On Fri, May 31, 2024 at 07:15:34AM -0700, Christoph Hellwig wrote: > On Fri, May 31, 2024 at 07:12:10AM -0700, Darrick J. Wong wrote: > > There are <cough> some users that want 1G extents. > > > > For the rest of us who don't live in the stratosphere, it's convenient > > for fsdax to have rt extents that match the PMD size, which could be > > large on arm64 (e.g. 512M, or two smr sectors). > > That's fine. Maybe to rephrase my question. With this series we > have 3 different truncate path: > > 1) unmap all blocks (!rt || rtextsizse == 1) > 2) zero leftover blocks in an rtextent (small rtextsize, but > 1) > 3) converted leftover block in an rtextent to unwritten (large > rtextsize) > > What is the right threshold to switch between 2 and 3? And do we > really need 2) at all? I don't think we need (2) at all. There's likely some threshold below where it's a wash -- compare with ext4 strategy of trying to write 64k chunks even if that requires zeroing pagecache to cut down on fragmentation on hdds -- but I don't know if we care anymore. ;) --D
