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From: John Baldwin <jhb@freebsd.org>
To: freebsd-current@freebsd.org
Cc: Rick Macklem <rmacklem@uoguelph.ca>, Adrian Chadd <adrian.chadd@gmail.com>,
 Alexander Kabaev <kabaev@gmail.com>
Subject: Re: slow screen updates on laptop console (i386)
Date: Tue, 08 Dec 2015 10:41:05 -0800
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On Monday, December 07, 2015 06:01:08 PM Rick Macklem wrote:
> Adrian Chadd wrote:
> > Hi,
> > 
> > ok. please file a bug for that. It may be something to do with the
> > hardware and sleep states and skipping wakeups/interrupts or
> > something.
> > 
> > Please try using the default again (LAPIC?) and set
> > kern.eventtimer.periodic=1. See if that fixes it.
> > 
> Actually made it worse. Instead of being intermittently slow, it was
> almost constantly slow.

Try disabling C-states if they are enabled.  If you have a BIOS option
for C1E you might need to disable that as well.  If this fixes it, then
there isn't a really viable solution in software, and you might prefer
to use the RTC to get the power savings from C-states.

-- 
John Baldwin