linux-kernel - Re: [PATCH] mlx5: simplify EQ interrupt polling logic

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Message-ID: <469dfbf5-4b5f-4457-8f88-f180b2c3a8ae@gmail.com>
Date: Thu, 24 Oct 2024 19:59:34 +0300
From: Tariq Toukan <ttoukan.linux@...il.com>
To: Caleb Sander Mateos <csander@...estorage.com>,
 Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 Tariq Toukan <tariqt@...dia.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mlx5: simplify EQ interrupt polling logic



On 23/10/2024 23:51, Caleb Sander Mateos wrote:
> Use a while loop in mlx5_eq_comp_int() and mlx5_eq_async_int() to
> clarify the EQE polling logic. This consolidates the next_eqe_sw() calls
> for the first and subequent iterations. It also avoids a goto. Turn the
> num_eqes < MLX5_EQ_POLLING_BUDGET check into a break condition.
> 
> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/eq.c | 22 +++++++-------------
>   1 file changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> index 68cb86b37e56..859dcf09b770 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> @@ -114,15 +114,11 @@ static int mlx5_eq_comp_int(struct notifier_block *nb,
>   	struct mlx5_eq *eq = &eq_comp->core;
>   	struct mlx5_eqe *eqe;
>   	int num_eqes = 0;
>   	u32 cqn = -1;
>   
> -	eqe = next_eqe_sw(eq);
> -	if (!eqe)
> -		goto out;
> -
> -	do {
> +	while ((eqe = next_eqe_sw(eq))) {
>   		struct mlx5_core_cq *cq;
>   
>   		/* Make sure we read EQ entry contents after we've
>   		 * checked the ownership bit.
>   		 */
> @@ -140,13 +136,14 @@ static int mlx5_eq_comp_int(struct notifier_block *nb,
>   					    "Completion event for bogus CQ 0x%x\n", cqn);
>   		}
>   
>   		++eq->cons_index;
>   
> -	} while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = next_eqe_sw(eq)));
> +		if (++num_eqes >= MLX5_EQ_POLLING_BUDGET)
> +			break;
> +	}
>   
> -out:
>   	eq_update_ci(eq, 1);
>   
>   	if (cqn != -1)
>   		tasklet_schedule(&eq_comp->tasklet_ctx.task);
>   
> @@ -213,15 +210,11 @@ static int mlx5_eq_async_int(struct notifier_block *nb,
>   	eqt = dev->priv.eq_table;
>   
>   	recovery = action == ASYNC_EQ_RECOVER;
>   	mlx5_eq_async_int_lock(eq_async, recovery, &flags);
>   
> -	eqe = next_eqe_sw(eq);
> -	if (!eqe)
> -		goto out;
> -
> -	do {
> +	while ((eqe = next_eqe_sw(eq))) {
>   		/*
>   		 * Make sure we read EQ entry contents after we've
>   		 * checked the ownership bit.
>   		 */
>   		dma_rmb();
> @@ -229,13 +222,14 @@ static int mlx5_eq_async_int(struct notifier_block *nb,
>   		atomic_notifier_call_chain(&eqt->nh[eqe->type], eqe->type, eqe);
>   		atomic_notifier_call_chain(&eqt->nh[MLX5_EVENT_TYPE_NOTIFY_ANY], eqe->type, eqe);
>   
>   		++eq->cons_index;
>   
> -	} while ((++num_eqes < MLX5_EQ_POLLING_BUDGET) && (eqe = next_eqe_sw(eq)));
> +		if (++num_eqes >= MLX5_EQ_POLLING_BUDGET)
> +			break;
> +	}
>   
> -out:
>   	eq_update_ci(eq, 1);
>   	mlx5_eq_async_int_unlock(eq_async, recovery, &flags);
>   
>   	return unlikely(recovery) ? num_eqes : 0;
>   }

LGTM.
Reviewed-by: Tariq Toukan <tariqt@...dia.com>

Thanks.