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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: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Krishna Kumar 2009-02-18 17:55:02 -08:00 committed by David S. Miller
parent 38bb045d49
commit e88721f87d
1 changed files with 8 additions and 6 deletions
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14
net/core/dev.c
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@ -1745,17 +1745,11 @@ out_kfree_skb:
}
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 @@ out:
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);