hv_netvsc: use skb_get_hash() instead of a homegrown implementation

Recent changes to 'struct flow_keys' (e.g commit d34af823ff40 ("net: Add
VLAN ID to flow_keys")) introduced a performance regression in netvsc
driver. Is problem is, however, not the above mentioned commit but the
fact that netvsc_set_hash() function did some assumptions on the struct
flow_keys data layout and this is wrong.

Get rid of netvsc_set_hash() by switching to skb_get_hash(). This change
will also imply switching to Jenkins hash from the currently used Toeplitz
but it seems there is no good excuse for Toeplitz to stay.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 1c8db9a..1d3a665 100644 (file)
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -196,65 +196,6 @@ static void *init_ppi_data(struct rndis_message *msg, u32 ppi_size,
        return ppi;
 }
 
-union sub_key {
-       u64 k;
-       struct {
-               u8 pad[3];
-               u8 kb;
-               u32 ka;
-       };
-};
-
-/* Toeplitz hash function
- * data: network byte order
- * return: host byte order
- */
-static u32 comp_hash(u8 *key, int klen, void *data, int dlen)
-{
-       union sub_key subk;
-       int k_next = 4;
-       u8 dt;
-       int i, j;
-       u32 ret = 0;
-
-       subk.k = 0;
-       subk.ka = ntohl(*(u32 *)key);
-
-       for (i = 0; i < dlen; i++) {
-               subk.kb = key[k_next];
-               k_next = (k_next + 1) % klen;
-               dt = ((u8 *)data)[i];
-               for (j = 0; j < 8; j++) {
-                       if (dt & 0x80)
-                               ret ^= subk.ka;
-                       dt <<= 1;
-                       subk.k <<= 1;
-               }
-       }
-
-       return ret;
-}
-
-static bool netvsc_set_hash(u32 *hash, struct sk_buff *skb)
-{
-       struct flow_keys flow;
-       int data_len;
-
-       if (!skb_flow_dissect_flow_keys(skb, &flow, 0) ||
-           !(flow.basic.n_proto == htons(ETH_P_IP) ||
-             flow.basic.n_proto == htons(ETH_P_IPV6)))
-               return false;
-
-       if (flow.basic.ip_proto == IPPROTO_TCP)
-               data_len = 12;
-       else
-               data_len = 8;
-
-       *hash = comp_hash(netvsc_hash_key, HASH_KEYLEN, &flow, data_len);
-
-       return true;
-}
-
 static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
                        void *accel_priv, select_queue_fallback_t fallback)
 {
@@ -267,11 +208,9 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
        if (nvsc_dev == NULL || ndev->real_num_tx_queues <= 1)
                return 0;
 
-       if (netvsc_set_hash(&hash, skb)) {
-               q_idx = nvsc_dev->send_table[hash % VRSS_SEND_TAB_SIZE] %
-                       ndev->real_num_tx_queues;
-               skb_set_hash(skb, hash, PKT_HASH_TYPE_L3);
-       }
+       hash = skb_get_hash(skb);
+       q_idx = nvsc_dev->send_table[hash % VRSS_SEND_TAB_SIZE] %
+               ndev->real_num_tx_queues;
 
        if (!nvsc_dev->chn_table[q_idx])
                q_idx = 0;