[RFC/RFT] calloutng

[Kevin Oberman]

On Wed, Jan 2, 2013 at 2:06 PM, Alexander Motin <mav at freebsd.org> wrote:
> On 02.01.2013 18:08, Adrian Chadd wrote:
>>
>> .. I'm pretty damned sure we're going to need to enforce a "never
>> earlier than X" latency.
>
>
> Do you mean here that we should never wake up before specified time (just as
> specified by the most of existing APIs), or that we should not allow sleep
> shorter then some value to avoid DoS? At least on x86 nanosleep(0) doesn't
> allow to block the system. Also there is already present mechanism for
> specifying minimum timer programming interval in eventtimers(9) KPI.

I can see serious performance issues with some hardware (wireless
comes to mind) if things happen too quickly. Intuition is that it
could also play hob with VMs.

I believe that the proper way is to wake between  T_X and T_X + D.
This assumes that D is max_wake_delay, not deviation, which leaves us
at the original of (T_X) =< event_time =< (T_X + D).
-- 
R. Kevin Oberman, Network Engineer
E-mail: kob6558 at gmail.com