* Daniel P. Berrangé (berra...@redhat.com) wrote: > On Mon, Apr 12, 2021 at 03:51:10PM +0100, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berra...@redhat.com) wrote: > > > On Thu, Apr 08, 2021 at 08:11:54PM +0100, Dr. David Alan Gilbert (git) > > > wrote: > > > > From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > > > > > > > Hi, > > > > This RFC set adds support for multipath TCP (mptcp), > > > > in particular on the migration path - but should be extensible > > > > to other users. > > > > > > > > Multipath-tcp is a bit like bonding, but at L3; you can use > > > > it to handle failure, but can also use it to split traffic across > > > > multiple interfaces. > > > > > > > > Using a pair of 10Gb interfaces, I've managed to get 19Gbps > > > > (with the only tuning being using huge pages and turning the MTU up). > > > > > > > > It needs a bleeding-edge Linux kernel (in some older ones you get > > > > false accept messages for the subflows), and a C lib that has the > > > > constants defined (as current glibc does). > > > > > > > > To use it you just need to append ,mptcp to an address; > > > > > > > > -incoming tcp:0:4444,mptcp > > > > migrate -d tcp:192.168.11.20:4444,mptcp > > > > > > What happens if you only enable mptcp flag on one side of the > > > stream (whether client or server), does it degrade to boring > > > old single path TCP, or does it result in an error ? > > > > I've just tested this and it matches what pabeni said; it seems to just > > fall back. > > > > > > I had a quick go at trying NBD as well, but I think it needs > > > > some work with the parsing of NBD addresses. > > > > > > In theory this is applicable to anywhere that we use sockets. > > > Anywhere that is configured with the QAPI SocketAddress / > > > SocketAddressLegacy type will get it for free AFAICT. > > > > That was my hope. > > > > > Anywhere that is configured via QemuOpts will need an enhancement. > > > > > > IOW, I would think NBD already works if you configure NBD via > > > QMP with nbd-server-start, or block-export-add. qemu-nbd will > > > need cli options added. > > > > > > The block layer clients for NBD, Gluster, Sheepdog and SSH also > > > all get it for free when configured va QMP, or -blockdev AFAICT > > > > Have you got some examples via QMP? > > I'd failed trying -drive > > if=virtio,file=nbd://192.168.11.20:3333,mptcp=on/zero > > I never remember the mapping to blockdev QAPI schema, especially > when using legacy filename syntax with the URI. > > Try instead > > -blockdev driver=nbd,host=192.168.11.20,port=3333,mptcp=on,id=disk0backend > -device virtio-blk,drive=disk0backend,id=disk0
That doesn't look like the right syntax, but it got me closer; and it's working with no more code changes: On the source: qemu... -nographic -M none -drive if=none,file=my.qcow2,id=mydisk (qemu) nbd_server_start 0.0.0.0:3333,mptcp=on (qemu) nbd_server_add -w mydisk On the destination: -blockdev driver=nbd,server.type=inet,server.host=192.168.11.20,server.port=3333,server.mptcp=on,node-name=nbddisk,export=mydisk -device virtio-blk,drive=nbddisk,id=disk0 and it succesfully booted off it, and it looks like it has two flows. (It didn't get that great a bandwidth, but I'm not sure where that's due to). Dave > > > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
