On Thu, Aug 05, 2021 at 03:38:01PM +0100, David Howells wrote: > Generally, I prefer to write back the minimum I can get away with (as does the > Linux NFS client AFAICT). > > However, if everyone agrees that we should only ever write back a multiple of > a certain block size, even to network filesystems, what block size should that > be? Note that PAGE_SIZE varies across arches and folios are going to > exacerbate this. What I don't want to happen is that you read from a file, it > creates, say, a 4M (or larger) folio; you change three bytes and then you're > forced to write back the entire 4M folio. grep . /sys/class/block/*/queue/minimum_io_size and also hw_sector_size, logical_block_size, physical_block_size. The data seems suspect to me, though. I get 4096 for a spinner (looks sane), 512 for nvme (less than page size), and 4096 for pmem (I'd expect cacheline or ECC block). Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢠⠒⠀⣿⡁ ⢿⡄⠘⠷⠚⠋⠀ Certified airhead; got the CT scan to prove that! ⠈⠳⣄⠀⠀⠀⠀
