kernel-ark/net/ipv4/protocol.c
Eric Dumazet 03d4f879b9 [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>
2007-04-25 22:28:20 -07:00

99 lines
2.3 KiB
C

/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* INET protocol dispatch tables.
*
* Version: $Id: protocol.c,v 1.14 2001/05/18 02:25:49 davem Exp $
*
* Authors: Ross Biro
* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
*
* Fixes:
* Alan Cox : Ahah! udp icmp errors don't work because
* udp_err is never called!
* Alan Cox : Added new fields for init and ready for
* proper fragmentation (_NO_ 4K limits!)
* Richard Colella : Hang on hash collision
* Vince Laviano : Modified inet_del_protocol() to correctly
* maintain copy bit.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/timer.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/ipip.h>
#include <linux/igmp.h>
struct net_protocol *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
static DEFINE_SPINLOCK(inet_proto_lock);
/*
* Add a protocol handler to the hash tables
*/
int inet_add_protocol(struct net_protocol *prot, unsigned char protocol)
{
int hash, ret;
hash = protocol & (MAX_INET_PROTOS - 1);
spin_lock_bh(&inet_proto_lock);
if (inet_protos[hash]) {
ret = -1;
} else {
inet_protos[hash] = prot;
ret = 0;
}
spin_unlock_bh(&inet_proto_lock);
return ret;
}
/*
* Remove a protocol from the hash tables.
*/
int inet_del_protocol(struct net_protocol *prot, unsigned char protocol)
{
int hash, ret;
hash = protocol & (MAX_INET_PROTOS - 1);
spin_lock_bh(&inet_proto_lock);
if (inet_protos[hash] == prot) {
inet_protos[hash] = NULL;
ret = 0;
} else {
ret = -1;
}
spin_unlock_bh(&inet_proto_lock);
synchronize_net();
return ret;
}
EXPORT_SYMBOL(inet_add_protocol);
EXPORT_SYMBOL(inet_del_protocol);