xdp: change ndo_xdp_xmit API to support bulking

This patch change the API for ndo_xdp_xmit to support bulking
xdp_frames.

When kernel is compiled with CONFIG_RETPOLINE, XDP sees a huge slowdown.
Most of the slowdown is caused by DMA API indirect function calls, but
also the net_device->ndo_xdp_xmit() call.

Benchmarked patch with CONFIG_RETPOLINE, using xdp_redirect_map with
single flow/core test (CPU E5-1650 v4 @ 3.60GHz), showed
performance improved:
 for driver ixgbe: 6,042,682 pps -> 6,853,768 pps = +811,086 pps
 for driver i40e : 6,187,169 pps -> 6,724,519 pps = +537,350 pps

With frames avail as a bulk inside the driver ndo_xdp_xmit call,
further optimizations are possible, like bulk DMA-mapping for TX.

Testing without CONFIG_RETPOLINE show the same performance for
physical NIC drivers.

The virtual NIC driver tun sees a huge performance boost, as it can
avoid doing per frame producer locking, but instead amortize the
locking cost over the bulk.

V2: Fix compile errors reported by kbuild test robot <lkp@intel.com>
V4: Isolated ndo, driver changes and callers.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.c b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
index 5efa68d..9b698c5 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.c
@@ -3664,14 +3664,19 @@ netdev_tx_t i40e_lan_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
  * @dev: netdev
  * @xdp: XDP buffer
  *
- * Returns Zero if sent, else an error code
+ * Returns number of frames successfully sent. Frames that fail are
+ * free'ed via XDP return API.
+ *
+ * For error cases, a negative errno code is returned and no-frames
+ * are transmitted (caller must handle freeing frames).
  **/
-int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+int i40e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames)
 {
        struct i40e_netdev_priv *np = netdev_priv(dev);
        unsigned int queue_index = smp_processor_id();
        struct i40e_vsi *vsi = np->vsi;
-       int err;
+       int drops = 0;
+       int i;
 
        if (test_bit(__I40E_VSI_DOWN, vsi->state))
                return -ENETDOWN;
@@ -3679,11 +3684,18 @@ int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
        if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs)
                return -ENXIO;
 
-       err = i40e_xmit_xdp_ring(xdpf, vsi->xdp_rings[queue_index]);
-       if (err != I40E_XDP_TX)
-               return -ENOSPC;
+       for (i = 0; i < n; i++) {
+               struct xdp_frame *xdpf = frames[i];
+               int err;
 
-       return 0;
+               err = i40e_xmit_xdp_ring(xdpf, vsi->xdp_rings[queue_index]);
+               if (err != I40E_XDP_TX) {
+                       xdp_return_frame_rx_napi(xdpf);
+                       drops++;
+               }
+       }
+
+       return n - drops;
 }
 
 /**

diff --git a/drivers/net/ethernet/intel/i40e/i40e_txrx.h b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
index fdd2c55..eb8804b 100644 (file)
--- a/drivers/net/ethernet/intel/i40e/i40e_txrx.h
+++ b/drivers/net/ethernet/intel/i40e/i40e_txrx.h
@@ -487,7 +487,7 @@ u32 i40e_get_tx_pending(struct i40e_ring *ring, bool in_sw);
 void i40e_detect_recover_hung(struct i40e_vsi *vsi);
 int __i40e_maybe_stop_tx(struct i40e_ring *tx_ring, int size);
 bool __i40e_chk_linearize(struct sk_buff *skb);
-int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf);
+int i40e_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames);
 void i40e_xdp_flush(struct net_device *dev);
 
 /**

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
index 6652b20..9645619 100644 (file)
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_main.c
@@ -10017,11 +10017,13 @@ static int ixgbe_xdp(struct net_device *dev, struct netdev_bpf *xdp)
        }
 }
 
