Re: syncing the disks when entering sleep

Leisner, Martin
2010-01-22T21:33:17Z

To clarify what I proposed:

if(user sets knobs)
if(disk is spun up)
sync

currently the algorithm is

sync

marty

> -----Original Message-----
> From: Nigel Cunningham [mailto:ncunningham@crca.org.au]
> Sent: Friday, January 22, 2010 4:32 PM
> To: Rafael J. Wysocki
> Cc: Leisner, Martin; linux-pm@lists.linux-foundation.org
> Subject: Re: [linux-pm] syncing the disks when entering sleep
>
> Hi.
>
> Rafael J. Wysocki wrote:
> > On Friday 22 January 2010, Leisner, Martin wrote:
> >> I noticed when we enter sleep states, it seems there's always a
> >> sys_sync given.
> >>
> >> When having an embedded system doing WOL (already in laptop mode to
> >> cache
> >> all the writes), it reasonable to wake up dozens of times of day and
> >> quickly go back to sleep. If the disk is not spun up,
> >> and there's some work to be done, won't the sys_sync spin up the disk
> >> before going to sleep?
> >>
> >> It would be good to have a knob (in /sys) you can tweak from usespace
> to
> >>
> >> configure the behavior of whether you want to do a sync when entering
> >> sleep.
> >>
> >> The ideal behavior would be:
> >>
> >> if(disk is spun up)
> >> then let the sync happen
> >
> > I'm not against that. Patch welcome. :-)
>
> Oooh. I am. That's providing potential for unpredictable behaviour. Much
> better IMO would be providing a tuning know that explicitly and
> unconditionally disables syncing.
>
> Regards,
>
> Nigel