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Re: [Xen-devel] [RFC Patch 0/3] Putting the "Simple" back in sedf.

On 3/14/2014 4:13 PM, Nate Studer wrote:
> On 3/14/2014 3:22 PM, George Dunlap wrote:
>> On 03/14/2014 07:13 PM, Nathan Studer wrote:
>>> From: Nathan Studer <nate.studer@xxxxxxxxxxxxxxx>
>>> With the increased interest in embedded Xen, there is a need for a suitable
>>> real-time scheduler.  The arinc653 scheduler currently only supports a
>>> single core and has limited niche appeal, while the sedf scheduler is
>>> widely consider deprecated and is currently a mess.
>>> Since both the CBS scheduler proposed by Dario and the schedulers of Xen-RT
>>> use an edf scheduler as the lowest-level scheduling mechanism, it seems
>>> worthwhile to start repurposing the sedf scheduler instead of creating a
>>> completely new scheduler.
>>> This patchset begins this repurposing by removing the extra scheduling code
>>> that has built up over the years, and returns the sedf scheduler to its
>>> simple roots.
>> Hey Nate,
>> Thanks for these patches -- what you describe at a high level, making 
>> sedf a suitable rts for embedded applications, sounds like a great idea.
>> I think what might be helpful in evaluating whether these patches are a 
>> good idea at the high level is a bit of a description of where you see 
>> this going long-term.  Can you sketch out, at a high level, what you 
>> envision the sedf scheduler becoming?  What kinds of parameters and 
>> features *will* it have?
> In the long term, a more extensible version of Dario's favorite scheduler, CBS
> (Constant Bandwidth Server):  a selectable budgeting algorithm that sets vcpu
> deadlines with the sedf scheduler on the backend scheduling the vcpu with the
> earliest deadline.  Preferably it would support other budgeting algorithms as
> well such as Total Bandwidth Server, etc...

Speaking of Dario, I got his e-mail address wrong. My apologies.

CC'ing his correct address.

> The parameters for the scheduler would be the budgeting algorithm, server
> budget, and the server period.  The parameters for the domains/vcpus would be
> domain/vcpu budget/timeslice and domain/vcpu period.
> Those are our ideas though and I know that Dario and others have ideas as 
> well,
> so any feedback is appreciated.
> In the short term, we are working on upstreaming a version of the CBS 
> scheduler.
>  Dario mentored Josh Whitehead, who works with me, in implementing a crude
> version of it for his undergraduate project, so we are already half-way there.
> http://wiki.xen.org/wiki/Archived/GSoC_2013#Temporal_Isolation_and_Multiprocessor_Support_in_the_SEDF_Scheduler
>    Nate
>>   -George
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