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openvswitch: use percpu flow stats

Browse source 
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>
This commit is contained in:
Thadeu Lima de Souza Cascardo 2016-09-15 19:11:53 -03:00 • committed by David S. Miller
parent 40773966cc
commit db74a3335e
3 changed files with 33 additions and 39 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

42
net/openvswitch/flow.c
View file

@ -29,6 +29,7 @@
#include <linux/module.h> #include <linux/module.h>
#include <linux/in.h> #include <linux/in.h>
#include <linux/rcupdate.h> #include <linux/rcupdate.h>
#include <linux/cpumask.h>
#include <linux/if_arp.h> #include <linux/if_arp.h>
#include <linux/ip.h> #include <linux/ip.h>
#include <linux/ipv6.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; struct flow_stats *stats;
int node = numa_node_id(); int node = numa_node_id();
int cpu = smp_processor_id();
int len = skb->len + (skb_vlan_tag_present(skb) ? VLAN_HLEN : 0); 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)) { if (likely(stats)) {
spin_lock(&stats->lock); spin_lock(&stats->lock);
/* Mark if we write on the pre-allocated stats. */ /* Mark if we write on the pre-allocated stats. */
if (node == 0 && unlikely(flow->stats_last_writer != node)) if (cpu == 0 && unlikely(flow->stats_last_writer != cpu))
flow->stats_last_writer = node; flow->stats_last_writer = cpu;
} else { } else {
stats = rcu_dereference(flow->stats[0]); /* Pre-allocated. */ stats = rcu_dereference(flow->stats[0]); /* Pre-allocated. */
spin_lock(&stats->lock); 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. * 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 /* 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- * stats were already allocated, we update the pre-
* allocated stats as we have already locked them. * allocated stats as we have already locked them.
*/ */
if (likely(flow->stats_last_writer != NUMA_NO_NODE) if (likely(flow->stats_last_writer != -1) &&
&& likely(!rcu_access_pointer(flow->stats[node]))) { likely(!rcu_access_pointer(flow->stats[cpu]))) {
/* Try to allocate node-specific stats. */ /* Try to allocate CPU-specific stats. */
struct flow_stats *new_stats; struct flow_stats *new_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; new_stats->tcp_flags = tcp_flags;
spin_lock_init(&new_stats->lock); spin_lock_init(&new_stats->lock);
rcu_assign_pointer(flow->stats[node], rcu_assign_pointer(flow->stats[cpu],
new_stats); new_stats);
goto unlock; 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, struct ovs_flow_stats *ovs_stats,
unsigned long *used, __be16 *tcp_flags) unsigned long *used, __be16 *tcp_flags)
{ {
int node; int cpu;
*used = 0; *used = 0;
*tcp_flags = 0; *tcp_flags = 0;
memset(ovs_stats, 0, sizeof(*ovs_stats)); memset(ovs_stats, 0, sizeof(*ovs_stats));
/* We open code this to make sure node 0 is always considered */ /* We open code this to make sure cpu 0 is always considered */
for (node = 0; node < MAX_NUMNODES; node = next_node(node, node_possible_map)) { for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) {
struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[node]); struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]);
if (stats) { if (stats) {
/* Local CPU may write on non-local stats, so we must /* 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. */ /* Called with ovs_mutex. */
void ovs_flow_stats_clear(struct sw_flow *flow) 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 */ /* We open code this to make sure cpu 0 is always considered */
for (node = 0; node < MAX_NUMNODES; node = next_node(node, node_possible_map)) { for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask)) {
struct flow_stats *stats = ovsl_dereference(flow->stats[node]); struct flow_stats *stats = ovsl_dereference(flow->stats[cpu]);
if (stats) { if (stats) {
spin_lock_bh(&stats->lock); spin_lock_bh(&stats->lock);

4
net/openvswitch/flow.h
View file

@ -178,14 +178,14 @@ struct sw_flow {
struct hlist_node node[2]; struct hlist_node node[2];
u32 hash; u32 hash;
} flow_table, ufid_table; } 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]'. * 'stats[0]'.
*/ */
struct sw_flow_key key; struct sw_flow_key key;
struct sw_flow_id id; struct sw_flow_id id;
struct sw_flow_mask *mask; struct sw_flow_mask *mask;
struct sw_flow_actions __rcu *sf_acts; 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, * is allocated at flow creation time,
* the rest are allocated on demand * the rest are allocated on demand
* while holding the 'stats[0].lock'. * while holding the 'stats[0].lock'.

26
net/openvswitch/flow_table.c
View file

@ -32,6 +32,7 @@
#include <linux/module.h> #include <linux/module.h>
#include <linux/in.h> #include <linux/in.h>
#include <linux/rcupdate.h> #include <linux/rcupdate.h>
#include <linux/cpumask.h>
#include <linux/if_arp.h> #include <linux/if_arp.h>
#include <linux/ip.h> #include <linux/ip.h>
#include <linux/ipv6.h> #include <linux/ipv6.h>
@ -79,17 +80,12 @@ struct sw_flow *ovs_flow_alloc(void)
{ {
struct sw_flow *flow; struct sw_flow *flow;
struct flow_stats *stats; struct flow_stats *stats;
int node;
flow = kmem_cache_alloc(flow_cache, GFP_KERNEL); flow = kmem_cache_zalloc(flow_cache, GFP_KERNEL);
if (!flow) if (!flow)
return ERR_PTR(-ENOMEM); return ERR_PTR(-ENOMEM);
flow->sf_acts = NULL; flow->stats_last_writer = -1;
flow->mask = NULL;
flow->id.unmasked_key = NULL;
flow->id.ufid_len = 0;
flow->stats_last_writer = NUMA_NO_NODE;
/* Initialize the default stat node. */ /* Initialize the default stat node. */
stats = kmem_cache_alloc_node(flow_stats_cache, 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); RCU_INIT_POINTER(flow->stats[0], stats);
for_each_node(node)
if (node != 0)
RCU_INIT_POINTER(flow->stats[node], NULL);
return flow; return flow;
err: err:
kmem_cache_free(flow_cache, flow); 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) static void flow_free(struct sw_flow *flow)
{ {
int node; int cpu;
if (ovs_identifier_is_key(&flow->id)) if (ovs_identifier_is_key(&flow->id))
kfree(flow->id.unmasked_key); kfree(flow->id.unmasked_key);
if (flow->sf_acts) if (flow->sf_acts)
ovs_nla_free_flow_actions((struct sw_flow_actions __force *)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 */ /* We open code this to make sure cpu 0 is always considered */
for (node = 0; node < MAX_NUMNODES; node = next_node(node, node_possible_map)) for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, cpu_possible_mask))
if (node != 0 && flow->stats[node]) if (flow->stats[cpu])
kmem_cache_free(flow_stats_cache, 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); 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)); BUILD_BUG_ON(sizeof(struct sw_flow_key) % sizeof(long));
flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow) flow_cache = kmem_cache_create("sw_flow", sizeof(struct sw_flow)
+ (nr_node_ids + (nr_cpu_ids
* sizeof(struct flow_stats *)), * sizeof(struct flow_stats *)),
0, 0, NULL); 0, 0, NULL);
if (flow_cache == NULL) if (flow_cache == NULL)