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>

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 5b80612..0fa4543 100644 (file)
--- 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);

diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h
index 156a302..ae783f5 100644 (file)
--- a/net/openvswitch/flow.h
+++ b/net/openvswitch/flow.h
@@ -178,14 +178,14 @@ struct sw_flow {
                struct hlist_node node[2];
                u32 hash;
        } flow_table, ufid_table;
-       int stats_last_writer;          /* NUMA-node id of the last writer on
+       int stats_last_writer;          /* CPU id of the last writer on
                                         * 'stats[0]'.
                                         */
        struct sw_flow_key key;
        struct sw_flow_id id;
        struct sw_flow_mask *mask;
        struct sw_flow_actions __rcu *sf_acts;
-       struct flow_stats __rcu *stats[]; /* One for each NUMA node.  First one
+       struct flow_stats __rcu *stats[]; /* One for each CPU.  First one
                                           * is allocated at flow creation time,
                                           * the rest are allocated on demand
                                           * while holding the 'stats[0].lock'.

diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 957a3c3..ea7a807 100644 (file)
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -32,6 +32,7 @@
 #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>
@@ -79,17 +80,12 @@ struct sw_flow *ovs_flow_alloc(void)
 {
        struct sw_flow *flow;
        struct flow_stats *stats;
-       int node;
 
-       flow = kmem_cache_alloc(flow_cache, GFP_KERNEL);
+       flow = kmem_cache_zalloc(flow_cache, GFP_KERNEL);
        if (!flow)
                return ERR_PTR(-ENOMEM);
 
-       flow->sf_acts = NULL;
-       flow->mask = NULL;
-       flow->id.unmasked_key = NULL;
-       flow->id.ufid_len = 0;
-       flow->stats_last_writer = NUMA_NO_NODE;
+       flow->stats_last_writer = -1;
 
        /* Initialize the default stat node. */
        stats = kmem_cache_alloc_node(flow_stats_cache,
@@ -102,10 +98,6 @@ struct sw_flow *ovs_flow_alloc(void)
 
        RCU_INIT_POINTER(flow->stats[0], stats);
 
-       for_each_node(node)
-               if (node != 0)
-                       RCU_INIT_POINTER(flow->stats[node], NULL);
-
        return flow;
 err:
        kmem_cache_free(flow_cache, flow);
@@ -142,17 +134,17 @@ static struct flex_array *alloc_buckets(unsigned int n_buckets)
 
 static void flow_free(struct sw_flow *flow)
 {
-       int node;
+       int cpu;
 
        if (ovs_identifier_is_key(&flow->id))
                kfree(flow->id.unmasked_key);
        if (flow->sf_acts)
                ovs_nla_free_flow_actions((struct sw_flow_actions __force *)flow->sf_acts);
-       /* 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))
-               if (node != 0 && 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))
+               if (flow->stats[cpu])
                        kmem_cache_free(flow_stats_cache,
-                                       (struct flow_stats __force *)flow->stats[node]);
+                                       (struct flow_stats __force *)flow->stats[cpu]);
        kmem_cache_free(flow_cache, flow);
 }
 
@@ -757,7 +749,7 @@ int ovs_flow_init(void)
        BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long));
 
        flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow)
-                                      + (nr_node_ids
+                                      + (nr_cpu_ids
                                          * sizeof(struct flow_stats *)),
                                       0, 0, NULL);
        if (flow_cache == NULL)