Commit db74a333 authored by Thadeu Lima de Souza Cascardo's avatar Thadeu Lima de Souza Cascardo Committed by David S. Miller
Browse files

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: default avatarThadeu Lima de Souza Cascardo <cascardo@redhat.com>
Cc: pravin shelar <pshelar@ovn.org>
Acked-by: default avatarPravin B Shelar <pshelar@ovn.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 40773966

net/openvswitch/flow.c

+22 −20
Original line number Diff line number Diff line
@@ -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);

net/openvswitch/flow.h

+2 −2
Original line number Diff line number Diff line
@@ -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'.

net/openvswitch/flow_table.c

+9 −17
Original line number Diff line number Diff line
@@ -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)

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