Re: [RFC][PATCH] O(1) Entitlement Based Scheduler

[Peter Williams]

Nuno Silva wrote:
> Timothy Miller wrote:
>
> [..]
>
> > It's a security concern to have to login as root unnecessarily.  It's 
> > bad enough we have to do that to change X11 configuration, but we 
> > shouldn't have to do that every time we want to start xmms.  And just 
> > suid root is also a security concern.
>
> Maybe I'm missing something, but xmms run OK with zero load, right? The 
> problem is that, when building the kernel and the entire kde tree, each 
> with make -j 16, xmms skips a few times? Well, tough luck...
>
> And the user *can* do something about it, just nice -n 19 the builds and 
> left xmms alone. (Or you can use other player... :-)
>
> With this patch you can even say that each of the build processes can 
> only hog 5% (at the most!) of the CPU (maybe the build is not a good 
> example for mandatory CPU time caps, but it is usefull).
>
> Besides, this implements a true run-only-when-noone-else-wants-to-run 
> nice mode wich, combined with the absolut cpu time caps, hits some of my 
> wish list for a complete scheduler :-) so I can't wait to test it :-)

Another idea that we are playing with for handling programs like xmms 
(i.e. programs that require gauranteed CPU bandwidth to perform well) is 
the complement of caps namely per task CPU reservations.  The 
availability of CPU usage rate statistics for each task makes this 
possible but the question is "Is the functionality worth the extra 
overhead?".

Of course, this won't solve the "need to be root" problem as this is 
obviously the sort of control that should be reserved for root but it is 
arguably better than having to guess how many shares a task needs to 
ensure that it gets the required CPU bandwidth.

Peter
--
Dr Peter Williams, Chief Scientist                peterw@xxxxxxxxxx
Aurema Pty Limited                                Tel:+61 2 9698 2322
PO Box 305, Strawberry Hills NSW 2012, Australia  Fax:+61 2 9699 9174
79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com


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