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Date: Thu, 14 Aug 2014 14:59:18 +0530
From: Govindarajulu Varadarajan <_govind@....com>
To: davem@...emloft.net, netdev@...r.kernel.org
Cc: ben@...adent.org.uk, stephen@...workplumber.org, ssujith@...co.com,
benve@...co.com, Govindarajulu Varadarajan <_govind@....com>
Subject: [PATCH net-next v3 1/3] 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@....com>
---
drivers/net/ethernet/cisco/enic/enic.h | 1 +
drivers/net/ethernet/cisco/enic/enic_main.c | 50 +++++++++++++++++++++++++++--
2 files changed, 48 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ethernet/cisco/enic/enic.h b/drivers/net/ethernet/cisco/enic/enic.h
index 962510f..5ba5ad0 100644
--- 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 9348feb..b7e69fd 100644
--- 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 DEFINE_PCI_DEVICE_TABLE(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;
--
2.0.4
--
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