On Tue, Dec 22 2020 at 8:32am -0500, Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote: > On Mon, Dec 14, 2020 at 07:00:57PM -0800, Palmer Dabbelt wrote: > > I haven't gotten a whole lot of feedback, so I'm inclined to at least have some > > reasonable performance numbers before bothering with a v2. > > FYI, my other main worry beside duplicating nbd is that device mapper > really is a stacked interface that sits on top of other block device. > Turning this into something else that just pipes data to userspace > seems very strange. I agree. Only way I'd be interested is if it somehow tackled enabling much more efficient IO. Earlier discussion in this thread mentioned that zero-copy and low overhead wasn't a priority (because it is hard, etc). But the hard work has already been done with io_uring. If dm-user had a prereq of leaning heavily on io_uring and also enabled IO polling for bio-based then there may be a win to supporting it. But unless lower latency (or some other more significant win) is made possible I just don't care to prop up an unnatural DM bolt-on. Mike
