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Message-ID: <1516569725.42536.99.camel@freebsd.org>
Subject: Re: Periodical interrupt storm when playing game with USB keyboard
From: Ian Lepore <ian@freebsd.org>
To: Hans Petter Selasky <hps@selasky.org>, Johannes Lundberg
 <johalun0@gmail.com>
Cc: freebsd-current <freebsd-current@freebsd.org>
Date: Sun, 21 Jan 2018 14:22:05 -0700
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On Sun, 2018-01-21 at 22:07 +0100, Hans Petter Selasky wrote:
> On 01/21/18 21:45, Johannes Lundberg wrote:
> > 
> > What does kern.eventtimer.periodic do?  The sysctl description
> > wasn't
> > that elaborate...
> It turns off re-programming the timer every time there is a new
> callout 
> with earlier completion time.
> 
> --HPS

Well, it does more than that.  It makes the system run "the old way"
where there are periodic timer interrupts that happen whether they need
to or not (bad for power saving), and there's no way to schedule
anything to happen on intervals other than when the periodic ticks
occur (so if kern.hz = 1000 and you ask to sleep for a microsecond you
may actually sleep up to a millisecond).

-- Ian