[PATCH RFC 8/9] veth: Avoid per-packet spinlock of XDP napi ring on dequeueing

[Toshiaki Makita]

From: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>

Use percpu temporary storage to avoid per-packet spinlock.

Signed-off-by: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>
---
 drivers/net/veth.c | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 98fc91a64e29..1592119e3873 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -30,6 +30,7 @@
 #define VETH_XDP_FLAG          0x1UL
 #define VETH_RING_SIZE         256
 #define VETH_XDP_HEADROOM      (XDP_PACKET_HEADROOM + NET_IP_ALIGN)
+#define VETH_XDP_QUEUE_SIZE    NAPI_POLL_WEIGHT
 
 struct pcpu_vstats {
        u64                     packets;
@@ -50,6 +51,8 @@ struct veth_priv {
        struct xdp_rxq_info     xdp_rxq;
 };
 
+static DEFINE_PER_CPU(void *[VETH_XDP_QUEUE_SIZE], xdp_consume_q);
+
 static bool veth_is_xdp_frame(void *ptr)
 {
        return (unsigned long)ptr & VETH_XDP_FLAG;
@@ -563,27 +566,32 @@ static struct sk_buff *veth_xdp_rcv_skb(struct veth_priv 
*priv,
 static int veth_xdp_rcv(struct veth_priv *priv, int budget, bool *xdp_xmit,
                        bool *xdp_redir)
 {
-       int i, done = 0;
-
-       for (i = 0; i < budget; i++) {
-               void *ptr = ptr_ring_consume(&priv->xdp_ring);
-               struct sk_buff *skb;
-
-               if (!ptr)
-                       break;
+       void **q = this_cpu_ptr(xdp_consume_q);
+       int num, lim, done = 0;
+
+       do {
+               int i;
+
+               lim = min(budget - done, VETH_XDP_QUEUE_SIZE);
+               num = ptr_ring_consume_batched(&priv->xdp_ring, q, lim);
+               for (i = 0; i < num; i++) {
+                       struct sk_buff *skb;
+                       void *ptr = q[i];
+
+                       if (veth_is_xdp_frame(ptr)) {
+                               skb = veth_xdp_rcv_one(priv,
+                                                      veth_ptr_to_xdp(ptr),
+                                                      xdp_xmit, xdp_redir);
+                       } else {
+                               skb = veth_xdp_rcv_skb(priv, ptr, xdp_xmit,
+                                                      xdp_redir);
+                       }
 
-               if (veth_is_xdp_frame(ptr)) {
-                       skb = veth_xdp_rcv_one(priv, veth_ptr_to_xdp(ptr),
-                                              xdp_xmit, xdp_redir);
-               } else {
-                       skb = veth_xdp_rcv_skb(priv, ptr, xdp_xmit, xdp_redir);
+                       if (skb)
+                               napi_gro_receive(&priv->xdp_napi, skb);
                }
-
-               if (skb)
-                       napi_gro_receive(&priv->xdp_napi, skb);
-
-               done++;
-       }
+               done += num;
+       } while (unlikely(num == lim && done < budget));
 
        return done;
 }
-- 
2.14.3