[LITMUS^RT] prop/edf-early-release

[Jonathan Herman]

Distinguishing between sporadic, periodic, and early release tasks has also
been an issue in my plugins. I have usually been forced to assume periodic,
but inevitably someone wants to see early release results in the graphs.
Thumbs up.

The task wake_up code in a few of the plugins assumes a sporadic model.
This code would also have to be changed for full periodic support.


On Tue, Mar 5, 2013 at 8:41 PM, Glenn Elliott <gelliott at cs.unc.edu> wrote:

> Hi All,
>
> I've run into a number of applications where early job releasing would be
> useful.  Specifically, this is in the context of interrupt handling
> threads, non-root PGM graph nodes, and bandwidth servers.  Tasks must be
> explicitly configured for early releasing: prop/edf-early-release adds a
> new field to the task params.  Note that early releasing is only supported
> by EDF.
>
> The patch is simple and unobtrusive, but I understand if this isn't
> desired for mainline.  I've posted the patch to github.
>
> From the commit:
>
> commit 60d107ca171413cc5f765e51aa0c4cd6848e139e
> Author: Glenn Elliott <gelliott at cs.unc.edu>
> Date:   Tue Mar 5 20:03:04 2013 -0500
>
>     EDF schedulers: Support early job releasing.
>
>     This patch allows a task to request early releasing
>     via rt_task parameters to sys_set_task_rt_param().
>     Note that early releasing can easily peg your CPUs
>     since early-releasing tasks never suspend to wait for
>     their next job. As such, early releasing is really
>     only useful in the context of implementing bandwidth
>     servers, interrupt handling threads (or any thread that
>     spends most of its time waiting for an event), or
>     short-lived computations. If early releasing pegs your
>     CPUs, then you probably shouldn't be using it.
>
> -Glenn
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-- 
Jonathan Herman
Department of Computer Science at UNC Chapel Hill
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