openvswitch: use percpu flow stats

Instead of using flow stats per NUMA node, use it per CPU. When using
megaflows, the stats lock can be a bottleneck in scalability.

On a E5-2690 12-core system, usual throughput went from ~4Mpps to
~15Mpps when forwarding between two 40GbE ports with a single flow
configured on the datapath.

This has been tested on a system with possible CPUs 0-7,16-23. After
module removal, there were no corruption on the slab cache.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
Cc: pravin shelar <pshelar@ovn.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 20 deletions

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 5b80612df182..0fa45439def1 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -29,6 +29,7 @@
 #include <linux/module.h>
 #include <linux/in.h>
 #include <linux/rcupdate.h>
+#include <linux/cpumask.h>
 #include <linux/if_arp.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
@@ -72,32 +73,33 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 {
 	struct flow_stats *stats;
 	int node = numa_node_id();
+	int cpu = smp_processor_id();
 	int len = skb->len + (skb_vlan_tag_present(skb) ? VLAN_HLEN : 0);
 
-	stats = rcu_dereference(flow->stats[node]);
+	stats = rcu_dereference(flow->stats[cpu]);
 
-	/* Check if already have node-specific stats. */
+	/* Check if already have CPU-specific stats. */
 	if (likely(stats)) {
 		spin_lock(&stats->lock);
 		/* Mark if we write on the pre-allocated stats. */
-		if (node == 0 && unlikely(flow->stats_last_writer != node))
-			flow->stats_last_writer = node;
+		if (cpu == 0 && unlikely(flow->stats_last_writer != cpu))
+			flow->stats_last_writer = cpu;
 	} else {
 		stats = rcu_dereference(flow->stats[0]); /* Pre-allocated. */
 		spin_lock(&stats->lock);
 
-		/* If the current NUMA-node is the only writer on the
+		/* If the current CPU is the only writer on the
 		 * pre-allocated stats keep using them.
 		 */
-		if (unlikely(flow->stats_last_writer != node)) {
+		if (unlikely(flow->stats_last_writer != cpu)) {
 			/* A previous locker may have already allocated the
-			 * stats, so we need to check again.  If node-specific
+			 * stats, so we need to check again.  If CPU-specific
 			 * stats were already allocated, we update the pre-
 			 * allocated stats as we have already locked them.
 			 */
-			if (likely(flow->stats_last_writer != NUMA_NO_NODE)
-			    && likely(!rcu_access_pointer(flow->stats[node]))) {
-				/* Try to allocate node-specific stats. */
+			if (likely(flow->stats_last_writer != -1) &&
+			    likely(!rcu_access_pointer(flow->stats[cpu]))) {
+				/* Try to allocate CPU-specific stats. */
 				struct flow_stats *new_stats;
 
 				new_stats =
@@ -114,12 +116,12 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 					new_stats->tcp_flags = tcp_flags;
 					spin_lock_init(&new_stats->lock);
 
-					rcu_assign_pointer(flow->stats[node],
+					rcu_assign_pointer(flow->stats[cpu],
 							   new_stats);
 					goto unlock;
 				}
 			}
-			flow->stats_last_writer = node;
+			flow->stats_last_writer = cpu;
 		}
 	}
 
@@ -136,15 +138,15 @@ void ovs_flow_stats_get(const struct sw_flow *flow,
 			struct ovs_flow_stats *ovs_stats,
 			unsigned long *used, __be16 *tcp_flags)
 {
-	int node;
+	int cpu;
 
 	*used = 0;
 	*tcp_flags = 0;
 	memset(ovs_stats, 0, sizeof(*ovs_stats));
 
-	/* We open code this to make sure node 0 is always considered */
-	for (node = 0; node < MAX_NUMNODES; node = next_node(node, node_possible_map)) {
-		struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[node]);
+	/* We open code this to make sure cpu 0 is always considered */
+	for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) {
+		struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]);
 
 		if (stats) {
 			/* Local CPU may write on non-local stats, so we must
@@ -164,11 +166,11 @@ void ovs_flow_stats_get(const struct sw_flow *flow,
 /* Called with ovs_mutex. */
 void ovs_flow_stats_clear(struct sw_flow *flow)
 {
-	int node;
+	int cpu;
 
-	/* We open code this to make sure node 0 is always considered */
-	for (node = 0; node < MAX_NUMNODES; node = next_node(node, node_possible_map)) {
-		struct flow_stats *stats = ovsl_dereference(flow->stats[node]);
+	/* We open code this to make sure cpu 0 is always considered */
+	for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) {
+		struct flow_stats *stats = ovsl_dereference(flow->stats[cpu]);
 
 		if (stats) {
 			spin_lock_bh(&stats->lock);