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authorJohn Fastabend <john.fastabend@gmail.com>2017-12-07 09:54:25 -0800
committerDavid S. Miller <davem@davemloft.net>2017-12-08 13:32:25 -0500
commit6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7 (patch)
tree9acd6f0cac4ac67578c21c74d29a3684c15dbe32 /net/sched/sch_generic.c
parent6c148184b5c868ad2c8a5a4a777cd8097622368a (diff)
downloadlinux-sh-6b3ba9146fe64b9bebb6346c9dcfe3b4851de2d7.tar.gz
net: sched: allow qdiscs to handle locking
This patch adds a flag for queueing disciplines to indicate the stack does not need to use the qdisc lock to protect operations. This can be used to build lockless scheduling algorithms and improving performance. The flag is checked in the tx path and the qdisc lock is only taken if it is not set. For now use a conditional if statement. Later we could be more aggressive if it proves worthwhile and use a static key or wrap this in a likely(). Also the lockless case drops the TCQ_F_CAN_BYPASS logic. The reason for this is synchronizing a qlen counter across threads proves to cost more than doing the enqueue/dequeue operations when tested with pktgen. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_generic.c')
-rw-r--r--net/sched/sch_generic.c30
1 files changed, 20 insertions, 10 deletions
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index f6803e1d6783..ec757f66896a 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -174,7 +174,8 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
int ret = NETDEV_TX_BUSY;
/* And release qdisc */
- spin_unlock(root_lock);
+ if (root_lock)
+ spin_unlock(root_lock);
/* Note that we validate skb (GSO, checksum, ...) outside of locks */
if (validate)
@@ -187,10 +188,13 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
HARD_TX_UNLOCK(dev, txq);
} else {
- spin_lock(root_lock);
+ if (root_lock)
+ spin_lock(root_lock);
return qdisc_qlen(q);
}
- spin_lock(root_lock);
+
+ if (root_lock)
+ spin_lock(root_lock);
if (dev_xmit_complete(ret)) {
/* Driver sent out skb successfully or skb was consumed */
@@ -231,9 +235,9 @@ int sch_direct_xmit(struct sk_buff *skb, struct Qdisc *q,
*/
static inline int qdisc_restart(struct Qdisc *q, int *packets)
{
+ spinlock_t *root_lock = NULL;
struct netdev_queue *txq;
struct net_device *dev;
- spinlock_t *root_lock;
struct sk_buff *skb;
bool validate;
@@ -242,7 +246,9 @@ static inline int qdisc_restart(struct Qdisc *q, int *packets)
if (unlikely(!skb))
return 0;
- root_lock = qdisc_lock(q);
+ if (!(q->flags & TCQ_F_NOLOCK))
+ root_lock = qdisc_lock(q);
+
dev = qdisc_dev(q);
txq = skb_get_tx_queue(dev, skb);
@@ -880,14 +886,18 @@ static bool some_qdisc_is_busy(struct net_device *dev)
dev_queue = netdev_get_tx_queue(dev, i);
q = dev_queue->qdisc_sleeping;
- root_lock = qdisc_lock(q);
- spin_lock_bh(root_lock);
+ if (q->flags & TCQ_F_NOLOCK) {
+ val = test_bit(__QDISC_STATE_SCHED, &q->state);
+ } else {
+ root_lock = qdisc_lock(q);
+ spin_lock_bh(root_lock);
- val = (qdisc_is_running(q) ||
- test_bit(__QDISC_STATE_SCHED, &q->state));
+ val = (qdisc_is_running(q) ||
+ test_bit(__QDISC_STATE_SCHED, &q->state));
- spin_unlock_bh(root_lock);
+ spin_unlock_bh(root_lock);
+ }
if (val)
return true;