Internships/ProjectIdeas/FUSEUringCmd

FUSE-over-io_uring exports

Expected outcome: Extend QEMU's FUSE export type with FUSE-over-io_uring support

FUSE-over-io_uring is a new high-performance interface for Filesystem in Userspace (FUSE) servers. The FUSE kernel code has added uring_cmd support so that FUSE servers can send and receive data directly over io_uring instead of reading/writing from/to the FUSE device. This reduces the number of system calls, as well as allowing for batching and polling, so that CPU overhead should be reduced.

QEMU's FUSE export type presents a file containing the contents of a disk image. This is a convenient way of using tools like fdisk(1) or dd(1) on a non-raw disk image file, like qcow2, that these tools would otherwise not be able to operate on. The current FUSE export implementation uses libfuse's FUSE device file descriptor handling APIs (fuse_session_fd(), fuse_session_receive_buf(), etc) to read(2)/write(2) in the traditional way.

Your task is to add FUSE-over-io_uring support as an alternative mode on systems where FUSE-over-io_uring is available.

Tasks:

• Integrate FUSE-over-io_uring mode into the QEMU FUSE export
• Add support for multiple in-flight requests
• Benchmark with and without FUSE-over-io_uring using the fio(1) tool
• Add support support multiple IOThreads

Links:

• QEMU FUSE export code
• libfuse branch with FUSE-over-io_uring support
• Overview of low-level FUSE-over-io_uring interface (handled by libfuse, but good background info)

Details:

• Project size: 350 hours
• Skill level: intermediate
• Language: C
• Mentors: Kevin Wolf (kwolf@redhat.com), Stefan Hajnoczi (stefanha@redhat.com)