On Fri, Aug 02, 2024 at 09:14:28AM -0400, Michael S. Tsirkin wrote:

On Fri, Aug 02, 2024 at 10:20:17AM +0300, Dragos Tatulea wrote:

quoted

This series parallelizes the mlx5_vdpa device suspend and resume
operations through the firmware async API. The purpose is to reduce live
migration downtime.

The series starts with changing the VQ suspend and resume commands
to the async API. After that, the switch is made to issue multiple
commands of the same type in parallel.

Finally, a bonus improvement is thrown in: keep the notifierd enabled
during suspend but make it a NOP. Upon resume make sure that the link
state is forwarded. This shaves around 30ms per device constant time.

For 1 vDPA device x 32 VQs (16 VQPs), on a large VM (256 GB RAM, 32 CPUs
x 2 threads per core), the improvements are:

+-------------------+--------+--------+-----------+
| operation         | Before | After  | Reduction |
|-------------------+--------+--------+-----------|
| mlx5_vdpa_suspend | 37 ms  | 2.5 ms |     14x   |
| mlx5_vdpa_resume  | 16 ms  | 5 ms   |      3x   |
+-------------------+--------+--------+-----------+

Note for the maintainers:
The first patch contains changes for mlx5_core. This must be applied
into the mlx5-vhost tree [0] first. Once this patch is applied on
mlx5-vhost, the change has to be pulled from mlx5-vdpa into the vhost
tree and only then the remaining patches can be applied.

Or maintainer just acks it and I apply directly.

We can do it, but there is a potential to create a conflict between your tree
and netdev for whole cycle, which will be a bit annoying. Easiest way to avoid
this is to have a shared branch, but in august everyone is on vacation, so it
will be probably fine to apply such patch directly.

Thanks

Let me know when all this can happen.

quoted

[0] https://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux.git/log/?h=mlx5-vhost

Dragos Tatulea (7):
  net/mlx5: Support throttled commands from async API
  vdpa/mlx5: Introduce error logging function
  vdpa/mlx5: Use async API for vq query command
  vdpa/mlx5: Use async API for vq modify commands
  vdpa/mlx5: Parallelize device suspend
  vdpa/mlx5: Parallelize device resume
  vdpa/mlx5: Keep notifiers during suspend but ignore

 drivers/net/ethernet/mellanox/mlx5/core/cmd.c |  21 +-
 drivers/vdpa/mlx5/core/mlx5_vdpa.h            |   7 +
 drivers/vdpa/mlx5/net/mlx5_vnet.c             | 435 +++++++++++++-----
 3 files changed, 333 insertions(+), 130 deletions(-)

-- 
2.45.2