On Wed, Jul 15, 2020 at 07:35:50AM -0700, Andy Lutomirski wrote: > > On Jul 15, 2020, at 4:12 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > > > <feff>Hi, feff? Are we doing WTF-16 in email now? ;-) > > > > This thread is to discuss the possibility of stracing requests > > submitted through io_uring. I'm not directly involved in io_uring > > development, so I'm posting this out of interest in using strace on > > processes utilizing io_uring. > > > > io_uring gives the developer a way to bypass the syscall interface, > > which results in loss of information when tracing. This is a strace > > fragment on "io_uring-cp" from liburing: > > > > io_uring_enter(5, 40, 0, 0, NULL, 8) = 40 > > io_uring_enter(5, 1, 0, 0, NULL, 8) = 1 > > io_uring_enter(5, 1, 0, 0, NULL, 8) = 1 > > ... > > > > What really happens are read + write requests. Without that > > information the strace output is mostly useless. > > > > This loss of information is not new, e.g. calls through the vdso or > > futext fast paths are also invisible to strace. But losing filesystem > > I/O calls are a major blow, imo. > > > > 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? > > > > Is there some existing tracing infrastructure that strace could use to > > get async completion events? Should we be introducing one? > > > > > > Let’s add some seccomp folks. We probably also want to be able to run seccomp-like filters on io_uring requests. So maybe io_uring should call into seccomp-and-tracing code for each action. Adding Stefano since he had a complementary proposal for iouring restrictions that weren't exactly seccomp.
