[cgl_discussion] requirements for configurable Round Robin quantum and 1 ms tick

Peter Badovinatz tabmowzo at us.ibm.com
Tue Aug 12 10:13:14 PDT 2003

Eric.Chacron at alcatel.fr wrote:


I've been traveling quite a bit during and since Ottawa, am traveling
again.  So, I actually missed this (it was buried in my in-box). 
Apologies on that.

> Today some applications need to use Real Time process with Round Robin
> policy.
> Today the quantum seems to be defined by a constant value as 20 x the tick
> value.
> Then if i use a 10ms tick the quantum is equal to 200 ms. This seems too
> large.
> A second requirement could be to enable a 1 ms tick period for the timer
> interrupt on Intel Pentium architectures.
> Is'it compatible with kernel maximum latency ? ( remenber that some
> application runs whithout any disk and without
> related sources of latency like fork+ exec ...)
> I would like to have the feed-back from everyone who's interrested in the
> question and also from Montavista
> as ther could be some link with low latency and RT scheduler for the second
> point.

According to the "rules" from Ottawa, we aren't intending to add any
additional requirements.  Very specifically, no priority ones.  That
said, we do have an open "soft real time" (PRF.1.0) v2.0 requirement
which rolls together the latency and premption requirements.

What I'm wondering about is if your requests could be included with
PRF.1.0?  The question is if these are already possible and potentially
supported, I have no problem adding them.  If these require additional
work and don't easily fit into the current work, we may be out of luck
for v2.0.

I'll echo your comment, we need folks with more knowledge of scheduling
and real time to step in.

Peter R. Badovinatz aka 'Wombat' -- IBM Linux Technology Center
preferred: tabmowzo at us.ibm.com / alternate: wombat at us.ibm.com
These are my opinions and absolutely not official opinions of IBM, Corp.

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