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Commit 9bc88939 authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
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tun: Add support for RFS on tun flows 



This patch adds support so that the rps_flow_tables (RFS) can be
programmed using the tun flows which are already set up to track flows
for the purposes of queue selection.

On the receive path (corresponding to select_queue and tun_net_xmit) the
rxhash is saved in the flow_entry.  The original code only does flow
lookup in select_queue, so this patch adds a flow lookup in tun_net_xmit
if num_queues == 1 (select_queue is not called from
dev_queue_xmit->netdev_pick_tx in that case).

The flow is recorded (processing CPU) in tun_flow_update (TX path), and
reset when flow is deleted.

Signed-off-by: default avatarTom Herbert <therbert@google.com>
Signed-off-by: default avatarZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fe477558

drivers/net/tun.c

+35 −2
Original line number Diff line number Diff line
@@ -152,6 +152,7 @@ struct tun_flow_entry { 
	struct tun_struct *tun;



	u32 rxhash;

	u32 rps_rxhash;

	int queue_index;

	unsigned long updated;

};
@@ -220,6 +221,7 @@ static struct tun_flow_entry *tun_flow_create(struct tun_struct *tun, 
			  rxhash, queue_index);

		e->updated = jiffies;

		e->rxhash = rxhash;

		e->rps_rxhash = 0;

		e->queue_index = queue_index;

		e->tun = tun;

		hlist_add_head_rcu(&e->hash_link, head);
@@ -232,6 +234,7 @@ static void tun_flow_delete(struct tun_struct *tun, struct tun_flow_entry *e) 
{

	tun_debug(KERN_INFO, tun, "delete flow: hash %u index %u\n",

		  e->rxhash, e->queue_index);

	sock_rps_reset_flow_hash(e->rps_rxhash);

	hlist_del_rcu(&e->hash_link);

	kfree_rcu(e, rcu);

	--tun->flow_count;
@@ -325,6 +328,7 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash, 
		/* TODO: keep queueing to old queue until it's empty? */

		e->queue_index = queue_index;

		e->updated = jiffies;

		sock_rps_record_flow_hash(e->rps_rxhash);

	} else {

		spin_lock_bh(&tun->lock);

		if (!tun_flow_find(head, rxhash) &&
@@ -341,6 +345,18 @@ static void tun_flow_update(struct tun_struct *tun, u32 rxhash, 
	rcu_read_unlock();

}



/**

 * Save the hash received in the stack receive path and update the

 * flow_hash table accordingly.

 */

static inline void tun_flow_save_rps_rxhash(struct tun_flow_entry *e, u32 hash)

{

	if (unlikely(e->rps_rxhash != hash)) {

		sock_rps_reset_flow_hash(e->rps_rxhash);

		e->rps_rxhash = hash;

	}

}



/* We try to identify a flow through its rxhash first. The reason that

 * we do not check rxq no. is because some cards(e.g 82599), chooses

 * the rxq based on the txq where the last packet of the flow comes. As
@@ -361,9 +377,10 @@ static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb) 
	txq = skb_get_hash(skb);

	if (txq) {

		e = tun_flow_find(&tun->flows[tun_hashfn(txq)], txq);

		if (e)

		if (e) {

			txq = e->queue_index;

		else

			tun_flow_save_rps_rxhash(e, txq);

		} else

			/* use multiply and shift instead of expensive divide */

			txq = ((u64)txq * numqueues) >> 32;

	} else if (likely(skb_rx_queue_recorded(skb))) {
@@ -728,6 +745,22 @@ static netdev_tx_t tun_net_xmit(struct sk_buff *skb, struct net_device *dev) 
	if (txq >= tun->numqueues)

		goto drop;



	if (tun->numqueues == 1) {

		/* Select queue was not called for the skbuff, so we extract the

		 * RPS hash and save it into the flow_table here.

		 */

		__u32 rxhash;



		rxhash = skb_get_hash(skb);

		if (rxhash) {

			struct tun_flow_entry *e;

			e = tun_flow_find(&tun->flows[tun_hashfn(rxhash)],

					rxhash);

			if (e)

				tun_flow_save_rps_rxhash(e, rxhash);

		}

	}



	tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len);



	BUG_ON(!tfile);