enic: 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.

Signed-off-by: Govindarajulu Varadarajan <_govind@gmx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/cisco/enic/enic.h b/drivers/net/ethernet/cisco/enic/enic.h
index 962510f..5ba5ad0 100644 (file)
--- a/drivers/net/ethernet/cisco/enic/enic.h
+++ b/drivers/net/ethernet/cisco/enic/enic.h
@@ -186,6 +186,7 @@ struct enic {
        ____cacheline_aligned struct vnic_cq cq[ENIC_CQ_MAX];
        unsigned int cq_count;
        struct enic_rfs_flw_tbl rfs_h;
+       u32 rx_copybreak;
 };
 
 static inline struct device *enic_get_dev(struct enic *enic)

diff --git a/drivers/net/ethernet/cisco/enic/enic_main.c b/drivers/net/ethernet/cisco/enic/enic_main.c
index c8832bc..929bfe7 100644 (file)
--- a/drivers/net/ethernet/cisco/enic/enic_main.c
+++ b/drivers/net/ethernet/cisco/enic/enic_main.c
@@ -66,6 +66,8 @@
 #define PCI_DEVICE_ID_CISCO_VIC_ENET_DYN     0x0044  /* enet dynamic vnic */
 #define PCI_DEVICE_ID_CISCO_VIC_ENET_VF      0x0071  /* enet SRIOV VF */
 
+#define RX_COPYBREAK_DEFAULT           256
+
 /* Supported devices */
 static const struct pci_device_id enic_id_table[] = {
        { PCI_VDEVICE(CISCO, PCI_DEVICE_ID_CISCO_VIC_ENET) },
@@ -924,6 +926,7 @@ static void enic_free_rq_buf(struct vnic_rq *rq, struct vnic_rq_buf *buf)
        pci_unmap_single(enic->pdev, buf->dma_addr,
                buf->len, PCI_DMA_FROMDEVICE);
        dev_kfree_skb_any(buf->os_buf);
+       buf->os_buf = NULL;
 }
 
 static int enic_rq_alloc_buf(struct vnic_rq *rq)
@@ -934,7 +937,24 @@ static int enic_rq_alloc_buf(struct vnic_rq *rq)
        unsigned int len = netdev->mtu + VLAN_ETH_HLEN;
        unsigned int os_buf_index = 0;
        dma_addr_t dma_addr;
+       struct vnic_rq_buf *buf = rq->to_use;
+
+       if (buf->os_buf) {
+               buf = buf->next;
+               rq->to_use = buf;
+               rq->ring.desc_avail--;
+               if ((buf->index & VNIC_RQ_RETURN_RATE) == 0) {
+                       /* Adding write memory barrier prevents compiler and/or
+                        * CPU reordering, thus avoiding descriptor posting
+                        * before descriptor is initialized. Otherwise, hardware
+                        * can read stale descriptor fields.
+                        */
+                       wmb();
+                       iowrite32(buf->index, &rq->ctrl->posted_index);
+               }
 
+               return 0;
+       }
        skb = netdev_alloc_skb_ip_align(netdev, len);
        if (!skb)
                return -ENOMEM;
@@ -957,6 +977,25 @@ static void enic_intr_update_pkt_size(struct vnic_rx_bytes_counter *pkt_size,
                pkt_size->small_pkt_bytes_cnt += pkt_len;
 }
 
+static bool enic_rxcopybreak(struct net_device *netdev, struct sk_buff **skb,
+                            struct vnic_rq_buf *buf, u16 len)
+{
+       struct enic *enic = netdev_priv(netdev);
+       struct sk_buff *new_skb;
+
+       if (len > enic->rx_copybreak)
+               return false;
+       new_skb = netdev_alloc_skb_ip_align(netdev, len);
+       if (!new_skb)
+               return false;
+       pci_dma_sync_single_for_cpu(enic->pdev, buf->dma_addr, len,
+                                   DMA_FROM_DEVICE);
+       memcpy(new_skb->data, (*skb)->data, len);
+       *skb = new_skb;
+
+       return true;
+}
+
 static void enic_rq_indicate_buf(struct vnic_rq *rq,
        struct cq_desc *cq_desc, struct vnic_rq_buf *buf,
        int skipped, void *opaque)
@@ -978,9 +1017,6 @@ static void enic_rq_indicate_buf(struct vnic_rq *rq,
                return;
 
        skb = buf->os_buf;
-       prefetch(skb->data - NET_IP_ALIGN);
-       pci_unmap_single(enic->pdev, buf->dma_addr,
-               buf->len, PCI_DMA_FROMDEVICE);
 
        cq_enet_rq_desc_dec((struct cq_enet_rq_desc *)cq_desc,
                &type, &color, &q_number, &completed_index,
@@ -1011,6 +1047,13 @@ static void enic_rq_indicate_buf(struct vnic_rq *rq,
                /* Good receive
                 */
 
+               if (!enic_rxcopybreak(netdev, &skb, buf, bytes_written)) {
+                       buf->os_buf = NULL;
+                       pci_unmap_single(enic->pdev, buf->dma_addr, buf->len,
+                                        PCI_DMA_FROMDEVICE);
+               }
+               prefetch(skb->data - NET_IP_ALIGN);
+
                skb_put(skb, bytes_written);
                skb->protocol = eth_type_trans(skb, netdev);
                skb_record_rx_queue(skb, q_number);
@@ -2531,6 +2574,7 @@ static int enic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
                dev_err(dev, "Cannot register net device, aborting\n");
                goto err_out_dev_deinit;
        }
+       enic->rx_copybreak = RX_COPYBREAK_DEFAULT;
 
        return 0;