-static int ixgbe_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+static int ixgbe_xdp_xmit(struct net_device *dev, int n,
+                         struct xdp_frame **frames)
 {
        struct ixgbe_adapter *adapter = netdev_priv(dev);
        struct ixgbe_ring *ring;
-       int err;
+       int drops = 0;
+       int i;
 
        if (unlikely(test_bit(__IXGBE_DOWN, &adapter->state)))
                return -ENETDOWN;
@@ -10033,11 +10035,18 @@ static int ixgbe_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
        if (unlikely(!ring))
                return -ENXIO;
 
-       err = ixgbe_xmit_xdp_ring(adapter, xdpf);
-       if (err != IXGBE_XDP_TX)
-               return -ENOSPC;
+       for (i = 0; i < n; i++) {
+               struct xdp_frame *xdpf = frames[i];
+               int err;
 
-       return 0;
+               err = ixgbe_xmit_xdp_ring(adapter, xdpf);
+               if (err != IXGBE_XDP_TX) {
+                       xdp_return_frame_rx_napi(xdpf);
+                       drops++;
+               }
+       }
+
+       return n - drops;
 }
 
 static void ixgbe_xdp_flush(struct net_device *dev)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 44d4f3d..d3dcfcb 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -70,6 +70,7 @@
 #include <net/netns/generic.h>
 #include <net/rtnetlink.h>
 #include <net/sock.h>
+#include <net/xdp.h>
 #include <linux/seq_file.h>
 #include <linux/uio.h>
 #include <linux/skb_array.h>
@@ -1290,34 +1291,44 @@ static const struct net_device_ops tun_netdev_ops = {
        .ndo_get_stats64        = tun_net_get_stats64,
 };
 
-static int tun_xdp_xmit(struct net_device *dev, struct xdp_frame *frame)
+static int tun_xdp_xmit(struct net_device *dev, int n, struct xdp_frame **frames)
 {
        struct tun_struct *tun = netdev_priv(dev);
        struct tun_file *tfile;
        u32 numqueues;
-       int ret = 0;
+       int drops = 0;
+       int cnt = n;
+       int i;
 
        rcu_read_lock();
 
        numqueues = READ_ONCE(tun->numqueues);
        if (!numqueues) {
-               ret = -ENOSPC;
-               goto out;
+               rcu_read_unlock();
+               return -ENXIO; /* Caller will free/return all frames */
        }
 
        tfile = rcu_dereference(tun->tfiles[smp_processor_id() %
                                            numqueues]);
-       /* Encode the XDP flag into lowest bit for consumer to differ
-        * XDP buffer from sk_buff.
-        */
-       if (ptr_ring_produce(&tfile->tx_ring, tun_xdp_to_ptr(frame))) {
-               this_cpu_inc(tun->pcpu_stats->tx_dropped);
-               ret = -ENOSPC;
+
+       spin_lock(&tfile->tx_ring.producer_lock);
+       for (i = 0; i < n; i++) {
+               struct xdp_frame *xdp = frames[i];
+               /* Encode the XDP flag into lowest bit for consumer to differ
+                * XDP buffer from sk_buff.
+                */
+               void *frame = tun_xdp_to_ptr(xdp);
+
+               if (__ptr_ring_produce(&tfile->tx_ring, frame)) {
+                       this_cpu_inc(tun->pcpu_stats->tx_dropped);
+                       xdp_return_frame_rx_napi(xdp);
+                       drops++;
+               }
        }
+       spin_unlock(&tfile->tx_ring.producer_lock);
 
-out:
        rcu_read_unlock();
-       return ret;
+       return cnt - drops;
 }
 
 static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
@@ -1327,7 +1338,7 @@ static int tun_xdp_tx(struct net_device *dev, struct xdp_buff *xdp)
        if (unlikely(!frame))
                return -EOVERFLOW;
 
-       return tun_xdp_xmit(dev, frame);
+       return tun_xdp_xmit(dev, 1, &frame);
 }
 
 static void tun_xdp_flush(struct net_device *dev)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index f34794a..39a0783 100644 (file)
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -419,23 +419,13 @@ static void virtnet_xdp_flush(struct net_device *dev)
        virtqueue_kick(sq->vq);
 }
 
