Subject: Re: [PATCH vhost 0/7] vdpa/mlx5: Parallelize device suspend/resume

From: "Michael S. Tsirkin" <[email-masked]>
Date: Fri, 2 Aug 2024 09:14:28 -0400

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

Let me know when all this can happen.

> [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