RE: [PATCH 0/6] refactor RDMA live migration based on rsocket API

["Gonglei (Arei)" via <qemu-devel@nongnu.org>]

> -----Original Message-----
> From: Jinpu Wang [mailto:jinpu.wang@ionos.com]
> Sent: Friday, June 7, 2024 1:54 PM
> To: Gonglei (Arei) <arei.gonglei@huawei.com>
> Cc: qemu-devel@nongnu.org; peterx@redhat.com; yu.zhang@ionos.com;
> mgalaxy@akamai.com; elmar.gerdes@ionos.com; zhengchuan
> <zhengchuan@huawei.com>; berrange@redhat.com; armbru@redhat.com;
> lizhijian@fujitsu.com; pbonzini@redhat.com; mst@redhat.com; Xiexiangyou
> <xiexiangyou@huawei.com>; linux-rdma@vger.kernel.org; lixiao (H)
> <lixiao91@huawei.com>; Wangjialin <wangjialin23@huawei.com>
> Subject: Re: [PATCH 0/6] refactor RDMA live migration based on rsocket API
> 
> Hi Gonglei, hi folks on the list,
> 
> On Tue, Jun 4, 2024 at 2:14 PM Gonglei <arei.gonglei@huawei.com> wrote:
> >
> > From: Jialin Wang <wangjialin23@huawei.com>
> >
> > Hi,
> >
> > This patch series attempts to refactor RDMA live migration by
> > introducing a new QIOChannelRDMA class based on the rsocket API.
> >
> > The /usr/include/rdma/rsocket.h provides a higher level rsocket API
> > that is a 1-1 match of the normal kernel 'sockets' API, which hides
> > the detail of rdma protocol into rsocket and allows us to add support
> > for some modern features like multifd more easily.
> >
> > Here is the previous discussion on refactoring RDMA live migration
> > using the rsocket API:
> >
> > https://lore.kernel.org/qemu-devel/20240328130255.52257-1-philmd@linar
> > o.org/
> >
> > We have encountered some bugs when using rsocket and plan to submit
> > them to the rdma-core community.
> >
> > In addition, the use of rsocket makes our programming more convenient,
> > but it must be noted that this method introduces multiple memory
> > copies, which can be imagined that there will be a certain performance
> > degradation, hoping that friends with RDMA network cards can help verify,
> thank you!
> First thx for the effort, we are running migration tests on our IB fabric, different
> generation of HCA from mellanox, the migration works ok, there are a few
> failures,  Yu will share the result later separately.
> 

Thank you so much. 

> The one blocker for the change is the old implementation and the new rsocket
> implementation; they don't talk to each other due to the effect of different wire
> protocol during connection establishment.
> eg the old RDMA migration has special control message during the migration
> flow, which rsocket use a different control message, so there lead to no way to
> migrate VM using rdma transport pre to the rsocket patchset to a new version
> with rsocket implementation.
> 
> Probably we should keep both implementation for a while, mark the old
> implementation as deprecated, and promote the new implementation, and
> high light in doc, they are not compatible.
> 

IMO It makes sense. What's your opinion? @Peter.


Regards,
-Gonglei

> Regards!
> Jinpu
> 
> 
> 
> >
> > Jialin Wang (6):
> >   migration: remove RDMA live migration temporarily
> >   io: add QIOChannelRDMA class
> >   io/channel-rdma: support working in coroutine
> >   tests/unit: add test-io-channel-rdma.c
> >   migration: introduce new RDMA live migration
> >   migration/rdma: support multifd for RDMA migration
> >
> >  docs/rdma.txt                     |  420 ---
> >  include/io/channel-rdma.h         |  165 ++
> >  io/channel-rdma.c                 |  798 ++++++
> >  io/meson.build                    |    1 +
> >  io/trace-events                   |   14 +
> >  meson.build                       |    6 -
> >  migration/meson.build             |    3 +-
> >  migration/migration-stats.c       |    5 +-
> >  migration/migration-stats.h       |    4 -
> >  migration/migration.c             |   13 +-
> >  migration/migration.h             |    9 -
> >  migration/multifd.c               |   10 +
> >  migration/options.c               |   16 -
> >  migration/options.h               |    2 -
> >  migration/qemu-file.c             |    1 -
> >  migration/ram.c                   |   90 +-
> >  migration/rdma.c                  | 4205 +----------------------------
> >  migration/rdma.h                  |   67 +-
> >  migration/savevm.c                |    2 +-
> >  migration/trace-events            |   68 +-
> >  qapi/migration.json               |   13 +-
> >  scripts/analyze-migration.py      |    3 -
> >  tests/unit/meson.build            |    1 +
> >  tests/unit/test-io-channel-rdma.c |  276 ++
> >  24 files changed, 1360 insertions(+), 4832 deletions(-)  delete mode
> > 100644 docs/rdma.txt  create mode 100644 include/io/channel-rdma.h
> > create mode 100644 io/channel-rdma.c  create mode 100644
> > tests/unit/test-io-channel-rdma.c
> >
> > --
> > 2.43.0
> >