gro: Optimise TCP packet reception
gro: Optimise TCP packet reception
As this function can be called more than half a million times for
10GbE, it's important to optimise it as much as we can.
This patch uses bit ops to logical ops, as well as open coding
memcmp to exploit alignment properties.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 73266b7..90b2f3c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2478,9 +2478,9 @@
struct tcphdr *th2;
unsigned int thlen;
unsigned int flags;
- unsigned int total;
unsigned int mss = 1;
int flush = 1;
+ int i;
th = skb_gro_header(skb, sizeof(*th));
if (unlikely(!th))
@@ -2504,7 +2504,7 @@
th2 = tcp_hdr(p);
- if (th->source != th2->source || th->dest != th2->dest) {
+ if ((th->source ^ th2->source) | (th->dest ^ th2->dest)) {
NAPI_GRO_CB(p)->same_flow = 0;
continue;
}
@@ -2519,14 +2519,15 @@
flush |= flags & TCP_FLAG_CWR;
flush |= (flags ^ tcp_flag_word(th2)) &
~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH);
- flush |= th->ack_seq != th2->ack_seq || th->window != th2->window;
- flush |= memcmp(th + 1, th2 + 1, thlen - sizeof(*th));
+ flush |= (th->ack_seq ^ th2->ack_seq) | (th->window ^ th2->window);
+ for (i = sizeof(*th); !flush && i < thlen; i += 4)
+ flush |= *(u32 *)((u8 *)th + i) ^
+ *(u32 *)((u8 *)th2 + i);
- total = skb_gro_len(p);
mss = skb_shinfo(p)->gso_size;
- flush |= skb_gro_len(skb) > mss || !skb_gro_len(skb);
- flush |= ntohl(th2->seq) + total != ntohl(th->seq);
+ flush |= (skb_gro_len(skb) > mss) | !skb_gro_len(skb);
+ flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
if (flush || skb_gro_receive(head, skb)) {
mss = 1;
