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Re: DSR Scheduling Problem


Nick Garnett <nickg@ecoscentric.com> writes:
[...]
> Stefan's patch, give or take a bit of tidying and name changing, looks
> just fine.

Please consider documentation worries I have in the reply to Grant's
objections I'm going to post in a few minutes.

> Adding and removing DSRs remains deterministic, if not quite
> constant-time, and resolves any reservations I might have about adding
> FIFO queueing.

What's less constant-time in FIFO w.r.t. LIFO? Did I miss something?

> Most systems do not have interrupts occuring at the sort of rate that
> would make DSR queueing order make any difference.

I'm confused. Did you miss in my analysis that maximum DSR latency
doesn't depend on the rate of interrupts? It was in fact one of my
primary assumptions that interrupts are rare. I.e., FIFO wins at low
interrupt rates.

> So we should default to the very simplest approach and document the
> tradeoffs of each mechanism. Subsytems and drivers that really want
> FIFO queueing can always have a "requires" statement in their CDL for
> this option.

If the above indeed were the case, I'd have no objections, but I still
fail to see *real* trade-offs of FIFO w.r.t. to LIFO.

-- Sergei.


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