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Commit 757647e1 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by David S. Miller
Browse files

hv_netvsc: use skb_get_hash() instead of a homegrown implementation 



Recent changes to 'struct flow_keys' (e.g commit d34af823 ("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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 87e57399

drivers/net/hyperv/netvsc_drv.c

+3 −64
Original line number Diff line number Diff line
@@ -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)) {

	hash = skb_get_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);

	}



	if (!nvsc_dev->chn_table[q_idx])

		q_idx = 0;