Re: Programming prioritisation

["Barry Cook (4Links)" <barry@xxxxxxxxxxxx>]

Guilty! I said that some good few years ago - although as is the way with such things I expect others have said it as well.

I'll make a similar remark with regard to PRI PAR ...

It seems to me that we're discussing the wrong thing - PRI PAR is an instruction as to how something is to be implemented and is not the real issue.

I suggest that we should be asking how we capture requirement constraints of the form: "when 'this' happens, do 'that' within some time".

Given these constraints we should be able to build a tool to find a solution (or check that our proposed solution will work) ... if we want a hundred counters to respond in 1ns we'll probably need logic gates, a bit slower and lots of processors will do it, slower still and a single processor is OK. An implementation could allow sharing of hardware and if some things need quicker attention than others we may use priority/pre-emption/etc. to meet the constraints in a cost/power efficient way.

    Barry.

Dr Barry M Cook

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On 2012-10-04 17:51, Ruth Ivimey-Cook wrote:

Eric Verhulst (OLS) wrote:

In OpenComRTOS the equivalent of PRI PAR and PRI ALT come together. In my view, they can't be decoupled.

 

1. Tasks get a priority (at compile time). System wide attribute, so independently on which node they have been mapped. On each node, scheduling is in order of priority and preemptive.

This made me think: a long time ago, far far away... .no well anyway a long time ago someone suggested that the real thing that should have a priority attached to it was the communication itself: a message. Not the channel, or the task. The issue in ming, IIRC, was priority inversion. It has always struck me that this was a good model to go with, though I don't recall ever seeing it done or even investigated.

Regards
Ruth

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