From 58e3cac5613aa01720e55637d8f1c966a25c3202 Mon Sep 17 00:00:00 2001 From: LEROY Christophe Date: Tue, 23 Sep 2014 10:54:37 +0200 Subject: [PATCH] net: optimise inet_proto_csum_replace4() csum_partial() is a generic function which is not optimised for small fixed length calculations, and its use requires to store "from" and "to" values in memory while we already have them available in registers. This also has impact, especially on RISC processors. In the same spirit as the change done by Eric Dumazet on csum_replace2(), this patch rewrites inet_proto_csum_replace4() taking into account RFC1624. I spotted during a NATted tcp transfert that csum_partial() is one of top 5 consuming functions (around 8%), and the second user of csum_partial() is inet_proto_csum_replace4(). Signed-off-by: Christophe Leroy Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/utils.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/net/core/utils.c b/net/core/utils.c index eed3433..efc76dd 100644 --- a/net/core/utils.c +++ b/net/core/utils.c @@ -306,16 +306,14 @@ EXPORT_SYMBOL(in6_pton); void inet_proto_csum_replace4(__sum16 *sum, struct sk_buff *skb, __be32 from, __be32 to, int pseudohdr) { - __be32 diff[] = { ~from, to }; if (skb->ip_summed != CHECKSUM_PARTIAL) { - *sum = csum_fold(csum_partial(diff, sizeof(diff), - ~csum_unfold(*sum))); + *sum = csum_fold(csum_add(csum_sub(~csum_unfold(*sum), from), + to)); if (skb->ip_summed == CHECKSUM_COMPLETE && pseudohdr) - skb->csum = ~csum_partial(diff, sizeof(diff), - ~skb->csum); + skb->csum = ~csum_add(csum_sub(~(skb->csum), from), to); } else if (pseudohdr) - *sum = ~csum_fold(csum_partial(diff, sizeof(diff), - csum_unfold(*sum))); + *sum = ~csum_fold(csum_add(csum_sub(csum_unfold(*sum), from), + to)); } EXPORT_SYMBOL(inet_proto_csum_replace4); -- 2.7.4