Re: [PATCH net-next 05/10] net: hns3: using modulo for cyclic counters in hclge_cmd_send

[David Miller]

From: Peng Li <lipeng321@xxxxxxxxxx>
Date: Fri, 29 Jun 2018 19:23:00 +0800

> @@ -228,8 +228,7 @@ int hclge_cmd_send(struct hclge_hw *hw, struct hclge_desc *desc, int num)
>  		desc_to_use = &hw->cmq.csq.desc[hw->cmq.csq.next_to_use];
>  		*desc_to_use = desc[handle];
>  		(hw->cmq.csq.next_to_use)++;
> -		if (hw->cmq.csq.next_to_use == hw->cmq.csq.desc_num)
> -			hw->cmq.csq.next_to_use = 0;
> +		hw->cmq.csq.next_to_use %= hw->cmq.csq.desc_num;
>  		handle++;

I would advise against this.

The "%" modulus operation takes many cpu cycles, and the current code
is thus much faster.