Commit e6247027 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f96eb74c

include/linux/netdevice.h

+44 −9
Original line number Diff line number Diff line
@@ -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,

};



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);



/* Use this variant in places where it could be invoked

 * from either hardware interrupt or other context, with hardware interrupts

 * either disabled or enabled.

/*

 * 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);

net/core/dev.c

+30 −15
Original line number Diff line number Diff line
@@ -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)

{

	return (struct dev_kfree_skb_cb *)skb->cb;

}



void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)

{

	if (atomic_dec_and_test(&skb->users)) {

		struct softnet_data *sd;

	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);

		sd = &__get_cpu_var(softnet_data);

		skb->next = sd->completion_queue;

		sd->completion_queue = skb;

	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);

EXPORT_SYMBOL(__dev_kfree_skb_irq);



void dev_kfree_skb_any(struct sk_buff *skb)

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);





/**
@@ -3306,6 +3318,9 @@ static void net_tx_action(struct softirq_action *h) 
			clist = clist->next;



			WARN_ON(atomic_read(&skb->users));

			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);

		}

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