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SubjectRe: [PATCH] sched/deadline: Add sched_dl documentation
On 01/27/2014 01:40 PM, Henrik Austad wrote:
[...]
>>> Current runtime: time spent running _this_ period? or is _remaining_
>>> runtime this period? I get the feeling it's the latter.
>>>
>>> So, roughly, it is the ration
>>>
>>> remaining_runtime / relative_time_to_deadline
>>>
>>> which needs to be greater than the assigned CPU bandwidth, and if so, the
>>> budget should be replensihed?
>>>
>>> Shouldn't there be something about not refilling the budget before a new
>>> period has started?
>> Uh... Maybe the description above can be improved :)
>> Do you think that using "remaining runtime" instead of "current runtime"
>> would help? If yes, I'll make this change.
>
> Yes, in my vocabularly, "remaining" != "current" :), so changing to
> 'remaining runtime' would be nice.
Ok; I'll make this change.


>> Also, I see that some of your questions are answered by some items below...
>
> Yes, but I left the comments to indicate that the order was a bit
> confusing.
>
>> Do you think that changing the order of the items in the presentation would
>> improve the readability? If you suggest a better ordering, I'll try to
>> rewrite the algorithm's description according to it.
>
> Could be, at least the ratio-caclulation was a bit confusing until I'd read
> the entire section.
>
> My preferred order (I've just cut'n'pased from the original email here)
>
> + - The state of the task is described by a "scheduling deadline", and
> + a "current runtime". These two parameters are initially set to 0;
BTW, maybe some of the confusion can be avoided by explaining what the
"remaining runtime" is here... Something like:
- The state of the task is described by a "scheduling deadline", and
a "current runtime" (representing the amount of execution time that
the task can use before the scheduling deadline). These two parameters
are initially set to 0;

Can something like this help? If yes, I'll update the document.


[...]
> + - When a SCHED_DEADLINE task wakes up (becomes ready for execution),
> + the scheduler checks if
> +
> + current runtime runtime
> + ---------------------------------- > ----------------
> + scheduling deadline - current time period
> +
> + then, if the scheduling deadline is smaller than the current time, or
> + this condition is verified, the scheduling deadline and the
> + current budget are re-initialised as
> +
> + scheduling deadline = current time + deadline
> + current runtime = runtime
> +
> + otherwise, the scheduling deadline and the current runtime are
> + left unchanged;
> +
>
> Emphasis on -my- preferred order. :)
Ok; let's see what other people think, and then we decide the items'
order.


> Either way, I'm quite happy with this documentation-update, this is just
> nitpick :)
Ok, good.


Thanks,
Luca



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