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: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 18bcaf2..d3dbb48 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -153,7 +153,7 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
#ifdef CONFIG_IP_FIB_TRIE_STATS
- t->stats.semantic_match_miss++;
+ this_cpu_inc(t->stats->semantic_match_miss);
#endif
}
@@ -1399,6 +1399,9 @@
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 @@
goto failed;
#ifdef CONFIG_IP_FIB_TRIE_STATS
- t->stats.gets++;
+ this_cpu_inc(stats->gets);
#endif
/* Just a leaf? */
@@ -1441,7 +1444,7 @@
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 @@
chopped_off = 0;
#ifdef CONFIG_IP_FIB_TRIE_STATS
- t->stats.backtrack++;
+ this_cpu_inc(stats->backtrack);
#endif
goto backtrace;
}
@@ -1830,6 +1833,11 @@
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 @@
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 @@
#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 @@
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
}
}