-static int __virtnet_xdp_xmit(struct virtnet_info *vi,
-                              struct xdp_frame *xdpf)
+static int __virtnet_xdp_xmit_one(struct virtnet_info *vi,
+                                  struct send_queue *sq,
+                                  struct xdp_frame *xdpf)
 {
        struct virtio_net_hdr_mrg_rxbuf *hdr;
-       struct xdp_frame *xdpf_sent;
-       struct send_queue *sq;
-       unsigned int len;
-       unsigned int qp;
        int err;
 
-       qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
-       sq = &vi->sq[qp];
-
-       /* Free up any pending old buffers before queueing new ones. */
-       while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
-               xdp_return_frame(xdpf_sent);
-
        /* virtqueue want to use data area in-front of packet */
        if (unlikely(xdpf->metasize > 0))
                return -EOPNOTSUPP;
@@ -459,11 +449,40 @@ static int __virtnet_xdp_xmit(struct virtnet_info *vi,
        return 0;
 }
 
-static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
+static int __virtnet_xdp_tx_xmit(struct virtnet_info *vi,
+                                  struct xdp_frame *xdpf)
+{
+       struct xdp_frame *xdpf_sent;
+       struct send_queue *sq;
+       unsigned int len;
+       unsigned int qp;
+
+       qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+       sq = &vi->sq[qp];
+
+       /* Free up any pending old buffers before queueing new ones. */
+       while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
+               xdp_return_frame(xdpf_sent);
+
+       return __virtnet_xdp_xmit_one(vi, sq, xdpf);
+}
+
+static int virtnet_xdp_xmit(struct net_device *dev,
+                           int n, struct xdp_frame **frames)
 {
        struct virtnet_info *vi = netdev_priv(dev);
        struct receive_queue *rq = vi->rq;
+       struct xdp_frame *xdpf_sent;
        struct bpf_prog *xdp_prog;
+       struct send_queue *sq;
+       unsigned int len;
+       unsigned int qp;
+       int drops = 0;
+       int err;
+       int i;
+
+       qp = vi->curr_queue_pairs - vi->xdp_queue_pairs + smp_processor_id();
+       sq = &vi->sq[qp];
 
        /* Only allow ndo_xdp_xmit if XDP is loaded on dev, as this
         * indicate XDP resources have been successfully allocated.
@@ -472,7 +491,20 @@ static int virtnet_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
        if (!xdp_prog)
                return -ENXIO;
 
-       return __virtnet_xdp_xmit(vi, xdpf);
+       /* Free up any pending old buffers before queueing new ones. */
+       while ((xdpf_sent = virtqueue_get_buf(sq->vq, &len)) != NULL)
+               xdp_return_frame(xdpf_sent);
+
+       for (i = 0; i < n; i++) {
+               struct xdp_frame *xdpf = frames[i];
+
+               err = __virtnet_xdp_xmit_one(vi, sq, xdpf);
+               if (err) {
+                       xdp_return_frame_rx_napi(xdpf);
+                       drops++;
+               }
+       }
+       return n - drops;
 }
 
 static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
@@ -616,7 +648,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
                        xdpf = convert_to_xdp_frame(&xdp);
                        if (unlikely(!xdpf))
                                goto err_xdp;
-                       err = __virtnet_xdp_xmit(vi, xdpf);
+                       err = __virtnet_xdp_tx_xmit(vi, xdpf);
                        if (unlikely(err)) {
                                trace_xdp_exception(vi->dev, xdp_prog, act);
                                goto err_xdp;
@@ -779,7 +811,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
                        xdpf = convert_to_xdp_frame(&xdp);
                        if (unlikely(!xdpf))
                                goto err_xdp;
-                       err = __virtnet_xdp_xmit(vi, xdpf);
+                       err = __virtnet_xdp_tx_xmit(vi, xdpf);
                        if (unlikely(err)) {
                                trace_xdp_exception(vi->dev, xdp_prog, act);
                                if (unlikely(xdp_page != page))

