From e6247027e5173c00efb2084d688d06ff835bc3b0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 5 Dec 2013 04:45:08 -0800 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/linux/netdevice.h | 53 ++++++++++++++++++++++++++++++++------- net/core/dev.c | 45 ++++++++++++++++++++++----------- 2 files changed, 74 insertions(+), 24 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 7f0ed423a360..9d55e5188b96 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -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); diff --git a/net/core/dev.c b/net/core/dev.c index c98052487e98..6cc98dd49c7a 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -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; + 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); + 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); +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); /** @@ -3306,7 +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); } } -- 2.30.2