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Date: Mon, 5 May 2014 10:53:45 +0200
From: Fabian Keil <freebsd-listen@fabiankeil.de>
To: "freebsd-acpi@freebsd.org" <freebsd-acpi@freebsd.org>
Subject: Re: proposal: set default lid state to S3, performance/economy Cx
 states to Cmax
Message-ID: <20140505105345.099e4503@fabiankeil.de>
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Warren Block <wblock@wonkity.com> wrote:

> On Sun, 4 May 2014, Adrian Chadd wrote:

> > The easy-to-run test is "sysctl dev.cpu.0.cx_lowest=3DCmax" and then us=
e stuff.
>=20
> It's that "use stuff" step that would preferably be automated.  Is the=20
> failure mode a lockup, or could a program detect problems?  The idea=20
> is to get lots of feedback, fast.

One possible failure mode is that timers tick unreliably which can be
detected automatically (in some cases), for example by using the DTrace
script timestamp-test.d:
http://www.fabiankeil.de/gehacktes/dtrace-timestamp-tests/

It should also be possible to let the kernel do this itself
and log an error message and maybe optionally disable Cx
states that cause problems:
sysctl dev.cpu.0.cx_lowest=3DCmax-as-long-as-it-appears-to-be-working

Fabian

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