On Tue, Nov 17 2009 at 11:12am -0500, Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > s->store->type->prepare_merge returns the number of chunks that can be > linearly copied starting from the returned chunk number backward. (but > the caller is allowed to copy less, and the caller puts the number of > copied chunks to s->store->type->commit_merge) > > I.e. if returned chunk numbers are old_chunk == 10 and new_chunk == 20 > and returned value is 3, then chunk 20 can be copied to 10, chunk 19 to > 9 and 18 to 8. > > s->merge_write_interlock_n has now been allowed to be increased up to > the full range of chunks returned from s->store->type->prepare_merge. > Until now kcopyd was only ever allowed to copy one chunk at a time; > as a result snapshot-merge performance was extremely slow. > > Also, snapshot_merge_process() needs to delay the merging of _all_ > chunks that have in-progress writes; not just the first chunk in the > region that is to be merged. > > snapshot-merge performance is now very respectible. s/respectible/respectable/ Also, I removed the following from the patch header but it helps show how "respectable" snapshot-merge performance is with this patch: Here are performance results from some mkfs-based testing: # lvcreate -n testlv -L 32G test # lvcreate -n testlv_snap -s -L 7G test/testlv # time mkfs.ext3 /dev/test/testlv ... real 1m7.827s user 0m0.116s sys 0m11.017s # lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert testlv test owi-a- 32.00G testlv_snap test swi-a- 7.00G testlv 9.05 before: ------- # time lvconvert --merge test/testlv_snap Merging of volume testlv_snap started. ... Merge into logical volume testlv finished. Logical volume "snapshot1" successfully removed real 22m33.100s user 0m0.045s sys 0m0.711s after: ------ # time lvconvert --merge test/testlv_snap Merging of volume testlv_snap started. testlv: Merged: 6.4% testlv: Merged: 3.5% testlv: Merged: 0.9% testlv: Merged: 0.0% Merge into logical volume testlv finished. Logical volume "snapshot1" successfully removed real 1m0.881s user 0m0.015s sys 0m0.560s -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
