On Wed, May 07, 2014 at 12:53:11PM +0200, Brendan Hide wrote: > On 2014/05/07 09:59 AM, Marc MERLIN wrote: > >[snip] > > > >Did I get this right? > >I'm not sure I did, since it seems the bigger the -dusage number, the > >more work balance has to do. > > > >If I asked -dsuage=85, it would do all chunks that are more than 15% > >full? > > -dusage=85 balances all chunks that up to 85% full. The higher the > number, the more work that needs to be done.
Aah, right. I see why it's more work. =20 only makes is process the few chunks that are up to 20% full which won't be many if your FS is almost full. > Doing a simulation with randomly-semi-filled chunks, "df" at 55%, > and chunk utilisation at 86%, -dusage=55 balances 30% of the chunks, > almost perfectly bringing chunk utilisation down to 56%. In my Oh good, so my guess of using the same number for FS used and dusage= was good, glad to know it worked well for you too. > Pathological use-cases still apply however (for example if all > chunks except one are exactly 54% full). The up-side is that if the > algorithm is applied regularly (as in scripted and scheduled) then > the situation will always be that the majority of chunks are going > to be relatively full, avoiding the pathological use-case. Sounds good. Also, the filesystem itself should ideally do this in the background soon. What we're doing here is just a stopgap. Marc -- "A mouse is a device used to point at the xterm you want to type in" - A.S.R. Microsoft is to operating systems .... .... what McDonalds is to gourmet cooking Home page: http://marc.merlins.org/ | PGP 1024R/763BE901 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html