Re: Applications "buying" resources



On 12/30/2010 2:40 AM, upsidedown@xxxxxxxxxxxxx wrote:
On Thu, 30 Dec 2010 01:43:56 -0700, D Yuniskis
<not.going.to.be@xxxxxxxx> wrote:

My RTOS has hooks that let the "kernel" ask tasks
(forget how that is defined) to voluntarily shed
resources (time, memory, power). This lets the
kernel (actually, a "special" user-land task that
makes decisions *for* the kernel) throttle back
the demands placed on the *fixed* resources to
better adjust to the current demands placed on them.

So, if some "new" task needs to be spawned and
needs some resources, the kernel can ask the
currently running set of tasks to relinquish
resources that they may be holding but not *needing*.

During the last few decades, I have written a few successful control
systems using simple fixed priority real time operating systems
without problems.

The key issue is that any high priority task should use as little
resources as possible. The lowest priority task can use as much
resources it likes.

This approach only works in a static system. If the number of
consumers changes, then the strategy falls apart.

Note that (process) control systems tend to be VERY static:
"do this... FOREVER".

Could your systems work if some arbitrary third party was
allowed to add his code to your code base (assuming he wasn't
allowed to "touch" your code) and WITHOUT changing any of the
hardware?
.