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xps: Improvements in TX queue selection 

In dev_pick_tx, don't do work in calculating queue
index or setting
the index in the sock unless the device has more than one queue.  This
allows the sock to be set only with a queue index of a multi-queue
device which is desirable if device are stacked like in a tunnel.

We also allow the mapping of a socket to queue to be changed.  To
maintain in order packet transmission a flag (ooo_okay) has been
added to the sk_buff structure.  If a transport layer sets this flag
on a packet, the transmit queue can be changed for the socket.
Presumably, the transport would set this if there was no possbility
of creating OOO packets (for instance, there are no packets in flight
for the socket).  This patch includes the modification in TCP output
for setting this flag.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert 2010-11-21 13:17:29 +00:00 committed by David S. Miller
parent 22f4fbd9bd
commit 3853b5841c
3 changed files with 17 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/skbuff.h
View File

@ -386,9 +386,10 @@ struct sk_buff {
#else
__u8 deliver_no_wcard:1;
#endif
__u8 ooo_okay:1;
kmemcheck_bitfield_end(flags2);
/* 0/14 bit hole */
/* 0/13 bit hole */
#ifdef CONFIG_NET_DMA
dma_cookie_t dma_cookie;

18
net/core/dev.c
View File

@ -2148,20 +2148,24 @@ static struct netdev_queue *dev_pick_tx(struct net_device *dev,
int queue_index;
const struct net_device_ops *ops = dev->netdev_ops;
if (ops->ndo_select_queue) {
if (dev->real_num_tx_queues == 1)
queue_index = 0;
else if (ops->ndo_select_queue) {
queue_index = ops->ndo_select_queue(dev, skb);
queue_index = dev_cap_txqueue(dev, queue_index);
} else {
struct sock *sk = skb->sk;
queue_index = sk_tx_queue_get(sk);
if (queue_index < 0 || queue_index >= dev->real_num_tx_queues) {
queue_index = 0;
if (dev->real_num_tx_queues > 1)
queue_index = skb_tx_hash(dev, skb);
if (queue_index < 0 || skb->ooo_okay ||
queue_index >= dev->real_num_tx_queues) {
int old_index = queue_index;
if (sk) {
struct dst_entry *dst = rcu_dereference_check(sk->sk_dst_cache, 1);
queue_index = skb_tx_hash(dev, skb);
if (queue_index != old_index && sk) {
struct dst_entry *dst =
rcu_dereference_check(sk->sk_dst_cache, 1);
if (dst && skb_dst(skb) == dst)
sk_tx_queue_set(sk, queue_index);

5
net/ipv4/tcp_output.c
View File

@ -822,8 +822,11 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
&md5);
tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
if (tcp_packets_in_flight(tp) == 0)
if (tcp_packets_in_flight(tp) == 0) {
tcp_ca_event(sk, CA_EVENT_TX_START);
skb->ooo_okay = 1;
} else
skb->ooo_okay = 0;
skb_push(skb, tcp_header_size);
skb_reset_transport_header(skb);