Date:   Fri, 27 Jul 2018 16:03:57 +0800
From:   Li RongQing <lirongqing@...du.com>
To:     netdev@...r.kernel.org, pshelar@....org
Subject: [PATCH][net-next] openvswitch: eliminate cpu_used_mask from sw_flow

The size of struct cpumask varies with CONFIG_NR_CPUS, some config
CONFIG_NR_CPUS is very larger, like 5120, struct cpumask will take
640 bytes, if there is thousands of flows, it will take lots of
memory

cpu_used_mask has two purposes
1: Assume first cpu as cpu0 which maybe not true; now use
   cpumask_first(cpu_possible_mask)
2: when get/clear statistic, reduce the iteratation; but it
   is not hot path, so use for_each_possible_cpu

Signed-off-by: Zhang Yu <zhangyu31@...du.com>
Signed-off-by: Li RongQing <lirongqing@...du.com>
---
 net/openvswitch/flow.c       | 11 +++++------
 net/openvswitch/flow.h       |  5 ++---
 net/openvswitch/flow_table.c | 11 +++++------
 3 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 56b8e7167790..ad580bec00fb 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -85,7 +85,9 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 		if (cpu == 0 && unlikely(flow->stats_last_writer != cpu))
 			flow->stats_last_writer = cpu;
 	} else {
-		stats = rcu_dereference(flow->stats[0]); /* Pre-allocated. */
+		int cpu1 = cpumask_first(cpu_possible_mask);
+
+		stats = rcu_dereference(flow->stats[cpu1]); /* Pre-allocated. */
 		spin_lock(&stats->lock);
 
 		/* If the current CPU is the only writer on the
@@ -118,7 +120,6 @@ void ovs_flow_stats_update(struct sw_flow *flow, __be16 tcp_flags,
 
 					rcu_assign_pointer(flow->stats[cpu],
 							   new_stats);
-					cpumask_set_cpu(cpu, &flow->cpu_used_mask);
 					goto unlock;
 				}
 			}
@@ -145,8 +146,7 @@ void ovs_flow_stats_get(const struct sw_flow *flow,
 	*tcp_flags = 0;
 	memset(ovs_stats, 0, sizeof(*ovs_stats));
 
-	/* We open code this to make sure cpu 0 is always considered */
-	for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask)) {
+	for_each_possible_cpu(cpu) {
 		struct flow_stats *stats = rcu_dereference_ovsl(flow->stats[cpu]);
 
 		if (stats) {
@@ -169,8 +169,7 @@ void ovs_flow_stats_clear(struct sw_flow *flow)
 {
 	int cpu;
 
-	/* We open code this to make sure cpu 0 is always considered */
-	for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask)) {
+	for_each_possible_cpu(cpu) {
 		struct flow_stats *stats = ovsl_dereference(flow->stats[cpu]);
 
 		if (stats) {
diff --git a/net/openvswitch/flow.h b/net/openvswitch/flow.h
index c670dd24b8b7..d0ea5d6ced3e 100644
--- a/net/openvswitch/flow.h
+++ b/net/openvswitch/flow.h
@@ -223,17 +223,16 @@ struct sw_flow {
 		u32 hash;
 	} flow_table, ufid_table;
 	int stats_last_writer;		/* CPU id of the last writer on
-					 * 'stats[0]'.
+					 * 'stats[first cpu id]'.
 					 */
 	struct sw_flow_key key;
 	struct sw_flow_id id;
-	struct cpumask cpu_used_mask;
 	struct sw_flow_mask *mask;
 	struct sw_flow_actions __rcu *sf_acts;
 	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'.
+					   * while holding the 'stats[first cpu id].lock'
 					   */
 };
 
diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 80ea2a71852e..e4dbd65c308a 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -80,6 +80,7 @@ struct sw_flow *ovs_flow_alloc(void)
 {
 	struct sw_flow *flow;
 	struct flow_stats *stats;
+	int cpu = cpumask_first(cpu_possible_mask);
 
 	flow = kmem_cache_zalloc(flow_cache, GFP_KERNEL);
 	if (!flow)
@@ -90,15 +91,13 @@ struct sw_flow *ovs_flow_alloc(void)
 	/* Initialize the default stat node. */
 	stats = kmem_cache_alloc_node(flow_stats_cache,
 				      GFP_KERNEL | __GFP_ZERO,
-				      node_online(0) ? 0 : NUMA_NO_NODE);
+				      cpu_to_node(cpu));
 	if (!stats)
 		goto err;
 
 	spin_lock_init(&stats->lock);
 
-	RCU_INIT_POINTER(flow->stats[0], stats);
-
-	cpumask_set_cpu(0, &flow->cpu_used_mask);
+	RCU_INIT_POINTER(flow->stats[cpu], stats);
 
 	return flow;
 err:
@@ -142,11 +141,11 @@ static void flow_free(struct sw_flow *flow)
 		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 cpu 0 is always considered */
-	for (cpu = 0; cpu < nr_cpu_ids; cpu = cpumask_next(cpu, &flow->cpu_used_mask))
+	for_each_possible_cpu(cpu) {
 		if (flow->stats[cpu])
 			kmem_cache_free(flow_stats_cache,
 					(struct flow_stats __force *)flow->stats[cpu]);
+	}
 	kmem_cache_free(flow_cache, flow);
 }
 
-- 
2.16.2

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