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Commit e88721f8 authored by Krishna Kumar's avatar Krishna Kumar Committed by David S. Miller
Browse files

net: Optimize skb_tx_hash() by eliminating a comparison 



Optimize skb_tx_hash() by eliminating a comparison that executes for
every packet. skb_tx_hashrnd initialization is moved to a later part of
the startup sequence, namely after the "random" driver is initialized.

Rebooted the system three times and verified that the code generates
different random numbers each time.

Signed-off-by: default avatarKrishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 38bb045d

net/core/dev.c

+8 −6
Original line number Diff line number Diff line
@@ -1745,17 +1745,11 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev, 
}



static u32 skb_tx_hashrnd;

static int skb_tx_hashrnd_initialized = 0;



static u16 skb_tx_hash(struct net_device *dev, struct sk_buff *skb)

{

	u32 hash;



	if (unlikely(!skb_tx_hashrnd_initialized)) {

		get_random_bytes(&skb_tx_hashrnd, 4);

		skb_tx_hashrnd_initialized = 1;

	}



	if (skb_rx_queue_recorded(skb)) {

		hash = skb_get_rx_queue(skb);

	} else if (skb->sk && skb->sk->sk_hash) {
@@ -5291,6 +5285,14 @@ static int __init net_dev_init(void) 


subsys_initcall(net_dev_init);



static int __init initialize_hashrnd(void)

{

	get_random_bytes(&skb_tx_hashrnd, sizeof(skb_tx_hashrnd));

	return 0;

}



late_initcall_sync(initialize_hashrnd);



EXPORT_SYMBOL(__dev_get_by_index);

EXPORT_SYMBOL(__dev_get_by_name);

EXPORT_SYMBOL(__dev_remove_pack);