[EMAIL PROTECTED] wrote:
>
> On Tue, Sep 05, 2000 at 10:18:25AM -0700, David Schleef wrote:
> > I don't think that "running out of memory" and "running out of CPU
> > time" are fundamentally different things. It's just that with a
> > memory allocator, you are notified of a lack of resources and can
> > do something graceful instead of locking the machine.
>
> Sure. But I think there is a significant difference between:
> 1. At startup time, allocate N buffers for a pool
> for a particular purpose and have an allocate/free
> routine.
> and
> 2. Maintain a general purpose buffer pool with unknown
> size and many users.
>
>
Hi Victor,
I think the big misunderstanding is that the pool of memory is only
available to real-time tasks. This means that a design can be made
based upon things you can control, whereas in a soft real-time system,
you are subject to the interference of things you cannot control (such
as a disk surge from an active web server for instance). In the same
way you have to take care not to exceed the maximum frame time allocated
per task (CPU budget), you must also take care that you understand the
limitations of the memory allocator (e.g don't ask for too much too
quickly).
Remember also that people seem to be thinking here in terms of a task
meeting its deadline with high precision every time. That is fine for
the highest priority task, but if you have many task, the lower priority
tasks will have significant jitter. Again, only a problem if you don't
take this into account in the design.
Regards, Stuart
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