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 03ed492..debdb62 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1185,9 +1185,13 @@ struct dev_ifalias {
  *     This function is used to set or query state related to XDP on the
  *     netdevice and manage BPF offload. See definition of
  *     enum bpf_netdev_command for details.
- * int (*ndo_xdp_xmit)(struct net_device *dev, struct xdp_frame *xdp);
- *     This function is used to submit a XDP packet for transmit on a
- *     netdevice.
+ * int (*ndo_xdp_xmit)(struct net_device *dev, int n, struct xdp_frame **xdp);
+ *     This function is used to submit @n XDP packets for transmit on a
+ *     netdevice. Returns number of frames successfully transmitted, frames
+ *     that got dropped are freed/returned via xdp_return_frame().
+ *     Returns negative number, means general error invoking ndo, meaning
+ *     no frames were xmit'ed and core-caller will free all frames.
+ *     TODO: Consider add flag to allow sending flush operation.
  * void (*ndo_xdp_flush)(struct net_device *dev);
  *     This function is used to inform the driver to flush a particular
  *     xdp tx queue. Must be called on same CPU as xdp_xmit.
@@ -1375,8 +1379,8 @@ struct net_device_ops {
                                                       int needed_headroom);
        int                     (*ndo_bpf)(struct net_device *dev,
                                           struct netdev_bpf *bpf);
-       int                     (*ndo_xdp_xmit)(struct net_device *dev,
-                                               struct xdp_frame *xdp);
+       int                     (*ndo_xdp_xmit)(struct net_device *dev, int n,
+                                               struct xdp_frame **xdp);
        void                    (*ndo_xdp_flush)(struct net_device *dev);
 };
 

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a9cd5c9..7790831 100644 (file)
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -232,24 +232,31 @@ static int bq_xmit_all(struct bpf_dtab_netdev *obj,
                prefetch(xdpf);
        }
 
-       for (i = 0; i < bq->count; i++) {
-               struct xdp_frame *xdpf = bq->q[i];
-               int err;
-
-               err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
-               if (err) {
-                       drops++;
-                       xdp_return_frame_rx_napi(xdpf);
-               } else {
-                       sent++;
-               }
+       sent = dev->netdev_ops->ndo_xdp_xmit(dev, bq->count, bq->q);
+       if (sent < 0) {
+               sent = 0;
+               goto error;
        }
+       drops = bq->count - sent;
+out:
        bq->count = 0;
 
        trace_xdp_devmap_xmit(&obj->dtab->map, obj->bit,
                              sent, drops, bq->dev_rx, dev);
        bq->dev_rx = NULL;
        return 0;
+error:
+       /* If ndo_xdp_xmit fails with an errno, no frames have been
+        * xmit'ed and it's our responsibility to them free all.
+        */
+       for (i = 0; i < bq->count; i++) {
+               struct xdp_frame *xdpf = bq->q[i];
+
+               /* RX path under NAPI protection, can return frames faster */
+               xdp_return_frame_rx_napi(xdpf);
+               drops++;
+       }
+       goto out;
 }
 
 /* __dev_map_flush is called from xdp_do_flush_map() which _must_ be signaled

diff --git a/net/core/filter.c b/net/core/filter.c
index 36cf2f8..1d75f93 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3039,7 +3039,7 @@ static int __bpf_tx_xdp(struct net_device *dev,
                        u32 index)
 {
        struct xdp_frame *xdpf;
-       int err;
+       int sent;
 
        if (!dev->netdev_ops->ndo_xdp_xmit) {
                return -EOPNOTSUPP;
@@ -3049,9 +3049,9 @@ static int __bpf_tx_xdp(struct net_device *dev,
        if (unlikely(!xdpf))
                return -EOVERFLOW;
 
-       err = dev->netdev_ops->ndo_xdp_xmit(dev, xdpf);
-       if (err)
-               return err;
+       sent = dev->netdev_ops->ndo_xdp_xmit(dev, 1, &xdpf);
+       if (sent <= 0)
+               return sent;
        dev->netdev_ops->ndo_xdp_flush(dev);
        return 0;
 }