netdev - Re: [PATCH net-next v5 4/5] mvpp2: recycle buffers

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Message-ID: <20210513182048.GA12395@shell.armlinux.org.uk>
Date:   Thu, 13 May 2021 19:20:48 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     netdev@...r.kernel.org, linux-mm@...ck.org,
        Ayush Sawal <ayush.sawal@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Mirko Lindner <mlindner@...vell.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Boris Pismenny <borisp@...dia.com>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
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        Willem de Bruijn <willemb@...gle.com>,
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        Yunsheng Lin <linyunsheng@...wei.com>,
        Guillaume Nault <gnault@...hat.com>,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org,
        bpf@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Eric Dumazet <edumazet@...gle.com>,
        David Ahern <dsahern@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Saeed Mahameed <saeedm@...dia.com>,
        Andrew Lunn <andrew@...n.ch>, Paolo Abeni <pabeni@...hat.com>,
        Sven Auhagen <sven.auhagen@...eatech.de>
Subject: Re: [PATCH net-next v5 4/5] mvpp2: recycle buffers

On Thu, May 13, 2021 at 06:58:45PM +0200, Matteo Croce wrote:
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index b2259bf1d299..9dceabece56c 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -3847,6 +3847,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
>  	struct mvpp2_pcpu_stats ps = {};
>  	enum dma_data_direction dma_dir;
>  	struct bpf_prog *xdp_prog;
> +	struct xdp_rxq_info *rxqi;
>  	struct xdp_buff xdp;
>  	int rx_received;
>  	int rx_done = 0;
> @@ -3912,15 +3913,15 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
>  		else
>  			frag_size = bm_pool->frag_size;
>  
> +		if (bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE)
> +			rxqi = &rxq->xdp_rxq_short;
> +		else
> +			rxqi = &rxq->xdp_rxq_long;
>  
> +		if (xdp_prog) {
> +			xdp.rxq = rxqi;
>  
> +			xdp_init_buff(&xdp, PAGE_SIZE, rxqi);
>  			xdp_prepare_buff(&xdp, data,
>  					 MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM,
>  					 rx_bytes, false);
> @@ -3964,7 +3965,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
>  		}
>  
>  		if (pp)
> +			skb_mark_for_recycle(skb, virt_to_page(data), pp);
>  		else
>  			dma_unmap_single_attrs(dev->dev.parent, dma_addr,
>  					       bm_pool->buf_size, DMA_FROM_DEVICE,

Looking at the above, which I've only quoted the _resulting_ code after
your patch above, I don't see why you have moved the
"bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE" conditional outside of
the test for xdp_prog - I don't see rxqi being used except within that
conditional. Please can you explain the reasoning there?

Thanks.

-- 
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