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

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Date:	Wed, 08 Aug 2007 11:35:32 -0400
From:	Mark Lord <liml@....ca>
To:	unlisted-recipients:; (no To-header on input)
Cc:	Tejun Heo <htejun@...il.com>,
	Michael Sedkowski <sedmich@...il.com>, trenn@...e.de,
	Robert Hancock <hancockr@...w.ca>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	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

Mark Lord wrote:
>
> My suspend script now has this little chunk of code at the point
> where it actually does the suspend-to-RAM:
> 
>    sync; sync
>    hdparm -F /dev/sda   ## flush drive write cache
>    sleep 1              ## allow time for the flush to complete
>    echo mem > /sys/power/state  ## suspend-to-RAM
> 
> Without the "sleep 1", it doesn't always eliminate the extra Retract,
> so I hypothesize that the FLUSH_CACHE_EXT command is implemented in
> an asynchronous fashion by the drive:  it returns immediately before
> it has actually completed writing cached data to disk.  The "sleep 1"
> seems to give it enough time to finish up, at least for me.

Further to this, if I have an active-writer running at the time of suspend,
then even my scripted "sleep 1" is not good enough, as additional writes
are still happening before/after the flush.

Now I'll reboot and try it with the "sleep 1" hardcoded inside sd_suspend().

Cheers
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