On Tue, Jun 11, 2019 at 10:57 AM Stefan Hajnoczi <stefa...@redhat.com> wrote: > On Mon, Jun 10, 2019 at 07:18:53PM +0530, Aarushi Mehta wrote: > > This patch series adds support for the newly developed io_uring Linux AIO > > interface. Linux io_uring is faster than Linux's AIO asynchronous I/O code, > > offers efficient buffered asynchronous I/O support, the ability to do I/O > > without performing a system call via polled I/O, and other efficiency > > enhancements. > > > > Testing it requires a host kernel (5.1+) and the liburing library. > > Use the option -drive aio=io_uring to enable it. > > > > v5: > > - Adds completion polling > > - Extends qemu-io > > - Adds qemu-iotest > > Flush is not hooked up. Please use the io_uring IOURING_OP_FSYNC that > you've already written and connect it to file-posix.c.
IOURING_OP_FSYNC is in fact synchronous. This means io_uring_enter() blocks until this operation completes. This is not desirable since the AIO engine should not block the QEMU thread it's running from for a long time (e.g. network file system that is not responding). I think it's best *not* to use io_uring for fsync. Instead we can continue to use the thread pool, just like Linux AIO. Stefan
