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Commit 15fad714 authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by David S. Miller
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net: bulk free SKBs that were delay free'ed due to IRQ context 



The network stack defers SKBs free, in-case free happens in IRQ or
when IRQs are disabled. This happens in __dev_kfree_skb_irq() that
writes SKBs that were free'ed during IRQ to the softirq completion
queue (softnet_data.completion_queue).

These SKBs are naturally delayed, and cleaned up during NET_TX_SOFTIRQ
in function net_tx_action().  Take advantage of this a use the skb
defer and flush API, as we are already in softirq context.

For modern drivers this rarely happens. Although most drivers do call
dev_kfree_skb_any(), which detects the situation and calls
__dev_kfree_skb_irq() when needed.  This due to netpoll can call from
IRQ context.

Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 795bb1c0

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -2407,6 +2407,7 @@ static inline struct sk_buff *napi_alloc_skb(struct napi_struct *napi, 
void napi_consume_skb(struct sk_buff *skb, int budget);



void __kfree_skb_flush(void);

void __kfree_skb_defer(struct sk_buff *skb);



/**

 * __dev_alloc_pages - allocate page for network Rx

net/core/dev.c

+7 −1
Original line number Diff line number Diff line
@@ -3829,8 +3829,14 @@ static void net_tx_action(struct softirq_action *h) 
				trace_consume_skb(skb);

			else

				trace_kfree_skb(skb, net_tx_action);



			if (skb->fclone != SKB_FCLONE_UNAVAILABLE)

				__kfree_skb(skb);

			else

				__kfree_skb_defer(skb);

		}



		__kfree_skb_flush();

	}



	if (sd->output_queue) {

net/core/skbuff.c

+6 −2
Original line number Diff line number Diff line
@@ -767,7 +767,7 @@ void __kfree_skb_flush(void) 
	}

}



static void __kfree_skb_defer(struct sk_buff *skb)

static inline void _kfree_skb_defer(struct sk_buff *skb)

{

	struct napi_alloc_cache *nc = this_cpu_ptr(&napi_alloc_cache);
@@ -789,6 +789,10 @@ static void __kfree_skb_defer(struct sk_buff *skb) 
		nc->skb_count = 0;

	}

}

void __kfree_skb_defer(struct sk_buff *skb)

{

	_kfree_skb_defer(skb);

}



void napi_consume_skb(struct sk_buff *skb, int budget)

{
@@ -814,7 +818,7 @@ void napi_consume_skb(struct sk_buff *skb, int budget) 
		return;

	}



	__kfree_skb_defer(skb);

	_kfree_skb_defer(skb);

}

EXPORT_SYMBOL(napi_consume_skb);