From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754466AbaIWJAA (ORCPT ); Tue, 23 Sep 2014 05:00:00 -0400 Received: from pegase1.c-s.fr ([93.17.236.30]:22319 "EHLO mailhub1.si.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753337AbaIWI74 (ORCPT ); Tue, 23 Sep 2014 04:59:56 -0400 From: Christophe Leroy To: "David S. Miller" CC: linux-kernel@vger.kernel.org, Eric Dumazet , netdev@vger.kernel.org Subject: [PATCH] net: optimise inet_proto_csum_replace4() Message-Id: <20140923085437.696B81AB26D@localhost.localdomain> Date: Tue, 23 Sep 2014 10:54:37 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- -- 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); -- 2.1.0