Re: [Minios-devel] [UNIKRAFT PATCH v2 4/8] lib/uksched: Introduce thread info

[Florian Schmidt <Florian.Schmidt@xxxxxxxxx>]

On 1/23/19 11:55 PM, Costin Lupu wrote:
> > I have to admit I'm still a bit confused by this explanation. The
> > example you give is about a preemptive scheduler's priority. Why would
> > it duplicate information that is already on the thread? Or is the idea
> There is nothing duplicated. uk_thread_attr is an interfacing structure
> between the user/client/etc and the scheduler.
>
> > that thread priorities might be of a different kind than the scheduler's
> > priorities? But in that case, how would you set them properly,
> Yeah, the scheduler can interpret those values any way it make like.
>
> > considering that pthread is the interface? If the scheduler had more
> > classes than pthread allows, you could not properly use some of them; if
> > it had less, it would have to merge some pthread classes anyway. Or what
> > am I missing?
> I don't follow what you mean by "If the scheduler had more classes than
> pthread allows".
What I mean is that if you do prioritized scheduling, you need to have 
some notion of priority classes, right? That form an order from highest 
priority to lowest priority. Maybe just call them priorities instead of 
priority classes.
The user (=the one who creates the threads) will interface with the 
scheduler via the pthread attributes, I assume? In which case there are 
three possibilities: the scheduler has fewer priority classes than the 
pthread implementation, in which case it needs to map several pthread 
priorities to one scheduling priority; or the scheduler has more classes 
than the pthread implementation, then some classes will not be used 
because there's no way to assign threads to them; or both scheduler and 
pthread have the same number of priorities, then the duplication seems 
useless.
Florian

--
Dr. Florian Schmidt
フローリアン・シュミット
Research Scientist,
Systems and Machine Learning Group
NEC Laboratories Europe
Kurfürsten-Anlage 36, D-69115 Heidelberg
Tel.     +49 (0)6221 4342-265
Fax:     +49 (0)6221 4342-155
e-mail:  florian.schmidt@xxxxxxxxx
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