netdev - [PATCH net-next 2/9] inet: shrink netns

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Date:   Wed, 31 Mar 2021 10:52:06 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 2/9] inet: shrink netns_ipv4 by another cache line

From: Eric Dumazet <edumazet@...gle.com>

By shuffling around some fields to remove 8 bytes of hole,
we can save one cache line.

pahole result before/after the patch :

/* size: 768, cachelines: 12, members: 139 */
/* sum members: 673, holes: 11, sum holes: 39 */
/* padding: 56 */
/* paddings: 2, sum paddings: 7 */
/* forced alignments: 1 */

->

/* size: 704, cachelines: 11, members: 139 */
/* sum members: 673, holes: 10, sum holes: 31 */
/* paddings: 2, sum paddings: 7 */
/* forced alignments: 1 */

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/netns/ipv4.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 1085ed4e0788d7cd432dfc7e5604ef3cd66dc337..538ed69919dc4d51acfd43c7d6d1fca611fcb003 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -57,17 +57,17 @@ struct netns_ipv4 {
 	struct mutex		ra_mutex;
 #ifdef CONFIG_IP_MULTIPLE_TABLES
 	struct fib_rules_ops	*rules_ops;
-	bool			fib_has_custom_rules;
-	unsigned int		fib_rules_require_fldissect;
 	struct fib_table __rcu	*fib_main;
 	struct fib_table __rcu	*fib_default;
+	unsigned int		fib_rules_require_fldissect;
+	bool			fib_has_custom_rules;
 #endif
 	bool			fib_has_custom_local_routes;
+	bool			fib_offload_disabled;
 #ifdef CONFIG_IP_ROUTE_CLASSID
 	int			fib_num_tclassid_users;
 #endif
 	struct hlist_head	*fib_table_hash;
-	bool			fib_offload_disabled;
 	struct sock		*fibnl;
 
 	struct sock  * __percpu	*icmp_sk;
-- 
2.31.0.291.g576ba9dcdaf-goog