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tun: Add support for RFS on tun flows

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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: Tom Herbert <therbert@google.com>
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert 2013-12-22 18:54:32 +08:00 committed by David S. Miller
parent fe47755852
commit 9bc8893937
1 changed files with 35 additions and 2 deletions
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37
drivers/net/tun.c
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@ -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 @@ unlock:
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);