From: Eric Dumazet <dada1@cosmosbay.com>
Date: Tue, 27 Mar 2007 21:18:34 +0000 (-0700)
Subject: [IPV4]: align inet_protos[] on SMP
X-Git-Tag: v2.6.22-rc1~1128^2~151
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=03d4f879b9ddf7d5c1f788792247e62450342eed;p=linux-2.6

[IPV4]: align inet_protos[] on SMP

As IPPROTO_TCP is 6, it makes sense to make sure inet_protos[] array
is properly cache line aligned to avoid false sharing on SMP.

c0680540 b peer_total
c0680544 b inet_peer_unused_head
c0680560 B inet_protos

On i386 this example, we can see that inet_protos[IPPROTO_TCP] shares
a potentially hot (and modified) cache line.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/protocol.c b/net/ipv4/protocol.c
index da70fef82c..971ab9356e 100644
--- a/net/ipv4/protocol.c
+++ b/net/ipv4/protocol.c
@@ -45,7 +45,7 @@
 #include <net/ipip.h>
 #include <linux/igmp.h>
 
-struct net_protocol *inet_protos[MAX_INET_PROTOS];
+struct net_protocol *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
 static DEFINE_SPINLOCK(inet_proto_lock);
 
 /*