net: Optimize skb_tx_hash() by eliminating a comparison (e88721f8) · Commits · 戴 / test

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>

net/core/dev.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -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);

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