From patchwork Mon Aug 6 10:30:50 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Emelyanov X-Patchwork-Id: 175312 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id E954F2C0080 for ; Mon, 6 Aug 2012 20:30:58 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754125Ab2HFKa5 (ORCPT ); Mon, 6 Aug 2012 06:30:57 -0400 Received: from mailhub.sw.ru ([195.214.232.25]:29137 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751316Ab2HFKa4 (ORCPT ); Mon, 6 Aug 2012 06:30:56 -0400 Received: from [10.30.22.37] ([10.30.22.37]) (authenticated bits=0) by relay.sw.ru (8.13.4/8.13.4) with ESMTP id q76AUoX5010184 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 6 Aug 2012 14:30:51 +0400 (MSK) Message-ID: <501F9CDA.6040403@parallels.com> Date: Mon, 06 Aug 2012 14:30:50 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1 MIME-Version: 1.0 To: David Miller , Eric Dumazet , "Eric W. Biederman" , Linux Netdev List Subject: [PATCH 1/5] net: Don't use ifindices in hash fns References: <501F9CAF.3030605@parallels.com> In-Reply-To: <501F9CAF.3030605@parallels.com> Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Eric noticed, that when there will be devices with equal indices, some hash functions that use them will become less effective as they could. Fix this in advance by taking the net_device address into calculations instead of the device index. Since the net_device is always aligned in memory, shift the pointer to eliminate always zero bits (like we do it in net_hash_mix). This is true for arp and ndisc hash fns. The netlabel, can and llc ones are also ifindex-based, but that three are init_net-only, thus will not be affected. Signed-off-by: Pavel Emelyanov --- include/linux/netdevice.h | 6 ++++++ include/net/arp.h | 2 +- include/net/ndisc.h | 2 +- 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index a9db4f3..6010b37 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1330,6 +1330,12 @@ struct net_device { #define NETDEV_ALIGN 32 +static inline unsigned int netdev_hash_mix(const struct net_device *dev) +{ + return (unsigned int)(((unsigned long)dev) >> + max(L1_CACHE_BYTES, NETDEV_ALIGN)); +} + static inline int netdev_get_prio_tc_map(const struct net_device *dev, u32 prio) { diff --git a/include/net/arp.h b/include/net/arp.h index 7f7df93..0305a38 100644 --- a/include/net/arp.h +++ b/include/net/arp.h @@ -10,7 +10,7 @@ extern struct neigh_table arp_tbl; static inline u32 arp_hashfn(u32 key, const struct net_device *dev, u32 hash_rnd) { - u32 val = key ^ dev->ifindex; + u32 val = key ^ netdev_hash_mix(dev); return val * hash_rnd; } diff --git a/include/net/ndisc.h b/include/net/ndisc.h index 96a3b5c..ae7c1fd 100644 --- a/include/net/ndisc.h +++ b/include/net/ndisc.h @@ -134,7 +134,7 @@ static inline u32 ndisc_hashfn(const void *pkey, const struct net_device *dev, _ { const u32 *p32 = pkey; - return (((p32[0] ^ dev->ifindex) * hash_rnd[0]) + + return (((p32[0] ^ netdev_hash_mix(dev)) * hash_rnd[0]) + (p32[1] * hash_rnd[1]) + (p32[2] * hash_rnd[2]) + (p32[3] * hash_rnd[3]));