From: Ben Pfaff <blp@nicira.com>
Date: Mon, 16 Mar 2009 18:37:34 +0000 (-0700)
Subject: datapath: Speed up ioctl fast paths.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=876d3efc253cb6507ef47c2fa0f267a11722d8a9;p=openvswitch

datapath: Speed up ioctl fast paths.

synchronize_rcu() was causing some common datapath ioctls to take up to
approx. 1 second (!) in some cases, which was killing our performance.
Use call_rcu() instead.
---

diff --git a/datapath/datapath.c b/datapath/datapath.c
index e636c8ad..8b26d5a0 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -794,8 +794,7 @@ static int set_flow_actions(struct datapath *dp, struct odp_flow __user *ufp)
 		goto error_free_actions;
 	old_acts = rcu_dereference(flow->sf_acts);
 	rcu_assign_pointer(flow->sf_acts, new_acts);
-	synchronize_rcu();	/* XXX expensive! */
-	kfree(old_acts);
+	flow_deferred_free_acts(old_acts);
 
 	return 0;
 
@@ -883,9 +882,13 @@ static int add_flow(struct datapath *dp, struct odp_flow __user *ufp)
 		/* Replace 'old_flow' by 'flow'. */
 		struct sw_flow *old_flow = *rcu_dereference(bucket);
 		rcu_assign_pointer(*bucket, flow);
-		synchronize_rcu();	/* XXX expensive! */
+
+		/* XXX These statistics might lose a few packets, since other
+		 * CPUs can be using this flow.  We used to synchronize_rcu()
+		 * to make sure that we get completely accurate stats, but that
+		 * blows our performance, badly. */
 		error = put_stats(old_flow, ufp) ? -EFAULT : 0;
-		flow_free(old_flow);
+		flow_deferred_free(old_flow);
 	}
 
 	return error;
@@ -951,10 +954,14 @@ static int del_or_query_flow(struct datapath *dp,
 		error = dp_table_delete(table, flow);
 		if (error)
 			goto error;
+
+		/* XXX These statistics might lose a few packets, since other
+		 * CPUs can be using this flow.  We used to synchronize_rcu()
+		 * to make sure that we get completely accurate stats, but that
+		 * blows our performance, badly. */
 		dp->n_flows--;
-		synchronize_rcu();	/* XXX expensive! */
 		error = answer_query(flow, ufp);
-		flow_free(flow);
+		flow_deferred_free(flow);
 	} else {
 		error = answer_query(flow, ufp);
 	}