> -----Original Message----- > From: Rafael J. Wysocki [mailto:rjw@xxxxxxx] > Sent: Wednesday, February 10, 2010 5:34 AM > To: linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx > Cc: Pavel Machek; Nigel Cunningham; Leisner, Martin > Subject: Re: syncing the disks when entering sleep > > On Wednesday 10 February 2010, Pavel Machek wrote: > > > Hi. > > > > > > Pavel Machek wrote: > > > >> So you're asking to give this knob "one shot behavior" (i.e. > "then > > > >> next sleep won't sync")? > > > > > > > > Yes. > > > > > > > >> But I'm primarily interested in the behavior on embedded systems > > > >> (where you control all the processes running -- there's no "user" > > > >> involved. > > > >> > > > > > > > > Well, then "one shot behaviour" does not hurt you, right? > > > > > > > >> If a user starts messing with default settings, any unwanted > > > >> behavior is the users problem (besides, this should only be > > > >> writable as root). > > > >> > > > > > > > > I'd rather not add traps for the user unless absolutely > neccessary. > > > > Not even for root user. Pavel > > > > > > But that's precisely what you're doing. You're advocating making the > > > behaviour inconsistent. If what you're suggesting is done, you won't > be > > > able to simply cat the sysfs entry to know whether sys_syncing is > going > > > to be done on the next cycle. You'll also have to have knowledge of > > > whether a cycle has been done since the last time the value is set. > The > > > end result will be someone getting trapped and caught out because > they > > > think '1' in /sys/power/dont_sync (or whatever it's called) means > what > > > it says. > > > > I'm simply advocating that setting from one suspend should not change > > other suspends ... because you have multiple different programs > > wanting to suspend the system, all independend. > > Which is wrong. There should be one power manager everybody else calls > to > suspend the system. Yes, even if the battery is running critical. > > And I guess on the embedded systems in question the situation is exactly > like > that. > > > See the example about system running low on battery earlier in the > thread. > > Which is irrelevant here. > > Actually, doing the sync() in the kernel is a hack that we decided not > to > remove just because the users space didin't do the right thing on some > systems. > If the user space always synced disks before suspending, we wouldn't > have to > do that in the kernel. > > Same goes for the kernel VT switch, BTW. > > So really, I don't see anything wrong with a knob that will turn the > kernel > sync off entirely, because that basically means "my user space is not > broken". > > Rafael This is interesting. When I saw the sync's I said to myself "WTF?" It definitely should be a knob because it implements policy behavior -- which is often detrimental to power saving efforts. marty _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
