Re: Scheduling

[Stephan Diestelhorst <sd386@cl.cam.ac.uk>]

>I am now changing my scheduling and have noticed some different results,

>perhaps you could help me in my studies....
>
>I am running CPU intensive VMs and am trying to find out at what
>scheduling they'll run the best (since the simulation being run over a
>long duration, short periods and slices are not important).  I have 8
>VMs so my first few tests were running in periods of 1, 2, and 10
>seconds, divided among the 8 domUs... 
>  
>
>So I typed
>Xm sedf (1,8) 1,2,10e9 125,250,1250e6 0 0 0
>(ie, xm sedf 1 1000000000 125000000 0 0 0)
>
>In this case, I excluded scheduling for dom0...
>
>Could you please help me refine my scheduling.
>
>  
>
Sure. Actually I have not thought of such long periods and slices and in
fact there are parts in the code that limit the slice and period lengths
to roughly 4 seconds (due to arithmetic overflow), as I guessed that
those long periods would be quite exotic. In fact I think you might be
better of to use the scheduler in extra-time mode, that means you don't
guarantee time to the domains, but rather split the remaining (i.e. when
all realtime domains have finished) time into pieces of various sizes.
I guess this might be more appropriate to you, I assume that your long
running simulation is not a real-time application?

So you might just try to do
xm sedf (1,8) 0 0 0 1 w
With w specifying a weight for the domain. This works intuitively, so a
domain with weight 4 gets twice the amount of CPU time as one with
weight 2, which gets 2/5 of one with weight 5.

I hope that this suits your needs, if not, let me know and I'll change
some of the arithmetic code.
BTW: What did actually happen when you used the above command?

Stephan

>-----Original Message-----
>From: Ian Pratt [mailto:m+Ian.Pratt@cl.cam.ac.uk] 
>Sent: Monday, July 25, 2005 11:50 AM
>To: Wolinsky, David; xen-devel@lists.xensource.com
>Cc: ian.pratt@cl.cam.ac.uk
>Subject: RE: [Xen-devel] Scheduling
>
> 
>  
>
>>Added sched=rrobin to my kernel and started xen Ran xm rrobin, unknown
>>    
>>
>
>  
>
>>command Ran xm help rrobin, unkown command
>>    
>>
>
>sched=rrobin is not in unstable anymore. 
>
>The default is the SEDF scheduler, but you can still set sched=bvt
>
>As I recall, there is some documentation on SEDF in tools/misc
>
>We should file a bug that using a scheduler op on a non existent
>scheduler does bad things.
> 
>Ian
>
>  
>
>>So round robin is throw out
>>
>>So I tried the default bvt...
>>Without appending it to my kernel, I ran... xm bvt_ctxallow 1 -
>>Error:  Internal server error
>>
>>With it appended to my kernel, I run.. 
>>xm bvt_ctxallow 1 - Computer hard crashes
>>
>>Any suggestions? 
>>
>>Thanks,
>>David
>>
>>
>>    
>>
>
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