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Message-ID: <20200108145322.GA2975@apalos.home>
Date: Wed, 8 Jan 2020 16:53:22 +0200
From: Ilias Apalodimas <ilias.apalodimas@...aro.org>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: netdev@...r.kernel.org, brouer@...hat.com, davem@...emloft.net,
lorenzo.bianconi@...hat.com
Subject: Re: [PATCH] net: socionext: get rid of huge dma sync in
netsec_alloc_rx_data
Hi Lorenzo,
On Tue, Jan 07, 2020 at 04:30:32PM +0100, Lorenzo Bianconi wrote:
> Socionext driver can run on dma coherent and non-coherent devices.
> Get rid of huge dma_sync_single_for_device in netsec_alloc_rx_data since
> now the driver can let page_pool API to managed needed DMA sync
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> drivers/net/ethernet/socionext/netsec.c | 45 +++++++++++++++----------
> 1 file changed, 28 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c
> index b5a9e947a4a8..00404fef17e8 100644
> --- a/drivers/net/ethernet/socionext/netsec.c
> +++ b/drivers/net/ethernet/socionext/netsec.c
> @@ -243,6 +243,7 @@
> NET_IP_ALIGN)
> #define NETSEC_RX_BUF_NON_DATA (NETSEC_RXBUF_HEADROOM + \
> SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))
> +#define NETSEC_RX_BUF_SIZE (PAGE_SIZE - NETSEC_RX_BUF_NON_DATA)
>
> #define DESC_SZ sizeof(struct netsec_de)
>
> @@ -719,7 +720,6 @@ static void *netsec_alloc_rx_data(struct netsec_priv *priv,
> {
>
> struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
> - enum dma_data_direction dma_dir;
> struct page *page;
>
> page = page_pool_dev_alloc_pages(dring->page_pool);
> @@ -734,9 +734,7 @@ static void *netsec_alloc_rx_data(struct netsec_priv *priv,
> /* Make sure the incoming payload fits in the page for XDP and non-XDP
> * cases and reserve enough space for headroom + skb_shared_info
> */
> - *desc_len = PAGE_SIZE - NETSEC_RX_BUF_NON_DATA;
> - dma_dir = page_pool_get_dma_dir(dring->page_pool);
> - dma_sync_single_for_device(priv->dev, *dma_handle, *desc_len, dma_dir);
> + *desc_len = NETSEC_RX_BUF_SIZE;
>
> return page_address(page);
> }
> @@ -883,6 +881,7 @@ static u32 netsec_xdp_xmit_back(struct netsec_priv *priv, struct xdp_buff *xdp)
> static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> struct xdp_buff *xdp)
> {
> + struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
> u32 ret = NETSEC_XDP_PASS;
> int err;
> u32 act;
> @@ -896,7 +895,10 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> case XDP_TX:
> ret = netsec_xdp_xmit_back(priv, xdp);
> if (ret != NETSEC_XDP_TX)
> - xdp_return_buff(xdp);
> + __page_pool_put_page(dring->page_pool,
> + virt_to_head_page(xdp->data),
> + xdp->data_end - xdp->data_hard_start,
Do we have to include data_hard_start?
@Jesper i know bpf programs can modify the packet, but isn't it safe
to only sync for xdp->data_end - xdp->data in this case since the DMA transfer
in this driver will always start *after* the XDP headroom?
> + true);
> break;
> case XDP_REDIRECT:
> err = xdp_do_redirect(priv->ndev, xdp, prog);
> @@ -904,7 +906,10 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> ret = NETSEC_XDP_REDIR;
> } else {
> ret = NETSEC_XDP_CONSUMED;
> - xdp_return_buff(xdp);
> + __page_pool_put_page(dring->page_pool,
> + virt_to_head_page(xdp->data),
> + xdp->data_end - xdp->data_hard_start,
Ditto
> + true);
> }
> break;
> default:
> @@ -915,7 +920,10 @@ static u32 netsec_run_xdp(struct netsec_priv *priv, struct bpf_prog *prog,
> /* fall through -- handle aborts by dropping packet */
> case XDP_DROP:
> ret = NETSEC_XDP_CONSUMED;
> - xdp_return_buff(xdp);
> + __page_pool_put_page(dring->page_pool,
> + virt_to_head_page(xdp->data),
> + xdp->data_end - xdp->data_hard_start,
Ditto
> + true);
> break;
> }
>
> @@ -1014,7 +1022,8 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget)
> * cache state. Since we paid the allocation cost if
> * building an skb fails try to put the page into cache
> */
> - page_pool_recycle_direct(dring->page_pool, page);
> + __page_pool_put_page(dring->page_pool, page,
> + desc->len, true);
I think you can sync for pkt_len here only, since that's the area the DMA engine
touched. Syncing for desc->len, will sync the entire area (like the older
version did).
Keep in mind that the driver always starts the DMA transfer after
NETSEC_RXBUF_HEADROOM which is 192 or 256 bytes depending on XDP running or not.
So in the default SKB case if the pkt_len = 60 the
xdp.data_end - xdp.data_hard_start = 316.
I think it's safe here to only sync pkt_len, since noone will touch the XDP
headroom
> netif_err(priv, drv, priv->ndev,
> "rx failed to build skb\n");
> break;
> @@ -1272,17 +1281,19 @@ static int netsec_setup_rx_dring(struct netsec_priv *priv)
> {
> struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];
> struct bpf_prog *xdp_prog = READ_ONCE(priv->xdp_prog);
> - struct page_pool_params pp_params = { 0 };
> + struct page_pool_params pp_params = {
> + .order = 0,
> + /* internal DMA mapping in page_pool */
> + .flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
> + .pool_size = DESC_NUM,
> + .nid = NUMA_NO_NODE,
> + .dev = priv->dev,
> + .dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE,
> + .offset = NETSEC_RXBUF_HEADROOM,
> + .max_len = NETSEC_RX_BUF_SIZE,
> + };
> int i, err;
>
> - pp_params.order = 0;
> - /* internal DMA mapping in page_pool */
> - pp_params.flags = PP_FLAG_DMA_MAP;
> - pp_params.pool_size = DESC_NUM;
> - pp_params.nid = NUMA_NO_NODE;
> - pp_params.dev = priv->dev;
> - pp_params.dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
> -
> dring->page_pool = page_pool_create(&pp_params);
> if (IS_ERR(dring->page_pool)) {
> err = PTR_ERR(dring->page_pool);
> --
> 2.21.1
>
Thanks
/Ilias
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