On Thu, Dec 06, 2018 at 10:11:39AM -0800, Darrick J. Wong wrote: > I think this has the same problem that Dave complained about back in > October -- if I have a hard disk with 512b sectors, a xfs with 4k > blocks, and mount it on a machine with 64k pages, then single-sector > buffers will get a small slab allocation, but single-fsb buffers will > now fall back to grabbing a 64k page to hold 4k worth of data. > > Even if we add a second slab for single-fsb blocks, we'll run into the > same problem if the filesystem contains multi-block directory blocks, so > then we'd potentially need a third slab, and... is there a way to ask a > slab allocator for multiple contiguous objects totalling less than > PAGE_SIZE bytes? No, unfortunately there is not. And the sad part is that generally it will give you aligned ones, just with slub debugging turned on it won't.
