regarding r242905 ('us' argument to some callout functions) was Re: [RFC/RFT] calloutng
Alexander Motin
mav at FreeBSD.org
Mon Dec 17 19:59:46 UTC 2012
Hi.
> I wonder why the choice is to use (actually, call) the value
> "microseconds" rather use a bintime or something scaled and with a
> well defined resolution.
It was kind of engineering choice. I've chosen microseconds, following
values used by ACPI to represent CPU sleep states exit latencies. Now
that is the only usage for that value. If CPUs so much reduce wakeup
latencies to make this scale too coarse, this type will be the smallest
of our optimization tasks. On the other side, I have some doubts that we
will be able to reach supported 2048 seconds limit on the integer side.
Now even completely empty idle system has about 30 interrupts per
second, that is far from 0.0005. From the other side, I don't know any
system where CPUs have 2048 seconds wakeup latency.
--
Alexander Motin
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