From f19fadfce8717d1da5e38c12d0dbe473bc3a7626 Mon Sep 17 00:00:00 2001 From: willy tarreau Date: Thu, 16 Jan 2014 08:20:17 +0100 Subject: [PATCH] net: mvneta: implement rx_copybreak calling dma_map_single()/dma_unmap_single() is quite expensive compared to copying a small packet. So let's copy short frames and keep the buffers mapped. We set the limit to 256 bytes which seems to give good results both on the XP-GP board and on the AX3/4. The Rx small packet rate increased by 16.4% doing this, from 486kpps to 573kpps. It is worth noting that even the call to the function dma_sync_single_range_for_cpu() is expensive (300 ns) although less than dma_unmap_single(). Without it, the packet rate raises to 711kpps (+24% more). Thus on systems where coherency from device to CPU is guaranteed by a snoop control unit, this patch should provide even more gains, and probably rx_copybreak could be increased. Cc: Thomas Petazzoni Cc: Gregory CLEMENT Tested-by: Arnaud Ebalard Signed-off-by: Willy Tarreau Signed-off-by: David S. Miller --- drivers/net/ethernet/marvell/mvneta.c | 44 +++++++++++++++++++++++---- 1 file changed, 38 insertions(+), 6 deletions(-) diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c index 726a8d292a08..f5fc7a249880 100644 --- a/drivers/net/ethernet/marvell/mvneta.c +++ b/drivers/net/ethernet/marvell/mvneta.c @@ -444,6 +444,8 @@ static int txq_number = 8; static int rxq_def; +static int rx_copybreak __read_mostly = 256; + #define MVNETA_DRIVER_NAME "mvneta" #define MVNETA_DRIVER_VERSION "1.0" @@ -1463,22 +1465,51 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo, rx_done++; rx_filled++; rx_status = rx_desc->status; + rx_bytes = rx_desc->data_size - (ETH_FCS_LEN + MVNETA_MH_SIZE); data = (unsigned char *)rx_desc->buf_cookie; if (!mvneta_rxq_desc_is_first_last(rx_status) || - (rx_status & MVNETA_RXD_ERR_SUMMARY) || - !(skb = build_skb(data, pp->frag_size > PAGE_SIZE ? 0 : pp->frag_size))) { + (rx_status & MVNETA_RXD_ERR_SUMMARY)) { + err_drop_frame: dev->stats.rx_errors++; mvneta_rx_error(pp, rx_desc); /* leave the descriptor untouched */ continue; } - dma_unmap_single(pp->dev->dev.parent, rx_desc->buf_phys_addr, + if (rx_bytes <= rx_copybreak) { + /* better copy a small frame and not unmap the DMA region */ + skb = netdev_alloc_skb_ip_align(dev, rx_bytes); + if (unlikely(!skb)) + goto err_drop_frame; + + dma_sync_single_range_for_cpu(dev->dev.parent, + rx_desc->buf_phys_addr, + MVNETA_MH_SIZE + NET_SKB_PAD, + rx_bytes, + DMA_FROM_DEVICE); + memcpy(skb_put(skb, rx_bytes), + data + MVNETA_MH_SIZE + NET_SKB_PAD, + rx_bytes); + + skb->protocol = eth_type_trans(skb, dev); + mvneta_rx_csum(pp, rx_status, skb); + napi_gro_receive(&pp->napi, skb); + + rcvd_pkts++; + rcvd_bytes += rx_bytes; + + /* leave the descriptor and buffer untouched */ + continue; + } + + skb = build_skb(data, pp->frag_size > PAGE_SIZE ? 0 : pp->frag_size); + if (!skb) + goto err_drop_frame; + + dma_unmap_single(dev->dev.parent, rx_desc->buf_phys_addr, MVNETA_RX_BUF_SIZE(pp->pkt_size), DMA_FROM_DEVICE); - rx_bytes = rx_desc->data_size - - (ETH_FCS_LEN + MVNETA_MH_SIZE); rcvd_pkts++; rcvd_bytes += rx_bytes; @@ -1495,7 +1526,7 @@ static int mvneta_rx(struct mvneta_port *pp, int rx_todo, /* Refill processing */ err = mvneta_rx_refill(pp, rx_desc); if (err) { - netdev_err(pp->dev, "Linux processing - Can't refill\n"); + netdev_err(dev, "Linux processing - Can't refill\n"); rxq->missed++; rx_filled--; } @@ -2945,3 +2976,4 @@ module_param(rxq_number, int, S_IRUGO); module_param(txq_number, int, S_IRUGO); module_param(rxq_def, int, S_IRUGO); +module_param(rx_copybreak, int, S_IRUGO | S_IWUSR); -- 2.39.5