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ipv6: gro: do not use slow memcmp() in ipv6_gro_receive()

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ipv6_gro_receive() compares 34 bytes using slow memcmp(),
while handcoding with a couple of ipv6_addr_equal() is much faster.

Before this patch, "perf top -e cycles:pp -C <cpu>" would
see memcmp() using ~10% of cpu cycles on a 40Gbit NIC
receiving IPv6 TCP traffic.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2018-11-06 14:25:52 -08:00 committed by David S. Miller
parent 5e1abdc3fe
commit 0b215b9798
1 changed files with 10 additions and 3 deletions
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13
net/ipv6/ip6_offload.c
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@ -229,14 +229,21 @@ static struct sk_buff *ipv6_gro_receive(struct list_head *head,
* XXX skbs on the gro_list have all been parsed and pulled * XXX skbs on the gro_list have all been parsed and pulled
* already so we don't need to compare nlen * already so we don't need to compare nlen
* (nlen != (sizeof(*iph2) + ipv6_exthdrs_len(iph2, &ops))) * (nlen != (sizeof(*iph2) + ipv6_exthdrs_len(iph2, &ops)))
* memcmp() alone below is suffcient, right? * memcmp() alone below is sufficient, right?
*/ */
if ((first_word & htonl(0xF00FFFFF)) || if ((first_word & htonl(0xF00FFFFF)) ||
memcmp(&iph->nexthdr, &iph2->nexthdr, !ipv6_addr_equal(&iph->saddr, &iph2->saddr) ||
nlen - offsetof(struct ipv6hdr, nexthdr))) { !ipv6_addr_equal(&iph->daddr, &iph2->daddr) ||
*(u16 *)&iph->nexthdr != *(u16 *)&iph2->nexthdr) {
not_same_flow:
NAPI_GRO_CB(p)->same_flow = 0; NAPI_GRO_CB(p)->same_flow = 0;
continue; continue;
} }
if (unlikely(nlen > sizeof(struct ipv6hdr))) {
if (memcmp(iph + 1, iph2 + 1,
nlen - sizeof(struct ipv6hdr)))
goto not_same_flow;
}
/* flush if Traffic Class fields are different */ /* flush if Traffic Class fields are different */
NAPI_GRO_CB(p)->flush |= !!(first_word & htonl(0x0FF00000)); NAPI_GRO_CB(p)->flush |= !!(first_word & htonl(0x0FF00000));
NAPI_GRO_CB(p)->flush |= flush; NAPI_GRO_CB(p)->flush |= flush;