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

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Message-ID: <CAJaqyWdGNfJ3n-E2-PvkuvCiOMsLkEzYaUi5wi-C_n84-a_LAw@mail.gmail.com>
Date: Wed, 7 Aug 2024 15:25:32 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Si-Wei Liu <si-wei.liu@...cle.com>, 
	netdev@...r.kernel.org, linux-rdma@...r.kernel.org, 
	linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev
Subject: Re: [PATCH vhost 0/7] vdpa/mlx5: Parallelize device suspend/resume

On Fri, Aug 2, 2024 at 9:24 AM Dragos Tatulea <dtatulea@...dia.com> 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.
>

There is a missed opportunity processing the CVQ MQ command here,
isn't it? It can be applied on top in another series for sure.

> 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   |
> +-------------------+--------+--------+-----------+
>

Looks great :).

Apart from the nitpick,

Acked-by: Eugenio Pérez <eperezma@...hat.com>

For the vhost part.

Thanks!

> 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.
>
> [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
>