IPoIB/cm: Improve small message bandwidth

Avoid the overhead of freeing/reallocating and mapping/unmapping for
DMA pages that have not been written to by hardware.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
index 4d59682..3484e8b 100644 (file)
--- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
@@ -65,14 +65,14 @@ struct ipoib_cm_id {
 static int ipoib_cm_tx_handler(struct ib_cm_id *cm_id,
                               struct ib_cm_event *event);
 
-static void ipoib_cm_dma_unmap_rx(struct ipoib_dev_priv *priv,
+static void ipoib_cm_dma_unmap_rx(struct ipoib_dev_priv *priv, int frags,
                                  u64 mapping[IPOIB_CM_RX_SG])
 {
        int i;
 
        ib_dma_unmap_single(priv->ca, mapping[0], IPOIB_CM_HEAD_SIZE, DMA_FROM_DEVICE);
 
-       for (i = 0; i < IPOIB_CM_RX_SG - 1; ++i)
+       for (i = 0; i < frags; ++i)
                ib_dma_unmap_single(priv->ca, mapping[i + 1], PAGE_SIZE, DMA_FROM_DEVICE);
 }
 
@@ -90,7 +90,8 @@ static int ipoib_cm_post_receive(struct net_device *dev, int id)
        ret = ib_post_srq_recv(priv->cm.srq, &priv->cm.rx_wr, &bad_wr);
        if (unlikely(ret)) {
                ipoib_warn(priv, "post srq failed for buf %d (%d)\n", id, ret);
-               ipoib_cm_dma_unmap_rx(priv, priv->cm.srq_ring[id].mapping);
+               ipoib_cm_dma_unmap_rx(priv, IPOIB_CM_RX_SG - 1,
+                                     priv->cm.srq_ring[id].mapping);
                dev_kfree_skb_any(priv->cm.srq_ring[id].skb);
                priv->cm.srq_ring[id].skb = NULL;
        }
@@ -98,8 +99,8 @@ static int ipoib_cm_post_receive(struct net_device *dev, int id)
        return ret;
 }
 
-static int ipoib_cm_alloc_rx_skb(struct net_device *dev, int id,
-                                u64 mapping[IPOIB_CM_RX_SG])
+static struct sk_buff *ipoib_cm_alloc_rx_skb(struct net_device *dev, int id, int frags,
+                                            u64 mapping[IPOIB_CM_RX_SG])
 {
        struct ipoib_dev_priv *priv = netdev_priv(dev);
        struct sk_buff *skb;
@@ -107,7 +108,7 @@ static int ipoib_cm_alloc_rx_skb(struct net_device *dev, int id,
 
        skb = dev_alloc_skb(IPOIB_CM_HEAD_SIZE + 12);
        if (unlikely(!skb))
-               return -ENOMEM;
+               return NULL;
 
        /*
         * IPoIB adds a 4 byte header. So we need 12 more bytes to align the
@@ -119,10 +120,10 @@ static int ipoib_cm_alloc_rx_skb(struct net_device *dev, int id,
                                       DMA_FROM_DEVICE);
        if (unlikely(ib_dma_mapping_error(priv->ca, mapping[0]))) {
                dev_kfree_skb_any(skb);
-               return -EIO;
+               return NULL;
        }
 
-       for (i = 0; i < IPOIB_CM_RX_SG - 1; i++) {
+       for (i = 0; i < frags; i++) {
                struct page *page = alloc_page(GFP_ATOMIC);
 
                if (!page)
@@ -136,7 +137,7 @@ static int ipoib_cm_alloc_rx_skb(struct net_device *dev, int id,
        }
 
        priv->cm.srq_ring[id].skb = skb;
-       return 0;
+       return skb;
 
 partial_error:
 
@@ -146,7 +147,7 @@ partial_error:
                ib_dma_unmap_single(priv->ca, mapping[i + 1], PAGE_SIZE, DMA_FROM_DEVICE);
 
        dev_kfree_skb_any(skb);
-       return -ENOMEM;
+       return NULL;
 }
 
 static struct ib_qp *ipoib_cm_create_rx_qp(struct net_device *dev,
@@ -309,7 +310,7 @@ static int ipoib_cm_rx_handler(struct ib_cm_id *cm_id,
 }
 /* Adjust length of skb with fragments to match received data */
 static void skb_put_frags(struct sk_buff *skb, unsigned int hdr_space,
-                         unsigned int length)
+                         unsigned int length, struct sk_buff *toskb)
 {
        int i, num_frags;
        unsigned int size;
@@ -326,7 +327,7 @@ static void skb_put_frags(struct sk_buff *skb, unsigned int hdr_space,
 
