On Tue, Jan 11, 2022 at 1:00 PM Richard W.M. Jones <[email protected]> wrote: > > On Tue, Jan 11, 2022 at 08:07:39AM +0100, Laszlo Ersek wrote: > > hmmmm, not necessarily; according to the manual, "qemu-img convert" uses > > (by default) 8 co-routines. There's also the -W flag ("out of order > > writes"), which I don't know if the original virt-v2v used. > > I'm never sure how qemu coroutines map to threads. I assume it's not > 1-1, and it's somehow connected to the iothread setting?
In qemu-img and qemu-nbd, when using cache=none and aio=native there is one thread submitting io via libaio. When using aio=threads we can see multiple threads doing the I/O. I don't know how qemu maps request to threads, but it seems that we have one thread per inflight request, but never more than 16 (qmu-nbd never handle more than 16 inflight requests per client). I tested with "nbdcopy --connections 1 --requests ..." and we see the same number of threads in qemu-nbd plus one idle thread when requests < 16. Nir _______________________________________________ Libguestfs mailing list [email protected] https://listman.redhat.com/mailman/listinfo/libguestfs
