On Wed, Jul 15, 2020 at 9:43 PM Pavel Begunkov <asml.sile...@gmail.com> wrote: > > To clear details for those who are not familiar with io_uring: > > io_uring has a pair of queues, submission (SQ) and completion queues (CQ), > both shared between kernel and user spaces. The userspace submits requests > by filling a chunk of memory in SQ. The kernel picks up SQ entries in > (syscall io_uring_enter) or asynchronously by polling SQ. > > CQ entries are filled by the kernel completely asynchronously and > in parallel. Some users just poll CQ to get them, but also have a way > to wait for them. > > >>> > >>> What do people think? > >>> > >>> From what I can tell, listing the submitted requests on > >>> io_uring_enter() would not be hard. Request completion is > >>> asynchronous, however, and may not require io_uring_enter() syscall. > >>> Am I correct? > > Both, submission and completion sides may not require a syscall.
Okay. > >>> Is there some existing tracing infrastructure that strace could use to > >>> get async completion events? Should we be introducing one? > > There are static trace points covering all needs. This needs to be unprivileged, or its usefulness is again compromized. > > And if not used the whole thing have to be zero-overhead. Otherwise > there is perf, which is zero-overhead, and this IMHO won't fly. Obviously it needs to be zero overhead if not tracing. What won't fly? Thanks, Miklos