                if (length == 0) {
                        /* don't need this page */
-                       __free_page(frag->page);
+                       skb_fill_page_desc(toskb, i, frag->page, 0, PAGE_SIZE);
                        --skb_shinfo(skb)->nr_frags;
                } else {
                        size = min(length, (unsigned) PAGE_SIZE);
@@ -344,10 +345,11 @@ void ipoib_cm_handle_rx_wc(struct net_device *dev, struct ib_wc *wc)
 {
        struct ipoib_dev_priv *priv = netdev_priv(dev);
        unsigned int wr_id = wc->wr_id & ~IPOIB_CM_OP_SRQ;
-       struct sk_buff *skb;
+       struct sk_buff *skb, *newskb;
        struct ipoib_cm_rx *p;
        unsigned long flags;
        u64 mapping[IPOIB_CM_RX_SG];
+       int frags;
 
        ipoib_dbg_data(priv, "cm recv completion: id %d, op %d, status: %d\n",
                       wr_id, wc->opcode, wc->status);
@@ -383,7 +385,11 @@ void ipoib_cm_handle_rx_wc(struct net_device *dev, struct ib_wc *wc)
                }
        }
 
-       if (unlikely(ipoib_cm_alloc_rx_skb(dev, wr_id, mapping))) {
+       frags = PAGE_ALIGN(wc->byte_len - min(wc->byte_len,
+                                             (unsigned)IPOIB_CM_HEAD_SIZE)) / PAGE_SIZE;
+
+       newskb = ipoib_cm_alloc_rx_skb(dev, wr_id, frags, mapping);
+       if (unlikely(!newskb)) {
                /*
                 * If we can't allocate a new RX buffer, dump
                 * this packet and reuse the old buffer.
@@ -393,13 +399,13 @@ void ipoib_cm_handle_rx_wc(struct net_device *dev, struct ib_wc *wc)
                goto repost;
        }
 
-       ipoib_cm_dma_unmap_rx(priv, priv->cm.srq_ring[wr_id].mapping);
-       memcpy(priv->cm.srq_ring[wr_id].mapping, mapping, sizeof mapping);
+       ipoib_cm_dma_unmap_rx(priv, frags, priv->cm.srq_ring[wr_id].mapping);
+       memcpy(priv->cm.srq_ring[wr_id].mapping, mapping, (frags + 1) * sizeof *mapping);
 
        ipoib_dbg_data(priv, "received %d bytes, SLID 0x%04x\n",
                       wc->byte_len, wc->slid);
 
-       skb_put_frags(skb, IPOIB_CM_HEAD_SIZE, wc->byte_len);
+       skb_put_frags(skb, IPOIB_CM_HEAD_SIZE, wc->byte_len, newskb);
 
        skb->protocol = ((struct ipoib_header *) skb->data)->proto;
        skb->mac.raw = skb->data;
@@ -1193,7 +1199,8 @@ int ipoib_cm_dev_init(struct net_device *dev)
        priv->cm.rx_wr.num_sge = IPOIB_CM_RX_SG;
 
        for (i = 0; i < ipoib_recvq_size; ++i) {
-               if (ipoib_cm_alloc_rx_skb(dev, i, priv->cm.srq_ring[i].mapping)) {
+               if (!ipoib_cm_alloc_rx_skb(dev, i, IPOIB_CM_RX_SG - 1,
+                                          priv->cm.srq_ring[i].mapping)) {
                        ipoib_warn(priv, "failed to allocate receive buffer %d\n", i);
                        ipoib_cm_dev_cleanup(dev);
                        return -ENOMEM;
@@ -1228,7 +1235,8 @@ void ipoib_cm_dev_cleanup(struct net_device *dev)
                return;
        for (i = 0; i < ipoib_recvq_size; ++i)
                if (priv->cm.srq_ring[i].skb) {
-                       ipoib_cm_dma_unmap_rx(priv, priv->cm.srq_ring[i].mapping);
+                       ipoib_cm_dma_unmap_rx(priv, IPOIB_CM_RX_SG - 1,
+                                             priv->cm.srq_ring[i].mapping);
                        dev_kfree_skb_any(priv->cm.srq_ring[i].skb);
                        priv->cm.srq_ring[i].skb = NULL;
                }