From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: syncing the disks when entering sleep Date: Fri, 22 Jan 2010 22:35:20 +0100 Message-ID: <201001222235.20474.rjw@sisk.pl> References: <76FA3B279DD9DA48896E2B404944957204E0B241@USA7061MS02.na.xerox.net> <201001222149.46839.rjw@sisk.pl> <4B5A1942.2050003@crca.org.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4B5A1942.2050003@crca.org.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Nigel Cunningham Cc: linux-pm@lists.linux-foundation.org, "Leisner, Martin" List-Id: linux-pm@vger.kernel.org On Friday 22 January 2010, Nigel Cunningham wrote: > 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. You're right, sorry. Yes, a knob that disables syncing unconditionally was the thing I was thinking about. Rafael