linux-kernel - Re: Disk spin down issue on shut down/suspend to disk

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Message-Id: <200708092346.13118.rjw@sisk.pl>
Date:	Thu, 9 Aug 2007 23:46:12 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Tejun Heo <htejun@...il.com>
Cc:	Maciej Rutecki <maciej.rutecki@...il.com>,
	Michael Sedkowski <sedmich@...il.com>, trenn@...e.de,
	Robert Hancock <hancockr@...w.ca>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: Disk spin down issue on shut down/suspend to disk

On Wednesday, 8 August 2007 14:24, Rafael J. Wysocki wrote:
> On Wednesday, 8 August 2007 04:56, Tejun Heo wrote:
> > Rafael J. Wysocki wrote:
> > > Well, on my box (nx6325) with the appended (experimental) patch applied
> > > on top of 2.6.23-rc1 with the patchset from
> > > http://www.sisk.pl/kernel/hibernation_and_suspend/2.6.23-rc2/patches/ , the
> > > double spin down doesn't occur during hibernation and the system is shut down
> > > notceably faster.
> > 
> > Can you please explain what the patch does?
> 
> It replaces the shutting down of devices done by kernel_shutdown_prepare()
> with the suspending of the (just like before entering S3, but the target state
> is now S4) and the shutting down of sysdevs with suspending them.
> 
> It also disables the nonboot CPUs before entering the sleep state (S4), which
> generally always is a good idea.
> 
> In short, it makes hibernation_platform_enter() execute the enter-a-sleep-state
> sequence instead of the mixed shutdown-with-entering-S4 thing.
> 
> > So, I take it that entering S4 also spins down the disk.
> 
> Yes.
> 
> > Does the patch remove the ACPI spin down or libata one?
> 
> I _think_ that it removes the ACPI one, although I'll need to do some more
> testing to confirm that.

OK

I can confirm that the patch removes the ACPI spin down (ie. the one that
happens in the power down phase without the patch).

Greetings,
Rafael
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