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net: introduce dev_consume_skb_any() 

Some network drivers use dev_kfree_skb_any() and dev_kfree_skb_irq()
helpers to free skbs, both for dropped packets and TX completed ones.

We need to separate the two causes to get better diagnostics
given by dropwatch or "perf record -e skb:kfree_skb"

This patch provides two new helpers, dev_consume_skb_any() and
dev_consume_skb_irq() to be used for consumed skbs.

__dev_kfree_skb_irq() is slightly optimized to remove one
atomic_dec_and_test() in fast path, and use this_cpu_{r|w} accessors.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-12-05 04:45:08 -08:00 committed by David S. Miller
parent f96eb74c84
commit e6247027e5
2 changed files with 76 additions and 26 deletions
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53
include/linux/netdevice.h
View File

@ -2368,17 +2368,52 @@ static inline int netif_copy_real_num_queues(struct net_device *to_dev,
#define DEFAULT_MAX_NUM_RSS_QUEUES (8)
int netif_get_num_default_rss_queues(void);
/* Use this variant when it is known for sure that it
* is executing from hardware interrupt context or with hardware interrupts
* disabled.
*/
void dev_kfree_skb_irq(struct sk_buff *skb);
enum skb_free_reason {
SKB_REASON_CONSUMED,
SKB_REASON_DROPPED,
};
/* Use this variant in places where it could be invoked
* from either hardware interrupt or other context, with hardware interrupts
* either disabled or enabled.
void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason);
void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason);
/*
* It is not allowed to call kfree_skb() or consume_skb() from hardware
* interrupt context or with hardware interrupts being disabled.
* (in_irq() || irqs_disabled())
*
* We provide four helpers that can be used in following contexts :
*
* dev_kfree_skb_irq(skb) when caller drops a packet from irq context,
* replacing kfree_skb(skb)
*
* dev_consume_skb_irq(skb) when caller consumes a packet from irq context.
* Typically used in place of consume_skb(skb) in TX completion path
*
* dev_kfree_skb_any(skb) when caller doesn't know its current irq context,
* replacing kfree_skb(skb)
*
* dev_consume_skb_any(skb) when caller doesn't know its current irq context,
* and consumed a packet. Used in place of consume_skb(skb)
*/
void dev_kfree_skb_any(struct sk_buff *skb);
static inline void dev_kfree_skb_irq(struct sk_buff *skb)
{
__dev_kfree_skb_irq(skb, SKB_REASON_DROPPED);
}
static inline void dev_consume_skb_irq(struct sk_buff *skb)
{
__dev_kfree_skb_irq(skb, SKB_REASON_CONSUMED);
}
static inline void dev_kfree_skb_any(struct sk_buff *skb)
{
__dev_kfree_skb_any(skb, SKB_REASON_DROPPED);
}
static inline void dev_consume_skb_any(struct sk_buff *skb)
{
__dev_kfree_skb_any(skb, SKB_REASON_CONSUMED);
}
int netif_rx(struct sk_buff *skb);
int netif_rx_ni(struct sk_buff *skb);

49
net/core/dev.c
View File

@ -2145,30 +2145,42 @@ void __netif_schedule(struct Qdisc *q)
}
EXPORT_SYMBOL(__netif_schedule);
void dev_kfree_skb_irq(struct sk_buff *skb)
struct dev_kfree_skb_cb {
enum skb_free_reason reason;
};
static struct dev_kfree_skb_cb *get_kfree_skb_cb(const struct sk_buff *skb)
{
if (atomic_dec_and_test(&skb->users)) {
struct softnet_data *sd;
unsigned long flags;
local_irq_save(flags);
sd = &__get_cpu_var(softnet_data);
skb->next = sd->completion_queue;
sd->completion_queue = skb;
raise_softirq_irqoff(NET_TX_SOFTIRQ);
local_irq_restore(flags);
}
return (struct dev_kfree_skb_cb *)skb->cb;
}
EXPORT_SYMBOL(dev_kfree_skb_irq);
void dev_kfree_skb_any(struct sk_buff *skb)
void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
{
unsigned long flags;
if (likely(atomic_read(&skb->users) == 1)) {
smp_rmb();
atomic_set(&skb->users, 0);
} else if (likely(!atomic_dec_and_test(&skb->users))) {
return;
}
get_kfree_skb_cb(skb)->reason = reason;
local_irq_save(flags);
skb->next = __this_cpu_read(softnet_data.completion_queue);
__this_cpu_write(softnet_data.completion_queue, skb);
raise_softirq_irqoff(NET_TX_SOFTIRQ);
local_irq_restore(flags);
}
EXPORT_SYMBOL(__dev_kfree_skb_irq);
void __dev_kfree_skb_any(struct sk_buff *skb, enum skb_free_reason reason)
{
if (in_irq() || irqs_disabled())
dev_kfree_skb_irq(skb);
__dev_kfree_skb_irq(skb, reason);
else
dev_kfree_skb(skb);
}
EXPORT_SYMBOL(dev_kfree_skb_any);
EXPORT_SYMBOL(__dev_kfree_skb_any);
/**
@ -3306,7 +3318,10 @@ static void net_tx_action(struct softirq_action *h)
clist = clist->next;
WARN_ON(atomic_read(&skb->users));
trace_kfree_skb(skb, net_tx_action);
if (likely(get_kfree_skb_cb(skb)->reason == SKB_REASON_CONSUMED))
trace_consume_skb(skb);
else
trace_kfree_skb(skb, net_tx_action);
__kfree_skb(skb);
}
}