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Date:      Fri, 19 Nov 2010 13:24:02 +0200
From:      Alexander Motin <mav@FreeBSD.org>
To:        Bruce Cran <bruce@cran.org.uk>
Cc:        Alexander Best <arundel@freebsd.org>, Tijl Coosemans <tijl@coosemans.org>, Oliver Fromme <olli@lurza.secnetix.de>, freebsd-hackers@freebsd.org, Dag-Erling@FreeBSD.ORG
Subject:   Re: Summary: Re: Spin down HDD after disk sync or before power off
Message-ID:  <4CE65E52.5040009@FreeBSD.org>
In-Reply-To: <20101119111557.00000a3a@unknown>
References:  <201009161742.24228.tijl@coosemans.org>	<201009161619.o8GGJAmv035378@lurza.secnetix.de>	<20101018155944.GA12425@freebsd.org>	<868w1r92rf.fsf@ds4.des.no>	<20101021122110.GA65490@freebsd.org>	<4CC156F5.1050109@FreeBSD.org>	<20101022100309.GA16446@freebsd.org>	<20101116204000.00005aea@unknown> <20101119111557.00000a3a@unknown>

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Bruce Cran wrote:
> On Tue, 16 Nov 2010 20:40:00 +0000
> Bruce Cran <bruce@cran.org.uk> wrote:
> 
>> One problem with the code that's been committed is that the shutdown
>> event handler doesn't get run during a suspend operation so an
>> emergency unload still gets done when running "acpiconf -s3".
> 
> Something else I noticed today: I've just got a new disk that supports
> NCQ and found the kern.cam.ada.ada_send_ordered sysctl that appears to
> enable/disable its use (?).  

ada_send_ordered controls periodical non-queued commands insertion to
avoid possible infinite commands starvation and timeouts as result. NCQ
can't be disabled now.

> But the shutdown handler that spins
> the disk down only gets initialized if ada_send_ordered is enabled. I
> was wondering what the reason for this is?

Interesting question. That code came as-is from "da" driver and I can't
explain it. I have feeling that it's wrong.

-- 
Alexander Motin



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