On Thu, Apr 21, 2022 at 18:08:36 +0100, Daniel P. Berrangé wrote: > On Thu, Apr 14, 2022 at 09:54:16AM +0200, Claudio Fontana wrote: > > RFC, starting point for discussion. > > > > Sketch API changes to allow parallel Saves, and open up > > and implementation for QEMU to leverage multifd migration to files, > > with optional multifd compression. > > > > This allows to improve save times for huge VMs. > > > > The idea is to issue commands like: > > > > virsh save domain /path/savevm --parallel --parallel-connections 2 > > > > and have libvirt start a multifd migration to: > > > > /path/savevm : main migration connection > > /path/savevm.1 : multifd channel 1 > > /path/savevm.2 : multifd channel 2 > > At a conceptual level the idea would to still have a single file, > but have threads writing to different regions of it. I don't think Note that guys from Virtuozzo planned to do enhancements to the migration code which would allow post-copy style migration into a file. For this they need a memory image with "random access" especially for the loading part. Now the idea was to use a different image format, something more like a qcow2 container (or actually a qcow2 image) to store the memory pages but allow random access. Now with that a parallel output could also theoretically be possible IIRC. Unfortunately I have no idea how their work is progressing, it was a while ago already we've discussed it here.
