xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Garpu 0
Kode Masalah Tarik Permintaan Actions Packages Projects Rilis Wiki Kegiatan

net: better IFF_XMIT_DST_RELEASE support

Telusuri Sumber 
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>
This commit is contained in:
Eric Dumazet
2014-10-05 18:38:35 -07:00
committed by David S. Miller
orang tua fe971b95c2
melakukan 0287587884
27 mengubah file dengan 54 tambahan dan 39 penghapusan
Download Patch File Download Diff File Expand all files Collapse all files

19
net/core/dev.c
Melihat File

@@ -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;