sedf internals question

sedf internals question

[Tim Freeman]

With SEDF, let us say a domain has a certain timeslice allocated to it (say, 500
units) for a certain period (say 1000).  It runs for 200, then blocks.  When it
has become unblocked, the domain is put on the runqueue -- but say we are at the
end of the period, maybe 900 units in.  Even if it immediately runs for 100
units, what happens to the extra 200 units it is guaranteed? 

Thanks,
Tim 

Re: sedf internals question

[Stephan Diestelhorst]

Hi Tim,

>With SEDF, let us say a domain has a certain timeslice allocated to it (say, 500 units) for a certain period (say 1000).  It runs for 200, then blocks.  When it has become unblocked, the domain is put on the runqueue -- but say we are at the end of the period, maybe 900 units in.  Even if it immediately runs for 100 units, what happens to the extra 200 units it is guaranteed? 
>  
>
Those guaranteed 500 units get binned once a domain blocks, because, as 
you already pointed out, the scheduler can't make anymore guarantees at 
that point. It can however give some of the suddenly available idle-time 
to the domain. This is done by a priority scheme that supports those 
domains most, that lost most of their time due to blocking. There are 
(or used to be?) some different approaches in sched_sedf.c, which are 
selectable at compile-time by exchanging macros. Play with those if you 
want to tweak your system, although my measurements suggested the one 
that is curently used to be the most useful. (And please send me some of 
your results if you do ;-) )

Cheers,
  Stephan

Re: sedf internals question

[Gaurav Somani]

Dear Stephen,

I want to know the importance of the extra command line field in sedf
scheduler. which is l (latency). It only says about when  domain does high
I/O work. What does it mean by "high"?
please give me the way. It will elp me in my research.

Thanks 
Gaurav
onlineengineerATgmailDOTcom



Stephan Diestelhorst-2 wrote:
> 
> Hi Tim,
> 
>>With SEDF, let us say a domain has a certain timeslice allocated to it
(say, 500 units) for a certain period (say 1000).  It runs for 200, then
blocks.  When it has become unblocked, the domain is put on the runqueue --
but say we are at the end of the period, maybe 900 units in.  Even if it
immediately runs for 100 units, what happens to the extra 200 units it is
guaranteed? 
>>  
>>
> Those guaranteed 500 units get binned once a domain blocks, because, as 
> you already pointed out, the scheduler can't make anymore guarantees at 
> that point. It can however give some of the suddenly available idle-time 
> to the domain. This is done by a priority scheme that supports those 
> domains most, that lost most of their time due to blocking. There are 
> (or used to be?) some different approaches in sched_sedf.c, which are 
> selectable at compile-time by exchanging macros. Play with those if you 
> want to tweak your system, although my measurements suggested the one 
> that is curently used to be the most useful. (And please send me some of 
> your results if you do ;-) )
> 
> Cheers,
>   Stephan
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 
> 

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