On Tue, Jun 19 2012 at 10:44am -0400, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > On Tue, Jun 19 2012 at 9:52am -0400, > Spelic <spelic@xxxxxxxxxxxxx> wrote: > > > I do not know what is the mechanism for which xfs cannot unmap > > blocks from dm-thin, but it really can't. > > If anyone has dm-thin installed he can try. This is 100% > > reproducible for me. > > I was initially surprised by this considering the thinp-test-suite does > test a compilebench workload against xfs and ext4 using online discard > (-o discard). > > But I just modified that test to use a thin-pool with 'ignore_discard' > and the test still passed on both ext4 and xfs. > > So there is more work needed in the thinp-test-suite to use blktrace > hooks to verify that discards are occuring when the compilebench > generated files are removed. > > I'll work through that and report back. blktrace shows discards for both xfs and ext4. But in general xfs is issuing discards with much smaller extents than ext4 does, e.g.: to the thin device: + 128 vs + 32 to the thin-pool's data device: + 120 vs + 16 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
