netdev - Re: [PATCH bpf-next 4/4] ixgbe, xsk: use XSK_NAPI

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Date:   Mon, 7 Sep 2020 12:32:41 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        bpf@...r.kernel.org,
        Björn Töpel <bjorn.topel@...el.com>,
        magnus.karlsson@...el.com, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH bpf-next 4/4] ixgbe, xsk: use XSK_NAPI_WEIGHT as NAPI
 poll budget

On Mon,  7 Sep 2020 17:02:17 +0200 Björn Töpel wrote:
> From: Björn Töpel <bjorn.topel@...el.com>
> 
> Start using XSK_NAPI_WEIGHT as NAPI poll budget for the AF_XDP Rx
> zero-copy path.
> 
> Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> index 3771857cf887..f32c1ba0d237 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> @@ -239,7 +239,7 @@ int ixgbe_clean_rx_irq_zc(struct ixgbe_q_vector *q_vector,
>  	bool failure = false;
>  	struct sk_buff *skb;
>  
> -	while (likely(total_rx_packets < budget)) {
> +	while (likely(total_rx_packets < XSK_NAPI_WEIGHT)) {

I was thinking that we'd multiply 'budget' here, not replace it with a
constant. Looks like ixgbe dutifully passes 'per_ring_budget' into the
clean_rx functions, not a complete NAPI budget.

>  		union ixgbe_adv_rx_desc *rx_desc;
>  		struct ixgbe_rx_buffer *bi;
>  		unsigned int size;