[Qemu-devel] [PATCH 0/7 RFC] Localhost live migration

[Lei Li]

Hi,

This patch series tries to add localhost live migration support
to Qemu. It is just a draft version which is far from completing
and I am still working on, send it out to have your suggestions
and make sure it is the way should be headed. Your comments are
very appreciated!

When doing localhost live migration, the host memory will balloon
up during the period, might consume double memories for some time.
So we want to add a new live migration mechanism localhost live 
migration.

The plan is:

1) Add new command to do localhost migration.

   The qmp interface introduced like:

   { 'command': 'localhost-migrate', 'data': {'uri': 'str'} }

2) Use different mechanism than current live migration.

   The very basic work flow like:

       qemu on the source (the source and destination are both on localhost)
              |
              V
           Stop VM
              |
              V   
          Create threads
              |
              V
       Page flipping through vmspice
              |
              V
       MADV_DONTNEED the ram pages which are already flipped
              |
              V
       Migration completes

   As stopping VM first, we expect/resume the page flipping through vmspice
   is fast enough to meet *live migration (low downtime).

Notes:
Currently the work flow is not exactly the same as description
above. For the first step, the work flow we plan to implement is:
stop VM and copy ram pages via unix domain socket, MADV_DONTNEED 
ram pages that already copied. After that, will replace to vmsplice
mechanism instead of copying pages.

TODO:
- Working on the completing of ram copy and MADV_DONTNEED part.
- Introduce a mechanism to exchange a PIPE via SCM_RIGHTS.
- benchmark/evaluation.

Lei Li (7):
  migration: export MIG_STATE_xxx flags
  savevm: export qemu_save_device_state()
  arch_init: add ram_madvise_free()
  migration-local: implementation of outgoing part
  migration-local: impelementation of incoming part
  migration-local: add option to command line for local incoming
  hmp:add hmp_localhost_migration interface


 Makefile.objs                 |    1 +
 arch_init.c                   |   13 ++++
 hmp-commands.hx               |   17 +++++
 hmp.c                         |   13 ++++
 hmp.h                         |    1 +
 include/migration/migration.h |   32 +++++++++
 include/sysemu/sysemu.h       |    1 +
 migration-local.c             |  155 +++++++++++++++++++++++++++++++++++++++++
 migration-unix.c              |   60 ++++++++++++++++
 migration.c                   |    8 --
 qapi-schema.json              |   14 ++++
 qemu-options.hx               |    9 +++
 qmp-commands.hx               |   22 ++++++
 savevm.c                      |    2 +-
 vl.c                          |   14 ++++
 15 files changed, 353 insertions(+), 9 deletions(-)
 create mode 100644 migration-local.c