Re: [Qemu-devel] [RFC PATCH 00/17] COarse-grain LOck-stepping(COLO) Virtual Machines for Non-stop Service

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Yang Hongyang (yanghy@cn.fujitsu.com) wrote:
> Virtual machine (VM) replication is a well known technique for
> providing application-agnostic software-implemented hardware fault
> tolerance "non-stop service". COLO is a high availability solution.
> Both primary VM (PVM) and secondary VM (SVM) run in parallel. They
> receive the same request from client, and generate response in parallel
> too. If the response packets from PVM and SVM are identical, they are
> released immediately. Otherwise, a VM checkpoint (on demand) is
> conducted. The idea is presented in Xen summit 2012, and 2013,
> and academia paper in SOCC 2013. It's also presented in KVM forum
> 2013:
> http://www.linux-kvm.org/wiki/images/1/1d/Kvm-forum-2013-COLO.pdf
> Please refer to above document for detailed information. 
> Please also refer to previous posted RFC proposal:
> http://lists.nongnu.org/archive/html/qemu-devel/2014-06/msg05567.html

Hi Yang,
  Thanks for this set of patches (and I've replied to many individually).

> The patchset is also hosted on github:
> https://github.com/macrosheep/qemu/tree/colo_v0.1
> 
> This patchset is RFC, implements the frame of colo, without
> failover and nic/disk replication. But it is ready for demo
> the COLO idea above QEMU-Kvm.
> Steps using this patchset to get an overview of COLO:
> 1. configure the source with --enable-colo option
> 2. compile
> 3. just like QEMU's normal migration, run 2 QEMU VM:
>    - Primary VM 
>    - Secondary VM with -incoming tcp:[IP]:[PORT] option
> 4. on Primary VM's QEMU monitor, run following command:
>    migrate_set_capability colo on
>    migrate tcp:[IP]:[PORT]
> 5. done
> you will see two runing VMs, whenever you make changes to PVM, SVM
> will be synced to PVM's state.
> 
> TODO list:
> 1. failover
> 2. nic replication
> 3. disk replication[COLO Disk manager]

I wonder if there are any parts that can be borrowed from other code
to get it going; I notice that the reverse execution patchset
has a network packet record/replay mode:

https://lists.gnu.org/archive/html/qemu-devel/2014-07/msg00157.html

What was used for the nic comparison in the 2013 kvm forum paper?

Dave

> 
> Any comments/feedbacks are warmly welcomed.
> 
> Thanks,
> Yang
> 
> Yang Hongyang (17):
>   configure: add CONFIG_COLO to switch COLO support
>   COLO: introduce an api colo_supported() to indicate COLO support
>   COLO migration: add a migration capability 'colo'
>   COLO info: use colo info to tell migration target colo is enabled
>   COLO save: integrate COLO checkpointed save into qemu migration
>   COLO restore: integrate COLO checkpointed restore into qemu restore
>   COLO buffer: implement colo buffer as well as QEMUFileOps based on it
>   COLO: disable qdev hotplug
>   COLO ctl: implement API's that communicate with colo agent
>   COLO ctl: introduce is_slave() and is_master()
>   COLO ctl: implement colo checkpoint protocol
>   COLO ctl: add a RunState RUN_STATE_COLO
>   COLO ctl: implement colo save
>   COLO ctl: implement colo restore
>   COLO save: reuse migration bitmap under colo checkpoint
>   COLO ram cache: implement colo ram cache on slaver
>   HACK: trigger checkpoint every 500ms
> 
>  Makefile.objs                      |   2 +
>  arch_init.c                        | 174 +++++++++-
>  configure                          |  14 +
>  include/exec/cpu-all.h             |   1 +
>  include/migration/migration-colo.h |  36 +++
>  include/migration/migration.h      |  13 +
>  include/qapi/qmp/qerror.h          |   3 +
>  migration-colo-comm.c              |  78 +++++
>  migration-colo.c                   | 643 +++++++++++++++++++++++++++++++++++++
>  migration.c                        |  45 ++-
>  qapi-schema.json                   |   9 +-
>  stubs/Makefile.objs                |   1 +
>  stubs/migration-colo.c             |  34 ++
>  vl.c                               |  12 +
>  14 files changed, 1044 insertions(+), 21 deletions(-)
>  create mode 100644 include/migration/migration-colo.h
>  create mode 100644 migration-colo-comm.c
>  create mode 100644 migration-colo.c
>  create mode 100644 stubs/migration-colo.c
> 
> -- 
> 1.9.1
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK