🚀 go-pugleaf

In article <41c9ut$g73@usenet.ucs.indiana.edu>,
scott goehring <sgoehrin@copper.ucs.indiana.edu> wrote:

>>True.  Pre-emptive is more efficient and smoother, which is why it was
>>added into 95.
>
>preemptive multitasking is _less_ efficient than nonpreemptive
>multitasking, because of preemption overhead.  many supercomputers run

The overhead is insignificant. One hundred clock ticks per second
are nothing to a modern CPU. Even the Commodore 64 had a 60hz clock
tick for updating the clock and hooking in user interrupt routines.
You don't know what you are talking about.

The cost of having to place yield calls in "cooperative" code
is greater. The loss of scalability is also pitiful. How do you scale
cooperative threads to a symmetric multi-processor, when they are
designed with the tacit understanding that no concurrent execution
happens as long as you don't yield the CPU?

>however, maximizing CPU utilization is not generally the goal of most
>systems; balancing CPU utilization with user responsiveness is a more
>common goal.

The user responsiveness of a "cooperative" system with a runaway
"background process" is simply astounding.

>preemptive multitasking was developed largely to support "time sharing
>systems".  read up on the history of computing.

>i guess this all goes to prove that "those who do not learn from
>history are doomed to repeat it."  all of this nonsense has been done
>before, just on different computers by different companies.

You are forgetting that the cooperative nonsense was also done before,
and is repeated by fools who do not learn from even earlier history.

Mac programmers didn't learn from the history of the IBM 360
architecture, which--- almost exactly like the 68000---had 32 bit
address registers, but with only 24 external address lines (the 68K has
the least significant line decoded into an data strobes).  Some
programmers used the "extra" bits as pointer tags, making their code
non-portable to full, 32-bit implementations of the architecture.
Twenty years later, some Mac programmers were guilty of doing the same
thing.

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