Re: [Libguestfs] Benchmarks of asynch nbdublk (was: Re: [PATCH libnbd] ublk: Add new nbdublk program)

On Sun, Aug 28, 2022 at 04:39:07PM +0100, Richard W.M. Jones wrote: BTW we had a GSoC student last summer who was supposed to work on adding io_uring support to libnbd. Unfortunately they didn't complete the assignment (or start it, to be honest). We would still like to add it to libnbd in future. However libnbd implements a network protocol and while io_uring would certainly overcome the syscall KPTI overhead, there's still the basic problem that unlike block I/O, network I/O has dependencies between requests - you cannot execute them out of order - so although it'll have some benefit I don't think it'll make a huge difference. (Be interesting to find out whether or not I'm right about this.) Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com nbdkit - Flexible, fast NBD server with plugins https://gitlab.com/nbdkit/nbdkit