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Re: CVS commit: src/sys/net
On Wed, Feb 17, 2016 at 4:52 PM, Taylor R Campbell
> Date: Wed, 17 Feb 2016 15:12:31 +0900
> From: Ryota Ozaki <ozaki-r%netbsd.org@localhost>
> On Wed, Feb 17, 2016 at 2:13 PM, Taylor R Campbell
> <campbell+netbsd-source-changes-d%mumble.net@localhost> wrote:
> > Note that this queueing takes effect only if the link state changes
> > multiple times within maybe a few microseconds, before the softint can
> > run. If your link state is changing that many times so quickly,
> > losing an event or two is probably the least of your worries
> Yeah, it's nitpicking, but for that reason, I think it's better to pass
> events as they are to userland.
> > -- but
> > you're probably more interested in seeing something like ...down...up
> > than ...up/up/up.
> Yes. (up/up/up events are eliminated in the first place though.)
> So what events would you choose to skip, if not the scheme that Roy
(I think I confused you, sorry...)
I rather want to not skip anything as much as possible
(except for repeating same events (e.g., up/up/up) because
keeping them all changes the original behavior).
I intend to skip/eliminate events only if there are too many
events happen in a short period (i.e., need queuing) to protect
the system from overloading. In that case (it's a very rare case
I think), we just drop an earliest event first.
> I bet that, whatever events you would choose to skip, we can still
> prove that the resulting queues need be no longer than, say, three
> elements, and we'd still usefully report link flapping to userland --
> as long as we can make enough progress to run softints and userland
> processes at all.
> Here are some example reductions that intuitively sound reasonable to
> down/down = down
> up/up = up
> down/unknown/up = down/up
> down/up/down = down
> What other sequences of events would you simplify?
As I said, I want to keep the sequences (except for repeating same events)
so the last two examples will be sent as they are.
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