Commit 0b4cec8c authored Jan 15, 2014 by Tom Herbert Committed by David S. Miller Jan 16, 2014

net: Check skb->rxhash in gro_receive



When initializing a gro_list for a packet, first check the rxhash of
the incoming skb against that of the skb's in the list. This should be
a very strong inidicator of whether the flow is going to be matched,
and potentially allows a lot of other checks to be short circuited.
Use skb_hash_raw so that we don't force the hash to be calculated.

Tested by running netperf 200 TCP_STREAMs between two machines with
GRO, HW rxhash, and 1G. Saw no performance degration, slight reduction
of time in dev_gro_receive.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 57bdf7f4

net/core/dev.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -3821,10 +3821,18 @@ static void gro_list_prepare(struct napi_struct napi, struct sk_buff skb)
		{
		struct sk_buff *p;
		unsigned int maclen = skb->dev->hard_header_len;
		u32 hash = skb_get_hash_raw(skb);

		for (p = napi->gro_list; p; p = p->next) {
		unsigned long diffs;

		NAPI_GRO_CB(p)->flush = 0;

		if (hash != skb_get_hash_raw(p)) {
		NAPI_GRO_CB(p)->same_flow = 0;
		continue;
		}

		diffs = (unsigned long)p->dev ^ (unsigned long)skb->dev;
		diffs \|= p->vlan_tci ^ skb->vlan_tci;
		if (maclen == ETH_HLEN)
		@@ -3835,7 +3843,6 @@ static void gro_list_prepare(struct napi_struct napi, struct sk_buff skb)
		skb_gro_mac_header(skb),
		maclen);
		NAPI_GRO_CB(p)->same_flow = !diffs;
		NAPI_GRO_CB(p)->flush = 0;
		}
		}