On Wed, 18 Dec 2019, Joe Thornber wrote: > On Sun, Dec 15, 2019 at 09:44:49PM +0000, Eric Wheeler wrote: > > I was looking through the dm-bio-prison-v2 commit for dm-cache (b29d4986d) > > and it is huge, ~5k lines. Do you still have a git branch with these > > commits in smaller pieces (not squashed) so we can find the bits that > > might be informative for converting lv-thin to use dm-bio-prison-v2? > > > > For example, I think that, at least, the policy changes and > > btracker code is dm-cache specific and just a distraction when trying to > > understand the dm-bio-prison-v2 conversion. > > To be honest I would hold off for a couple of months. I've been working > on the design for thinp 2 and have got to the point where I need to write > a userland proof of concept implementation. In particular I've focussed on > packing more into btree nodes, and separating transactions so IO to different > thins has no locking contention. The proof of concept will tell me just how > small I can get the metadata. If the level of metadata compression is ~1/10th > we'll plug the new btrees into the existing design and switch to bio prison > v2. > If it's greater, say 1/50th, then I'll rewrite the whole target to > use write-ahead logging for transactionality and ditch all metadata sharing > altogether. > When the metadata is that small we can copy entire btrees to implement > snapshots.
Sounds great, looking forward to it. The thinp target has worked great for us over the years. Packing metadata and reducing lock contention will make it even better. -- Eric Wheeler > > - Joe > > -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
