Commit 8274a97a authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
Browse files

fib_trie: Update usage stats to be percpu instead of global variables 



The trie usage stats were currently being shared by all threads that were
calling fib_table_lookup.  As a result when multiple threads were
performing lookups simultaneously the trie would begin to cache bounce
between those threads.

In order to prevent this I have updated the usage stats to use a set of
percpu variables.  By doing this we should be able to avoid the cache
bouncing and still make use of these stats.

Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bec94d43

net/ipv4/fib_frontend.c

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ static int __net_init fib4_rules_init(struct net *net) 
	return 0;



fail:

	kfree(local_table);

	fib_free_table(local_table);

	return -ENOMEM;

}

#else

net/ipv4/fib_trie.c

+48 −20
Original line number Diff line number Diff line
@@ -153,7 +153,7 @@ struct trie_stat { 
struct trie {

	struct rt_trie_node __rcu *trie;

#ifdef CONFIG_IP_FIB_TRIE_STATS

	struct trie_use_stats stats;

	struct trie_use_stats __percpu *stats;

#endif

};
@@ -631,7 +631,7 @@ static struct rt_trie_node *resize(struct trie *t, struct tnode *tn) 
		if (IS_ERR(tn)) {

			tn = old_tn;

#ifdef CONFIG_IP_FIB_TRIE_STATS

			t->stats.resize_node_skipped++;

			this_cpu_inc(t->stats->resize_node_skipped);

#endif

			break;

		}
@@ -658,7 +658,7 @@ static struct rt_trie_node *resize(struct trie *t, struct tnode *tn) 
		if (IS_ERR(tn)) {

			tn = old_tn;

#ifdef CONFIG_IP_FIB_TRIE_STATS

			t->stats.resize_node_skipped++;

			this_cpu_inc(t->stats->resize_node_skipped);

#endif

			break;

		}
@@ -1357,7 +1357,7 @@ static int check_leaf(struct fib_table *tb, struct trie *t, struct leaf *l, 
			err = fib_props[fa->fa_type].error;

			if (err) {

#ifdef CONFIG_IP_FIB_TRIE_STATS

				t->stats.semantic_match_passed++;

				this_cpu_inc(t->stats->semantic_match_passed);

#endif

				return err;

			}
@@ -1372,7 +1372,7 @@ static int check_leaf(struct fib_table *tb, struct trie *t, struct leaf *l, 
					continue;



#ifdef CONFIG_IP_FIB_TRIE_STATS

				t->stats.semantic_match_passed++;

				this_cpu_inc(t->stats->semantic_match_passed);

#endif

				res->prefixlen = li->plen;

				res->nh_sel = nhsel;
@@ -1388,7 +1388,7 @@ static int check_leaf(struct fib_table *tb, struct trie *t, struct leaf *l, 
		}



#ifdef CONFIG_IP_FIB_TRIE_STATS

		t->stats.semantic_match_miss++;

		this_cpu_inc(t->stats->semantic_match_miss);

#endif

	}
@@ -1399,6 +1399,9 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, 
		     struct fib_result *res, int fib_flags)

{

	struct trie *t = (struct trie *) tb->tb_data;

#ifdef CONFIG_IP_FIB_TRIE_STATS

	struct trie_use_stats __percpu *stats = t->stats;

#endif

	int ret;

	struct rt_trie_node *n;

	struct tnode *pn;
@@ -1417,7 +1420,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, 
		goto failed;



#ifdef CONFIG_IP_FIB_TRIE_STATS

	t->stats.gets++;

	this_cpu_inc(stats->gets);

#endif



	/* Just a leaf? */
@@ -1441,7 +1444,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, 


		if (n == NULL) {

#ifdef CONFIG_IP_FIB_TRIE_STATS

			t->stats.null_node_hit++;

			this_cpu_inc(stats->null_node_hit);

#endif

			goto backtrace;

		}
@@ -1576,7 +1579,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp, 
			chopped_off = 0;



#ifdef CONFIG_IP_FIB_TRIE_STATS

			t->stats.backtrack++;

			this_cpu_inc(stats->backtrack);

#endif

			goto backtrace;

		}
@@ -1830,6 +1833,11 @@ int fib_table_flush(struct fib_table *tb) 


void fib_free_table(struct fib_table *tb)

{

#ifdef CONFIG_IP_FIB_TRIE_STATS

	struct trie *t = (struct trie *)tb->tb_data;



	free_percpu(t->stats);

#endif /* CONFIG_IP_FIB_TRIE_STATS */

	kfree(tb);

}
@@ -1973,7 +1981,14 @@ struct fib_table *fib_trie_table(u32 id) 
	tb->tb_num_default = 0;



	t = (struct trie *) tb->tb_data;

	memset(t, 0, sizeof(*t));

	RCU_INIT_POINTER(t->trie, NULL);

#ifdef CONFIG_IP_FIB_TRIE_STATS

	t->stats = alloc_percpu(struct trie_use_stats);

	if (!t->stats) {

		kfree(tb);

		tb = NULL;

	}

#endif



	return tb;

}
@@ -2139,18 +2154,31 @@ static void trie_show_stats(struct seq_file *seq, struct trie_stat *stat) 


#ifdef CONFIG_IP_FIB_TRIE_STATS

static void trie_show_usage(struct seq_file *seq,

			    const struct trie_use_stats *stats)

			    const struct trie_use_stats __percpu *stats)

{

	struct trie_use_stats s = { 0 };

	int cpu;



	/* loop through all of the CPUs and gather up the stats */

	for_each_possible_cpu(cpu) {

		const struct trie_use_stats *pcpu = per_cpu_ptr(stats, cpu);



		s.gets += pcpu->gets;

		s.backtrack += pcpu->backtrack;

		s.semantic_match_passed += pcpu->semantic_match_passed;

		s.semantic_match_miss += pcpu->semantic_match_miss;

		s.null_node_hit += pcpu->null_node_hit;

		s.resize_node_skipped += pcpu->resize_node_skipped;

	}



	seq_printf(seq, "\nCounters:\n---------\n");

	seq_printf(seq, "gets = %u\n", stats->gets);

	seq_printf(seq, "backtracks = %u\n", stats->backtrack);

	seq_printf(seq, "gets = %u\n", s.gets);

	seq_printf(seq, "backtracks = %u\n", s.backtrack);

	seq_printf(seq, "semantic match passed = %u\n",

		   stats->semantic_match_passed);

	seq_printf(seq, "semantic match miss = %u\n",

		   stats->semantic_match_miss);

	seq_printf(seq, "null node hit= %u\n", stats->null_node_hit);

	seq_printf(seq, "skipped node resize = %u\n\n",

		   stats->resize_node_skipped);

		   s.semantic_match_passed);

	seq_printf(seq, "semantic match miss = %u\n", s.semantic_match_miss);

	seq_printf(seq, "null node hit= %u\n", s.null_node_hit);

	seq_printf(seq, "skipped node resize = %u\n\n", s.resize_node_skipped);

}

#endif /*  CONFIG_IP_FIB_TRIE_STATS */
@@ -2191,7 +2219,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v) 
			trie_collect_stats(t, &stat);

			trie_show_stats(seq, &stat);

#ifdef CONFIG_IP_FIB_TRIE_STATS

			trie_show_usage(seq, &t->stats);

			trie_show_usage(seq, t->stats);

#endif

		}

	}