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Message-Id: <1471636046-9246-1-git-send-email-cascardo@redhat.com>
Date: Fri, 19 Aug 2016 16:47:26 -0300
From: Thadeu Lima de Souza Cascardo <cascardo@...hat.com>
To: dev@...nvswitch.org
Cc: netdev@...r.kernel.org
Subject: [RFC PATCH] 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.
---
net/openvswitch/flow.c | 39 +++++++++++++++++++++------------------
net/openvswitch/flow.h | 4 ++--
net/openvswitch/flow_table.c | 21 +++++++++++----------
3 files changed, 34 insertions(+), 30 deletions(-)
diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 0ea128e..90ae248 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 = get_cpu();
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;
}
}
@@ -129,6 +131,7 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
stats->tcp_flags |= tcp_flags;
unlock:
spin_unlock(&stats->lock);
+ put_cpu();
}
/* Must be called with rcu_read_lock or ovs_mutex. */
@@ -136,14 +139,14 @@ 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));
- for_each_node(node) {
- struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[node]);
+ for_each_possible_cpu(cpu) {
+ struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]);
if (stats) {
/* Local CPU may write on non-local stats, so we must
@@ -163,10 +166,10 @@ 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;
- for_each_node(node) {
- struct flow_stats *stats = ovsl_dereference(flow->stats[node]);
+ for_each_possible_cpu(cpu) {
+ 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 03378e7..7725ffc 100644
--- a/net/openvswitch/flow.h
+++ b/net/openvswitch/flow.h
@@ -172,14 +172,14 @@ 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 d073fff..6c2ed41 100644
--- 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>
@@ -79,7 +80,7 @@ struct sw_flow *ovs_flow_alloc(void)
{
struct sw_flow *flow;
struct flow_stats *stats;
- int node;
+ int cpu;
flow = kmem_cache_alloc(flow_cache, GFP_KERNEL);
if (!flow)
@@ -89,7 +90,7 @@ struct sw_flow *ovs_flow_alloc(void)
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,
@@ -102,9 +103,9 @@ 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);
+ for_each_possible_cpu(cpu)
+ if (cpu != 0)
+ RCU_INIT_POINTER(flow->stats[cpu], NULL);
return flow;
err:
@@ -142,16 +143,16 @@ 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);
- for_each_node(node)
- if (flow->stats[node])
+ for_each_possible_cpu(cpu)
+ 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);
}
@@ -756,7 +757,7 @@ 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
+ + (num_possible_cpus()
* sizeof(struct flow_stats *)),
0, 0, NULL);
if (flow_cache == NULL)
--
2.7.4
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