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Commit e9897071 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

igmp: hash a hash table to speedup ip_check_mc_rcu() 



After IP route cache removal, multicast applications using
a lot of multicast addresses hit a O(N) behavior in ip_check_mc_rcu()

Add a per in_device hash table to get faster lookup.

This hash table is created only if the number of items in mc_list is
above 4.

Reported-by: default avatarShawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Tested-by: default avatarShawn Bohrer <sbohrer@rgmadvisors.com>
Reviewed-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 64153ce0

include/linux/igmp.h

+1 −0
Original line number Diff line number Diff line
@@ -84,6 +84,7 @@ struct ip_mc_list { 
		struct ip_mc_list *next;

		struct ip_mc_list __rcu *next_rcu;

	};

	struct ip_mc_list __rcu *next_hash;

	struct timer_list	timer;

	int			users;

	atomic_t		refcnt;

include/linux/inetdevice.h

+5 −0
Original line number Diff line number Diff line
@@ -50,12 +50,17 @@ struct ipv4_devconf { 
	DECLARE_BITMAP(state, IPV4_DEVCONF_MAX);

};



#define MC_HASH_SZ_LOG 9



struct in_device {

	struct net_device	*dev;

	atomic_t		refcnt;

	int			dead;

	struct in_ifaddr	*ifa_list;	/* IP ifaddr chain		*/



	struct ip_mc_list __rcu	*mc_list;	/* IP multicast filter chain    */

	struct ip_mc_list __rcu	* __rcu *mc_hash;



	int			mc_count;	/* Number of installed mcasts	*/

	spinlock_t		mc_tomb_lock;

	struct ip_mc_list	*mc_tomb;

net/ipv4/devinet.c

+1 −0
Original line number Diff line number Diff line
@@ -215,6 +215,7 @@ void in_dev_finish_destroy(struct in_device *idev) 


	WARN_ON(idev->ifa_list);

	WARN_ON(idev->mc_list);

	kfree(rcu_dereference_protected(idev->mc_hash, 1));

#ifdef NET_REFCNT_DEBUG

	pr_debug("%s: %p=%s\n", __func__, idev, dev ? dev->name : "NIL");

#endif

net/ipv4/igmp.c

+70 −3
Original line number Diff line number Diff line
@@ -1217,6 +1217,57 @@ static void igmp_group_added(struct ip_mc_list *im) 
 *	Multicast list managers

 */



static u32 ip_mc_hash(const struct ip_mc_list *im)

{

	return hash_32((u32)im->multiaddr, MC_HASH_SZ_LOG);

}



static void ip_mc_hash_add(struct in_device *in_dev,

			   struct ip_mc_list *im)

{

	struct ip_mc_list __rcu **mc_hash;

	u32 hash;



	mc_hash = rtnl_dereference(in_dev->mc_hash);

	if (mc_hash) {

		hash = ip_mc_hash(im);

		im->next_hash = rtnl_dereference(mc_hash[hash]);

		rcu_assign_pointer(mc_hash[hash], im);

		return;

	}



	/* do not use a hash table for small number of items */

	if (in_dev->mc_count < 4)

		return;



	mc_hash = kzalloc(sizeof(struct ip_mc_list *) << MC_HASH_SZ_LOG,

			  GFP_KERNEL);

	if (!mc_hash)

		return;



	for_each_pmc_rtnl(in_dev, im) {

		hash = ip_mc_hash(im);

		im->next_hash = rtnl_dereference(mc_hash[hash]);

		RCU_INIT_POINTER(mc_hash[hash], im);

	}



	rcu_assign_pointer(in_dev->mc_hash, mc_hash);

}



static void ip_mc_hash_remove(struct in_device *in_dev,

			      struct ip_mc_list *im)

{

	struct ip_mc_list __rcu **mc_hash = rtnl_dereference(in_dev->mc_hash);

	struct ip_mc_list *aux;



	if (!mc_hash)

		return;

	mc_hash += ip_mc_hash(im);

	while ((aux = rtnl_dereference(*mc_hash)) != im)

		mc_hash = &aux->next_hash;

	*mc_hash = im->next_hash;

}





/*

 *	A socket has joined a multicast group on device dev.
@@ -1258,6 +1309,8 @@ void ip_mc_inc_group(struct in_device *in_dev, __be32 addr) 
	in_dev->mc_count++;

	rcu_assign_pointer(in_dev->mc_list, im);



	ip_mc_hash_add(in_dev, im);



#ifdef CONFIG_IP_MULTICAST

	igmpv3_del_delrec(in_dev, im->multiaddr);

#endif
@@ -1314,6 +1367,7 @@ void ip_mc_dec_group(struct in_device *in_dev, __be32 addr) 
	     ip = &i->next_rcu) {

		if (i->multiaddr == addr) {

			if (--i->users == 0) {

				ip_mc_hash_remove(in_dev, i);

				*ip = i->next_rcu;

				in_dev->mc_count--;

				igmp_group_dropped(i);
@@ -2321,13 +2375,26 @@ void ip_mc_drop_socket(struct sock *sk) 
int ip_check_mc_rcu(struct in_device *in_dev, __be32 mc_addr, __be32 src_addr, u16 proto)

{

	struct ip_mc_list *im;

	struct ip_mc_list __rcu **mc_hash;

	struct ip_sf_list *psf;

	int rv = 0;



	mc_hash = rcu_dereference(in_dev->mc_hash);

	if (mc_hash) {

		u32 hash = hash_32((u32)mc_addr, MC_HASH_SZ_LOG);



		for (im = rcu_dereference(mc_hash[hash]);

		     im != NULL;

		     im = rcu_dereference(im->next_hash)) {

			if (im->multiaddr == mc_addr)

				break;

		}

	} else {

		for_each_pmc_rcu(in_dev, im) {

			if (im->multiaddr == mc_addr)

				break;

		}

	}

	if (im && proto == IPPROTO_IGMP) {

		rv = 1;

	} else if (im) {