On Tue, May 14, 2013 at 11:16:55AM -0700, Darrick J. Wong wrote: > On Tue, May 14, 2013 at 02:44:53PM +0100, Joe Thornber wrote: > > On Mon, May 13, 2013 at 11:23:04PM +0200, Pierre Beck wrote: > > > Maybe I'm misunderstanding how the heuristics work - what makes mq > > > pick a block for promotion? > > > > Hi Pierre, > > > > The mq policy is indeed very picky. The first thing I'd suggest is > > you pick up my latest patches if you haven't already: > > > > http://device-mapper.org/patches/3.10/ > > Hm, it looks like all but two of the dmcache patches are in. The two patches > to mq aren't (yet) there. y, unfortunately there's a fixme in there that frightened Alasdair, and I don't have any free capacity to spend on dm-cache atm. > > If you start with a discarded device (eg, you've run mkfs). Then the > > cache should fill up v. quickly with my latest patches. Perhaps it > > would be worth verifying this before you start investigating the > > effects of sequential io? > > I'm also curious about what happens if, say, you have a discard-enabled > zerofree that can "discard" just the unallocated blocks. That probably only > helps if you can discard pieces big enough to fit one of dmcache's discard > regions, right? Yep. But your fs will be trying to reduce fragmentation of free space, so hopefully the pieces will be big enough. - Joe -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
