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Commit 3df97ba8 authored Apr 25, 2016 by Jason Wang Committed by David S. Miller Apr 28, 2016

tuntap: calculate rps hash only when needed



There's no need to calculate rps hash if it was not enabled. So this
patch export rps_needed and check it before trying to get rps
hash. Tests (using pktgen to inject packets to guest) shows this can
improve pps about 13% (when rps is disabled).

Before:
~1150000 pps
After:
~1300000 pps

Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
----
Changes from V1:
- Fix build when CONFIG_RPS is not set
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f345c9a5

drivers/net/tun.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -833,7 +833,8 @@ static netdev_tx_t tun_net_xmit(struct sk_buff skb, struct net_device dev)
		if (txq >= numqueues)
		goto drop;

		if (numqueues == 1) {
		#ifdef CONFIG_RPS
		if (numqueues == 1 && static_key_false(&rps_needed)) {
		/* Select queue was not called for the skbuff, so we extract the
		* RPS hash and save it into the flow_table here.
		*/
		@@ -848,6 +849,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff skb, struct net_device dev)
		tun_flow_save_rps_rxhash(e, rxhash);
		}
		}
		#endif

		tun_debug(KERN_INFO, tun, "tun_net_xmit %d\n", skb->len);

net/core/dev.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -3469,6 +3469,7 @@ u32 rps_cpu_mask __read_mostly;
		EXPORT_SYMBOL(rps_cpu_mask);

		struct static_key rps_needed __read_mostly;
		EXPORT_SYMBOL(rps_needed);

		static struct rps_dev_flow *
		set_rps_cpu(struct net_device dev, struct sk_buff skb,