Commit a6501e08 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

[IPV4] FIB_HASH: Reduce memory needs and speedup lookups 



Currently, sizeof(struct fib_alias) is 24 or 48 bytes on 32/64 bits
arches.

Because of SLAB_HWCACHE_ALIGN requirement, these are rounded to 32 and
64 bytes respectively.

This patch moves rcu to the end of fib_alias, and conditionally
defines it only for CONFIG_IP_FIB_TRIE.

We also remove SLAB_HWCACHE_ALIGN requirement for fib_alias and
fib_node objects because it is not necessary.

(BTW SLUB currently denies it for objects smaller than
cache_line_size() / 2, but not SLAB)

Finally, sizeof(fib_alias) go back to 16 and 32 bytes.

Then, we can embed one fib_alias on each fib_node, to favor locality.
Most of the time access to the fib_alias will be free because one
cache line contains both the list head (fn_alias) and (one of) the
list element.

Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b59cfbf7

net/ipv4/fib_hash.c

+20 −13
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ struct fib_node { 
	struct hlist_node	fn_hash;

	struct list_head	fn_alias;

	__be32			fn_key;

	struct fib_alias        fn_embedded_alias;

};



struct fn_zone {
@@ -193,9 +194,12 @@ static inline void fn_free_node(struct fib_node * f) 
	kmem_cache_free(fn_hash_kmem, f);

}



static inline void fn_free_alias(struct fib_alias *fa)

static inline void fn_free_alias(struct fib_alias *fa, struct fib_node *f)

{

	fib_release_info(fa->fa_info);

	if (fa == &f->fn_embedded_alias)

		fa->fa_info = NULL;

	else

		kmem_cache_free(fn_alias_kmem, fa);

}
@@ -476,15 +480,12 @@ static int fn_hash_insert(struct fib_table *tb, struct fib_config *cfg) 
		goto out;



	err = -ENOBUFS;

	new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);

	if (new_fa == NULL)

		goto out;



	new_f = NULL;

	if (!f) {

		new_f = kmem_cache_alloc(fn_hash_kmem, GFP_KERNEL);

		new_f = kmem_cache_zalloc(fn_hash_kmem, GFP_KERNEL);

		if (new_f == NULL)

			goto out_free_new_fa;

			goto out;



		INIT_HLIST_NODE(&new_f->fn_hash);

		INIT_LIST_HEAD(&new_f->fn_alias);
@@ -492,6 +493,12 @@ static int fn_hash_insert(struct fib_table *tb, struct fib_config *cfg) 
		f = new_f;

	}



	new_fa = &f->fn_embedded_alias;

	if (new_fa->fa_info != NULL) {

		new_fa = kmem_cache_alloc(fn_alias_kmem, GFP_KERNEL);

		if (new_fa == NULL)

			goto out_free_new_f;

	}

	new_fa->fa_info = fi;

	new_fa->fa_tos = tos;

	new_fa->fa_type = cfg->fc_type;
@@ -518,8 +525,8 @@ static int fn_hash_insert(struct fib_table *tb, struct fib_config *cfg) 
		  &cfg->fc_nlinfo, 0);

	return 0;



out_free_new_fa:

	kmem_cache_free(fn_alias_kmem, new_fa);

out_free_new_f:

	kmem_cache_free(fn_hash_kmem, new_f);

out:

	fib_release_info(fi);

	return err;
@@ -595,7 +602,7 @@ static int fn_hash_delete(struct fib_table *tb, struct fib_config *cfg) 


		if (fa->fa_state & FA_S_ACCESSED)

			rt_cache_flush(-1);

		fn_free_alias(fa);

		fn_free_alias(fa, f);

		if (kill_fn) {

			fn_free_node(f);

			fz->fz_nent--;
@@ -631,7 +638,7 @@ static int fn_flush_list(struct fn_zone *fz, int idx) 
				fib_hash_genid++;

				write_unlock_bh(&fib_hash_lock);



				fn_free_alias(fa);

				fn_free_alias(fa, f);

				found++;

			}

		}
@@ -750,10 +757,10 @@ static int fn_hash_dump(struct fib_table *tb, struct sk_buff *skb, struct netlin 
void __init fib_hash_init(void)

{

	fn_hash_kmem = kmem_cache_create("ip_fib_hash", sizeof(struct fib_node),

					 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);

					 0, SLAB_PANIC, NULL);



	fn_alias_kmem = kmem_cache_create("ip_fib_alias", sizeof(struct fib_alias),

					  0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);

					  0, SLAB_PANIC, NULL);



}

net/ipv4/fib_lookup.h

+3 −1
Original line number Diff line number Diff line
@@ -7,12 +7,14 @@ 


struct fib_alias {

	struct list_head	fa_list;

	struct rcu_head rcu;

	struct fib_info		*fa_info;

	u8			fa_tos;

	u8			fa_type;

	u8			fa_scope;

	u8			fa_state;

#ifdef CONFIG_IP_FIB_TRIE

	struct rcu_head		rcu;

#endif

};



#define FA_S_ACCESSED	0x01

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