Am 19.09.2017 um 16:41 schrieb Paolo Bonzini: > On 19/09/2017 15:36, Peter Lieven wrote: >> Hi, >> >> I just noticed that CPU throttling and Block Migration don't work >> together very well. >> During block migration the throttling heuristic detects that we >> obviously make no progress >> in ram transfer. But the reason is the running block migration and not a >> too high dirty pages rate. >> >> The result is that any VM is throttled by 99% during block migration. >> >> I wonder what the best way would be fix this. I came up with the >> following ideas so far: >> >> - disable throttling while block migration is in bulk stage >> - check if absolute number of num_dirty_pages_period crosses a threshold >> and not if its just >> greater than 50% of transferred bytes >> - check if migration_dirty_pages > 0. This slows down throttling, but >> does not avoid it completely. > If you can use nbd-server and drive-mirror for block migration (libvirt > would do it), then you will use multiple sockets and be able to migrate > block and RAM at the same time. > > Otherwise, disabling throttling during the bulk stage is the one that > seems nicest and most promising.
Okay, but this can be done independently of the nbd approach. If someone uses classic block migration and auto converge his vserver will freeze. I will send a patch to fix that. Thanks, Peter
