Re: Java or C++?


Scott Moore wrote:
> jimmaureenrogers@xxxxxxxxxxxxxxxx wrote On 10/28/05 13:01,:
> > Scott Moore wrote:
> >
> >>There are gcol algorithims that don't impact real time performce. The collection
> >>process can be run only when the processor is completely idle, and constructed
> >>in such a way that it is both interruptable and preemptable.
> >

>
> Sorry, but I have worked for many people who held these theories about
> their code, and the code didn't bear it out. What in fact was happening was
> that they were mixing various amounts of polling and other time wasting
> activities into the system, then calling the system "busy". There are
> many ways to fool yourself that you aren't polling when you are.
> A typical scenario is where the interrupt handler sets some flags, then
> the tasks running wake up, check those flags, then give up their timeslice
> when the flags don't prescribe action needed. That's not a non-polling
> algothim, that's moving the status of a pheripheral to a flag, then
> polling that in round robin fashion.
>
> The idea of a "fully busy" processor for real time is against the
> entire concept of real time in any case. If the machine is fully
> occupied, then it is on the edge of failing, because if its load increases
> even a little, it then fails. The theory of real time computing is that
> the CPU is run far below its load level to keep the latency to handle
> real time events low. Given this, yes, you always have idle time on
> the CPU, and that time can be used as I mentioned.
>
> I have worked on several projects which had an "overloaded CPU" and
> the problem was solved by eliminating polling and other wasted work,
> which resulted in dramatic decreases in CPU workload.

I agree with what you just said, but that is different from what
I first responded to. You specified that the garbage collector could
run when the processor was completely idle (see the quotation above).
This is far different than when the processor is not fully occupied.

Jim Rogers

.

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