[IPV4]: align inet_protos[] on SMP
authorEric Dumazet <dada1@cosmosbay.com>
Tue, 27 Mar 2007 21:18:34 +0000 (14:18 -0700)
committerDavid S. Miller <davem@sunset.davemloft.net>
Thu, 26 Apr 2007 05:28:20 +0000 (22:28 -0700)
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>
net/ipv4/protocol.c

index da70fef..971ab93 100644 (file)
@@ -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);
 
 /*