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author | Eric Dumazet <edumazet@google.com> | 2014-10-05 18:38:35 -0700 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-10-07 13:22:11 -0400 |
commit | 0287587884b15041203b3a362d485e1ab1f24445 (patch) | |
tree | 675ae57663c1ba3ee8768e65e7fb0e6d0259e04c /net/core | |
parent | fe971b95c22578456ff7198537827841c726d3f7 (diff) | |
download | linux-0287587884b15041203b3a362d485e1ab1f24445.tar.gz linux-0287587884b15041203b3a362d485e1ab1f24445.tar.bz2 linux-0287587884b15041203b3a362d485e1ab1f24445.zip |
net: better IFF_XMIT_DST_RELEASE support
Testing xmit_more support with netperf and connected UDP sockets,
I found strange dst refcount false sharing.
Current handling of IFF_XMIT_DST_RELEASE is not optimal.
Dropping dst in validate_xmit_skb() is certainly too late in case
packet was queued by cpu X but dequeued by cpu Y
The logical point to take care of drop/force is in __dev_queue_xmit()
before even taking qdisc lock.
As Julian Anastasov pointed out, need for skb_dst() might come from some
packet schedulers or classifiers.
This patch adds new helper to cleanly express needs of various drivers
or qdiscs/classifiers.
Drivers that need skb_dst() in their ndo_start_xmit() should call
following helper in their setup instead of the prior :
dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
->
netif_keep_dst(dev);
Instead of using a single bit, we use two bits, one being
eventually rebuilt in bonding/team drivers.
The other one, is permanent and blocks IFF_XMIT_DST_RELEASE being
rebuilt in bonding/team. Eventually, we could add something
smarter later.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r-- | net/core/dev.c | 19 |
1 files changed, 9 insertions, 10 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index a63b8c43c1b6..3c5bdaa44486 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2665,12 +2665,6 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device if (skb->next) return skb; - /* If device doesn't need skb->dst, release it right now while - * its hot in this cpu cache - */ - if (dev->priv_flags & IFF_XMIT_DST_RELEASE) - skb_dst_drop(skb); - features = netif_skb_features(skb); skb = validate_xmit_vlan(skb, features); if (unlikely(!skb)) @@ -2811,8 +2805,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, * waiting to be sent out; and the qdisc is not running - * xmit the skb directly. */ - if (!(dev->priv_flags & IFF_XMIT_DST_RELEASE)) - skb_dst_force(skb); qdisc_bstats_update(q, skb); @@ -2827,7 +2819,6 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q, rc = NET_XMIT_SUCCESS; } else { - skb_dst_force(skb); rc = q->enqueue(skb, q) & NET_XMIT_MASK; if (qdisc_run_begin(q)) { if (unlikely(contended)) { @@ -2924,6 +2915,14 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv) skb_update_prio(skb); + /* If device/qdisc don't need skb->dst, release it right now while + * its hot in this cpu cache. + */ + if (dev->priv_flags & IFF_XMIT_DST_RELEASE) + skb_dst_drop(skb); + else + skb_dst_force(skb); + txq = netdev_pick_tx(dev, skb, accel_priv); q = rcu_dereference_bh(txq->qdisc); @@ -6674,7 +6673,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name, INIT_LIST_HEAD(&dev->adj_list.lower); INIT_LIST_HEAD(&dev->all_adj_list.upper); INIT_LIST_HEAD(&dev->all_adj_list.lower); - dev->priv_flags = IFF_XMIT_DST_RELEASE; + dev->priv_flags = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM; setup(dev); dev->num_tx_queues = txqs; |