On 3/3/23 9:57 PM, Alexander Larsson wrote: > On Mon, Feb 27, 2023 at 10:22 AM Alexander Larsson <alexl@xxxxxxxxxx> wrote: > > * Erofs on top of direct-io enabled loopback causes quite a drop in > performance, which I don't really understand. Especially since its > reporting the same memory use as non-direct io. I guess the > double-cacheing in the later case isn't properly attributed to the > cgroup so the difference is not measured. However, why would the > double cache improve performance? Maybe I'm not completely > understanding how these things interact. > Loop in BUFFERED mode actually calls .read_iter() of the backing file to read from it, e.g. ext4_file_read_iter()->generic_file_read_iter(), where heuristic readahead is also done. -- Thanks, Jingbo
