RE: gradual timeofday overhaul

[Perez-Gonzalez, Inaky]

> From: George Anzinger [mailto:george@xxxxxxxxxx]
>
> > This is just talking out of my ass, but I guess that for each invocation
> > they will have more or less the same overhead in execution time, let's
> > say T. For the periodic tick, the total overhead (in a second) is T*HZ;
> > with tickless, it'd be T*number_of_context_switches_per_second, right?
> 
> ???  Better look again.  Context switches can and do happen as often as 10 or so
> micro seconds (depends a lot on the cpu speed).  I admit this is with code that
> is just trying to measure the context switch time, but, often the system will
> change it mind just that fast.

As I said, I was talking out of my ass [aka, I didn't know and was just 
guesstimating for the heck of it], so I am happily proven wrong--thanks to
Chris and you--I guess I didn't take into account voluntary yielding of
the CPU by a task; I was more guiding myself for kicked out by a timer
making a task runnable, or a timeslice expiring, etc...which now are 
more or less guided by the tick [and then of course, we have IRQs,
but that's another matter]

> ...
> sourceforge).  On the other hand, where I come from, a system which has
> increasing overhead with load is one that is going to overload.  We are always
> better off if we can figure a way to have fixed overhead.
> 
> As for the idle system ticks, I think the VST stuff we are working on is the
> right answer.

Once my logic is proven wrong, then it makes full sense :]

Thanks for the heads up.

Iñaky Pérez-González -- Not speaking for Intel -- all opinions are my own (and my fault)
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