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.