Hubertus,

A PlanetLab node typically has about a dozen or so active vservers (aka
slices), but there are typically ~150 vservers put onto a such a node.

This means that I will have to likely create 150 or so entries in the
/rcfs/taskclass directory. Presumably your scheduler only considers "active
classes" i.e., those which have running processes, rather than all classes,
right?!

Any way, those are the round numbers for the typical use on PlanetLab which
CKRM's cpu must support.

Marc

-----Original Message-----
From: Hubertus Franke [mailto:[EMAIL PROTECTED]
Sent: Wednesday, September 22, 2004 11:57 AM
To: Shailabh Nagar
Cc: Marc E. Fiuczynski; ckrm-tech
Subject: Re: [ckrm-tech] I/O controller for e16



>
> Even if one can declare 100's of CPU classes, isn't there a limitation
> on _effectively_ how many distinct levels of CPU share can be supported
> ? Whats the highest that has been tried ?
>
>

We tried 5-10 .. But that doesn't matter.

First the share settings truely accept the share/total_share
calculation. So if you are willing to go up to a larger level of
total_share then CPU scheduler can distinguish that ..

The main reason can be seen from include/linux/ckrm_sched.h   in
update_local_cvt.

Here we adjust the normalized (by the effective share of the class)
the nanosecs a task ran at deschedule time.

nsecs are typically large while weights are < total_share.

So given the above I think we can distinguish CPU shares in the order
of 100 classes.

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