Timing issue with Dummynet on high kernel timer interrupt

[Bruce Evans]

On Sat, 7 Nov 2015, Hans Petter Selasky wrote:

> On 11/07/15 07:19, Bruce Evans wrote:
>> I don't know if CTLFLAG_RWTUN with SYSCTL_PROC() actually works for all
>> types, but it is used with CTLFLAG_STRING for kern.corefile.  This is
>> another bogus undocumented tunable.  It is better documented as a sysctl
>> than most since it is old so it is documented in sysctl(8).  It is not
>> documented as a tunable there of course.  It is also not documented as
>> a tunable in core(5).
>
> SYSCTL_PROC() works with RWTUN from /boot/loader.conf, as long as the 
> procedure callback handles early calls during boot.

Hmm, that would be messy if it wants to do hardware stuff like
sysctl_kern_eventtimer_periodic() does.

Timercounters only have 1 MI tunable
(sysctl_kern_timecounter_adjprecision).  It has a (cold) check to avoid
doing too much.

Bruce