From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH net-next] netns: reorder fields in struct net Date: Thu, 14 Oct 2010 17:56:18 +0200 Message-ID: <1287071778.2712.73.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev To: David Miller Return-path: Received: from mail-ww0-f47.google.com ([74.125.82.47]:58501 "EHLO mail-ww0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755268Ab0JNP4Y (ORCPT ); Thu, 14 Oct 2010 11:56:24 -0400 Received: by wwf26 with SMTP id 26so9292059wwf.4 for ; Thu, 14 Oct 2010 08:56:23 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: In a network bench, I noticed an unfortunate false sharing between 'loopback_dev' and 'count' fields in "struct net". 'count' is written each time a socket is created or destroyed, while loopback_dev might be often read in routing code. Move loopback_dev in a read mostly section of "struct net" Note: struct netns_xfrm is cache line aligned on SMP. (It contains a "struct dst_ops") Move it at the end to avoid holes, and reduce sizeof(struct net) by 128 bytes on ia32. Signed-off-by: Eric Dumazet --- include/net/net_namespace.h | 17 ++++++++++------- include/net/netns/xfrm.h | 9 +++++---- 2 files changed, 15 insertions(+), 11 deletions(-) diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index bd10a79..65af9a0 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -41,6 +41,8 @@ struct net { * destroy on demand */ #endif + spinlock_t rules_mod_lock; + struct list_head list; /* list of network namespaces */ struct list_head cleanup_list; /* namespaces on death row */ struct list_head exit_list; /* Use only net_mutex */ @@ -52,7 +54,8 @@ struct net { struct ctl_table_set sysctls; #endif - struct net_device *loopback_dev; /* The loopback */ + struct sock *rtnl; /* rtnetlink socket */ + struct sock *genl_sock; struct list_head dev_base_head; struct hlist_head *dev_name_head; @@ -60,11 +63,9 @@ struct net { /* core fib_rules */ struct list_head rules_ops; - spinlock_t rules_mod_lock; - struct sock *rtnl; /* rtnetlink socket */ - struct sock *genl_sock; + struct net_device *loopback_dev; /* The loopback */ struct netns_core core; struct netns_mib mib; struct netns_packet packet; @@ -84,13 +85,15 @@ struct net { struct sock *nfnl; struct sock *nfnl_stash; #endif -#ifdef CONFIG_XFRM - struct netns_xfrm xfrm; -#endif #ifdef CONFIG_WEXT_CORE struct sk_buff_head wext_nlevents; #endif struct net_generic *gen; + + /* Note : following structs are cache line aligned */ +#ifdef CONFIG_XFRM + struct netns_xfrm xfrm; +#endif }; diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h index 74f119a..748f91f 100644 --- a/include/net/netns/xfrm.h +++ b/include/net/netns/xfrm.h @@ -43,10 +43,6 @@ struct netns_xfrm { unsigned int policy_count[XFRM_POLICY_MAX * 2]; struct work_struct policy_hash_work; - struct dst_ops xfrm4_dst_ops; -#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) - struct dst_ops xfrm6_dst_ops; -#endif struct sock *nlsk; struct sock *nlsk_stash; @@ -58,6 +54,11 @@ struct netns_xfrm { #ifdef CONFIG_SYSCTL struct ctl_table_header *sysctl_hdr; #endif + + struct dst_ops xfrm4_dst_ops; +#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) + struct dst_ops xfrm6_dst_ops; +#endif }; #endif