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Re: [Qemu-devel] [PATCH 0/12 RFC v2] Localhost migration
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 0/12 RFC v2] Localhost migration |
Date: |
Fri, 26 Jul 2013 11:41:38 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 |
Il 25/07/2013 22:18, Lei Li ha scritto:
> Hi,
>
> This patch series tries to add localhost migration support to
> Qemu.
>
> When doing localhost 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
> migration.
>
> Following I copied from last version that Anthony added for the
> benefit of the other reviewers:
>
> The goal here is to allow "live upgrade" of a running QEMU instance.
> The work flow would look like this:
>
> 1) Guests are running QEMU release 1.6.1
> 2) Admin installs QEMU release 1.6.2 via RPM or deb
> 3) Admin does localhost migration with page flipping to use new version
> of QEMU.
>
> Page flipping is used in order to avoid requiring that there is enough
> free memory to fit an additional copy of the largest guest which is the
> requirement today with localhost migration.
>
> You can also read from the link below:
> http://lists.gnu.org/archive/html/qemu-devel/2013-06/msg02577.html
>
> 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 implemented 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.
>
> Now it's still a draft version, and as it is implemented separately
> to the current migration code for a easy start, the next step will
> be trying to integrate it into the current migration implementation
> closely. To make sure we are on the right direction that should be
> headed, please let me know your suggestions on this.
>
> For the interface, as Anthony has suggested using a flag or a
> capability, which one would you prefer or any ideas?
Using a capability on the source makes sense; I don't think anything
special is needed on the destination. The destination just sees a
special packet telling it that a pipe is available via SCM_RIGHTS; then
it fetches the file descriptor and uses it for the new protocol.
It looks like this could reuse a lot of the RAM copying hooks that we
introduced for RDMA. You shouldn't need to change anything in savevm.c
or arch_init.c
Paolo
> Your comments are very welcome!
>
> TODO:
> - Integrate to the current implement of migration closely?
> - Introduce a mechanism to exchange a PIPE via SCM_RIGHTS.
> - benchmark/evaluation.
>
> Lei Li (12):
> migration: export MIG_STATE_xxx flags
> savevm: export qemu_save_device_state()
> rename is_active to is_block_active
> arch_init: introduce ram_page_save()
> arch_init: introduce ram_save_local()
> arch_init: add save_local_setup to savevm_ram_handlers
> savevm: introduce qemu_savevm_local()
> savevm: adjust is_ram check in register_savevm_live()
> migration-local: implementation of outgoing part
> migration-local: implementation 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 | 110 +++++++++++++++++++
> block-migration.c | 2 +-
> hmp-commands.hx | 17 ++++
> hmp.c | 13 +++
> hmp.h | 1 +
> include/migration/migration.h | 32 +++++++
> include/sysemu/sysemu.h | 1 +
> migration-local.c | 228
> +++++++++++++++++++++++++++++++++++++++++
> migration-unix.c | 60 ++++++++++++
> migration.c | 8 --
> qapi-schema.json | 14 +++
> qemu-options.hx | 9 ++
> qmp-commands.hx | 22 +++++
> savevm.c | 100 +++++++++++++++--
> vl.c | 14 +++
> 16 files changed, 613 insertions(+), 19 deletions(-)
> create mode 100644 migration-local.c
>
- [Qemu-devel] [PATCH 02/12] savevm: export qemu_save_device_state(), (continued)
- [Qemu-devel] [PATCH 02/12] savevm: export qemu_save_device_state(), Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 05/12] arch_init: introduce ram_save_local(), Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 06/12] arch_init: add save_local_setup to savevm_ram_handlers, Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 07/12] savevm: introduce qemu_savevm_local(), Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 08/12] savevm: adjust is_ram check in register_savevm_live(), Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 01/12] migration: export MIG_STATE_xxx flags, Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 12/12] hmp: add hmp_localhost_migration interface, Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 10/12] migration-local: implementation of incoming part, Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 09/12] migration-local: implementation of outgoing part, Lei Li, 2013/07/25
- [Qemu-devel] [PATCH 11/12] migration-local: add option to commandline for incoming-local, Lei Li, 2013/07/25
- Re: [Qemu-devel] [PATCH 0/12 RFC v2] Localhost migration,
Paolo Bonzini <=