On Mon, 23 Aug 2010 04:23:59 pm Wu Fengguang wrote: > On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote: > > On Fri, 20 Aug 2010 15:50:54 +1000 > > > > Con Kolivas <kernel@xxxxxxxxxxx> wrote: > > > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote: > > > > > The dirty_ratio was silently limited to >= 5%. This is not a user > > > > > expected behavior. Let's rip it. > > > > > > > > > > It's not likely the user space will depend on the old behavior. > > > > > So the risk of breaking user space is very low. > > > > > > > > > > CC: Jan Kara <jack@xxxxxxx> > > > > > CC: Neil Brown <neilb@xxxxxxx> > > > > > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > > > > > > > Thank you. > > > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > > > > > > I have tried to do this in the past, and setting this value to 0 on > > > some machines caused the machine to come to a complete standstill with > > > small writes to disk. It seemed there was some kind of "minimum" amount > > > of data required by the VM before anything would make it to the disk > > > and I never quite found out where that blockade occurred. This was some > > > time ago (3 years ago) so I'm not sure if the problem has since been > > > fixed in the VM since then. I suggest you do some testing with this > > > value set to zero before approving this change. > > You are right, vm.dirty_ratio=0 will block applications for ever.. Indeed. And while you shouldn't set the lower limit to zero to avoid this problem, it doesn't answer _why_ this happens. What is this "minimum write" that blocks everything, will 1% be enough, and is it hiding another real bug somewhere in the VM? Regards, Con -- -ck -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>