On 4/27/20 12:22 PM, Jann Horn wrote: > On Mon, Apr 27, 2020 at 5:56 PM Jens Axboe <axboe@xxxxxxxxx> wrote: >> On 4/27/20 9:40 AM, Clay Harris wrote: >>> I was excited to see IORING_OP_SPLICE go in, but disappointed that tee >>> didn't go in at the same time. It would be very useful to copy pipe >>> buffers in an async program. >> >> Pavel, care to wire up tee? From a quick look, looks like just exposing >> do_tee() and calling that, so should be trivial. > > Just out of curiosity: > > What's the purpose of doing that via io_uring? Non-blocking sys_tee() > just shoves around some metadata, it doesn't do any I/O, right? Is > this purely for syscall-batching reasons? (And does that mean that you > would also add syscalls like epoll_wait() and futex() to io_uring?) Or > is this because you're worried about blocking on the pipe mutex? Right, it doesn't do any IO. It does potentially block on the inode mutex, but that's about it. I think the reasons are mainly: - Keep the interfaces the same, instead of using both sync and async calls. - Bundling/batch reasons, either in same submission, or chained. Some folks have talked about futex, and epoll_wait would also be a natural extension as well, since we already have the ctl part. -- Jens Axboe
