uml instances as expected number of classes. Not just the 
slowdown of applications because they're running under a uml instance 
(instead of running native) ?

I think UML is justified more from a fault-containment point of view 
(where overheads are a lower priority) than from a performance 
isolation viewpoint.

In any case, a 30% overhead would send a large batch of higher-end 
server admins running to get a stick to beat you with :-)