Re: [Xen-devel] xen 4.5.0 rtds scheduler perform poorly with 2vms

[Meng Xu <xumengpanda@xxxxxxxxx>]

2015-11-29 11:18 GMT-05:00 Dario Faggioli <dario.faggioli@xxxxxxxxxx>:
>
> On Sun, 2015-11-29 at 04:46 -0800, Yu-An(Victor) Chen wrote:
> > So st_jobs_stats for the missed deadline jobs are:
> >
> > trial #1 composed of 2 tasks: total tasks utilization rate = 1
> >
> > (period, exe, deadline)=(21ms,12.023ms,21ms) -> miss all deadline
> > (period, exe, deadline)=(100ms,37.985ms,100ms) -> no miss
> >
> > trial #2 composed of 2 tasks: total tasks utilization rate = 1
> >
> > (period, exe, deadline)=(68ms,40.685ms,68ms) -> miss all deadline
> > (period, exe, deadline)=(70ms,28.118ms,70ms) -> no miss
> >
> > trial #3 composed of 2 tasks: total tasks utilization rate = 1
> >
> > (period, exe, deadline)=(16ms,11.613ms,16ms) -> miss all deadline
> > (period, exe, deadline)=(46ms,12.612ms,46ms) -> no miss
> >
> The point is: how did you come up with these numbers? What both me and
> Meng are trying to say is that the budget(s) and period(s) of the
> (vCPU's of a) VM and the budgets and periods of the task running inside
> the VM must fulfill certain relationships, or schedulability is not
> something you can even hope for! :-/
>
> > I do notice that for within the task that misses deadline, the
> > completion time get progressively longer,
> > for example: for trial #3, a snapshot of the task st_jobs_stats tells
> > me that
> > the completion time of the job is 79ms and then 87ms, and then 95ms
> >
> That depends on how missing a deadline is handled and accounted for. I
> don't recall how Litmus^RT does that.


LITMUS by default let the task keep running even when it misses deadline.
But if users specify the enforce_budget (the name may be a little
different), it will abandon the unfinished work at deadline miss.

Meng



-- 


-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
http://www.cis.upenn.edu/~mengxu/

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel