Re: [PATCH 1/1] RDMA/mlx5: Release CPU for other processes in mlx5_free_cmd_msg()

Leon Romanovsky
2024-05-30T17:14:46Z

On Wed, May 22, 2024 at 09:02:56AM +0530, Anand Khoje wrote:
> In non FLR context, at times CX-5 requests release of ~8 million device pages.
> This needs humongous number of cmd mailboxes, which to be released once
> the pages are reclaimed. Release of humongous number of cmd mailboxes
> consuming cpu time running into many secs, with non preemptable kernels
> is leading to critical process starving on that cpu’s RQ. To alleviate
> this, this patch relinquishes cpu periodically but conditionally.
>
> Orabug: 36275016
>
> Signed-off-by: Anand Khoje <anand.a.khoje@oracle.com>
> ---
> drivers/net/ethernet/mellanox/mlx5/core/cmd.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
> index 9c21bce..9fbf25d 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/cmd.c
> @@ -1336,16 +1336,23 @@ static struct mlx5_cmd_msg *mlx5_alloc_cmd_msg(struct mlx5_core_dev *dev,
> return ERR_PTR(err);
> }
>
> +#define RESCHED_MSEC 2
> static void mlx5_free_cmd_msg(struct mlx5_core_dev *dev,
> struct mlx5_cmd_msg *msg)
> {
> struct mlx5_cmd_mailbox *head = msg->next;
> struct mlx5_cmd_mailbox *next;
> + unsigned long start_time = jiffies;
>
> while (head) {
> next = head->next;
> free_cmd_box(dev, head);

Did you consider to make this function asynchronous and parallel?

Thanks

> head = next;
> + if (time_after(jiffies, start_time + msecs_to_jiffies(RESCHED_MSEC))) {
> + mlx5_core_warn_rl(dev, "Spent more than %d msecs, yielding CPU\n", RESCHED_MSEC);
> + cond_resched();
> + start_time = jiffies;
> + }
> }
> kfree(msg);
> }
> --
> 1.8.3.1
>
>