[PATCH net-next v1 1/1] net: openvswitch: ovs_packet_cmd_execute put sw_flow mainbody in stack

[Eddy Tao]

Add 2 performance revisions for ovs_packet_cmd_execute

1.Stores mainbody of sw_flow(600+ bytes) in stack
  Benifit: avoid kmem cache alloc/free caused by ovs_flow_alloc/free

2.Define sw_flow_without_stats_init to initialize mainbody of
  struct sw_flow, which does not provides memory for sw_flow_stats.
  Reason: ovs_execute_actions does not touch sw_flow_stats.
  Benefit: less memzero, say each 'sw_flow_stats *' takes 4/8
  bytes, on systems with 20 to 128 logic cpus, this is a good deal.

Signed-off-by: Eddy Tao <taoyuan_eddy@xxxxxxxxxxx>
---
 net/openvswitch/datapath.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index fcee6012293b..337947d34355 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -589,6 +589,12 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 	return err;
 }
 
+static void sw_flow_without_stats_init(struct sw_flow *flow)
+{
+	memset(flow, 0, sizeof(*flow));
+	flow->stats_last_writer = -1;
+}
+
 static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 {
 	struct ovs_header *ovs_header = info->userhdr;
@@ -596,7 +602,8 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 	struct nlattr **a = info->attrs;
 	struct sw_flow_actions *acts;
 	struct sk_buff *packet;
-	struct sw_flow *flow;
+	struct sw_flow f;
+	struct sw_flow *flow = &f;
 	struct sw_flow_actions *sf_acts;
 	struct datapath *dp;
 	struct vport *input_vport;
@@ -636,20 +643,18 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	/* Build an sw_flow for sending this packet. */
-	flow = ovs_flow_alloc();
-	err = PTR_ERR(flow);
-	if (IS_ERR(flow))
-		goto err_kfree_skb;
+	/* This flow has no sw_flow_stats */
+	sw_flow_without_stats_init(flow);
 
 	err = ovs_flow_key_extract_userspace(net, a[OVS_PACKET_ATTR_KEY],
 					     packet, &flow->key, log);
 	if (err)
-		goto err_flow_free;
+		goto err_kfree_skb;
 
 	err = ovs_nla_copy_actions(net, a[OVS_PACKET_ATTR_ACTIONS],
 				   &flow->key, &acts, log);
 	if (err)
-		goto err_flow_free;
+		goto err_kfree_skb;
 
 	rcu_assign_pointer(flow->sf_acts, acts);
 	packet->priority = flow->key.phy.priority;
@@ -677,13 +682,10 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 	local_bh_enable();
 	rcu_read_unlock();
 
-	ovs_flow_free(flow, false);
 	return err;
 
 err_unlock:
 	rcu_read_unlock();
-err_flow_free:
-	ovs_flow_free(flow, false);
 err_kfree_skb:
 	kfree_skb(packet);
 err:
-- 
2.27.0