Hi Miklos, A performance regression is observed since linux v4.19 when we do aio test using fio with iodepth 128 on overlayfs. And we found that queue depth of the device is always 1 which is unexpected. After investigation, it is found that commit 16914e6fc7 (“ovl: add ovl_read_iter()”) and commit 2a92e07edc (“ovl: add ovl_write_iter()”) use do_iter_readv_writev() to submit requests to real filesystem. Async IOs are converted to sync IOs here and cause performance regression. I wondered that is this a design flaw or supposed to be. Thanks a lot, Jiufei
