[libvirt] [PATCH 0/6] Post-copy live migration support

[Cristian Klein]

Qemu currently implements pre-copy live migration. VM memory pages are
first copied from the source hypervisor to the destination, potentially
multiple times as pages get dirtied during transfer, then VCPU state
is migrated. Unfortunately, if the VM dirties memory faster than the
network bandwidth, then pre-copy cannot finish. `virsh` currently
includes an option to suspend a VM after a timeout, so that migration
may finish, but at the expense of downtime.

A future version of qemu will implement post-copy live migration. The
VCPU state is first migrated to the destination hypervisor, then
memory pages are pulled from the source hypervisor. Post-copy has the
potential to do migration with zero-downtime, despite the VM dirtying
pages fast, with minimum performance impact. On the other hand, one
post-copy is in progress, any network failure would render the VM
unusable, as its memory is partitioned between the source and
destination hypervisor. Therefore, post-copy should only be used when
necessary.

Post-copy migration in qemu will work as follows:
(1) The `x-postcopy-ram` migration capability needs to be set.
(2) Migration is started.
(3) When the user decides so, post-copy migration is activated by
sending the `migrate-start-postcopy` command. Qemu acknowledges by
setting migration status to `postcopy-active`.

Cristian Klein (6):
  Added qemu postcopy-active migration status
  Added public API to enable post-copy migration
  Added new public API virDomainMigrateStartPostCopy
  Added domainMigrateStartPostCopy in qemu driver
  Added domainMigrateStartPostCopy in remote driver
  virsh: added migrate --postcopy-after

 include/libvirt/libvirt.h.in |  3 ++
 src/driver.h                 |  4 +++
 src/libvirt.c                | 44 +++++++++++++++++++++++++++
 src/libvirt_public.syms      |  5 +++
 src/qemu/qemu_driver.c       | 44 +++++++++++++++++++++++++++
 src/qemu/qemu_migration.c    | 44 +++++++++++++++++++++++++++
 src/qemu/qemu_migration.h    |  3 +-
 src/qemu/qemu_monitor.c      | 21 ++++++++++++-
 src/qemu/qemu_monitor.h      |  3 ++
 src/qemu/qemu_monitor_json.c | 21 ++++++++++++-
 src/qemu/qemu_monitor_json.h |  1 +
 src/qemu/qemu_monitor_text.c | 14 ++++++++-
 src/qemu/qemu_monitor_text.h |  2 ++
 src/remote/remote_driver.c   |  1 +
 src/remote/remote_protocol.x | 12 +++++++-
 tools/virsh-domain.c         | 72 ++++++++++++++++++++++++++++++++++++++++++--
 tools/virsh.pod              |  5 +++
 17 files changed, 292 insertions(+), 7 deletions(-)

-- 
1.9.1