Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio

[Wu Fengguang <fengguang.wu@intel.com>]

On Fri, Aug 20, 2010 at 01:50:54PM +0800, Con Kolivas 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@suse.cz>
> > > CC: Neil Brown <neilb@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> >
> > Thank you.
> > 	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> 
> 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.

Good point. I'll do more homework. Thanks for the reminding!

Thanks,
Fengguang