[ovs-dev] [PATCH net-next v3 05/10] net: openvswitch: optimize flow-mask looking up

xiangxia.m.yue at gmail.com xiangxia.m.yue at gmail.com
Fri Oct 11 14:00:42 UTC 2019


From: Tonghao Zhang <xiangxia.m.yue at gmail.com>

The full looking up on flow table traverses all mask array.
If mask-array is too large, the number of invalid flow-mask
increase, performance will be drop.

This patch optimizes mask-array operation:

* Inserting, insert it [ma->count- 1] directly.
* Removing, only change last and current mask point, and free current mask.
* Looking up, full looking up will break if mask is NULL.

The function which changes or gets *count* of struct mask_array,
is protected by ovs_lock, but flow_lookup (not protected) should use *max* of
struct mask_array.

Functions protected by ovs_lock:
* tbl_mask_array_del_mask
* tbl_mask_array_add_mask
* flow_mask_find
* ovs_flow_tbl_lookup_exact
* ovs_flow_tbl_num_masks

Signed-off-by: Tonghao Zhang <xiangxia.m.yue at gmail.com>
---
 net/openvswitch/flow_table.c | 114 ++++++++++++++++++++++---------------------
 1 file changed, 58 insertions(+), 56 deletions(-)

diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c
index 4c82960..1b99f8e 100644
--- a/net/openvswitch/flow_table.c
+++ b/net/openvswitch/flow_table.c
@@ -198,10 +198,8 @@ static int tbl_mask_array_realloc(struct flow_table *tbl, int size)
 	if (old) {
 		int i;
 
-		for (i = 0; i < old->max; i++) {
-			if (ovsl_dereference(old->masks[i]))
-				new->masks[new->count++] = old->masks[i];
-		}
+		for (i = 0; i < old->count; i++)
+			new->masks[new->count++] = old->masks[i];
 	}
 
 	rcu_assign_pointer(tbl->mask_array, new);
@@ -538,7 +536,7 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl,
 
 		mask = rcu_dereference_ovsl(ma->masks[i]);
 		if (!mask)
-			continue;
+			break;
 
 		flow = masked_flow_lookup(ti, key, mask, n_mask_hit);
 		if (flow) { /* Found */
@@ -632,15 +630,13 @@ struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl,
 	int i;
 
 	/* Always called under ovs-mutex. */
-	for (i = 0; i < ma->max; i++) {
+	for (i = 0; i < ma->count; i++) {
 		struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
 		u32 __always_unused n_mask_hit;
 		struct sw_flow_mask *mask;
 		struct sw_flow *flow;
 
 		mask = ovsl_dereference(ma->masks[i]);
-		if (!mask)
-			continue;
 
 		flow = masked_flow_lookup(ti, match->key, mask, &n_mask_hit);
 		if (flow && ovs_identifier_is_key(&flow->id) &&
@@ -704,21 +700,34 @@ static struct table_instance *table_instance_expand(struct table_instance *ti,
 	return table_instance_rehash(ti, ti->n_buckets * 2, ufid);
 }
 
-static void tbl_mask_array_delete_mask(struct mask_array *ma,
-				       struct sw_flow_mask *mask)
+static void tbl_mask_array_del_mask(struct flow_table *tbl,
+				    struct sw_flow_mask *mask)
 {
+	struct mask_array *ma = ovsl_dereference(tbl->mask_array);
 	int i;
 
 	/* Remove the deleted mask pointers from the array */
-	for (i = 0; i < ma->max; i++) {
-		if (mask == ovsl_dereference(ma->masks[i])) {
-			RCU_INIT_POINTER(ma->masks[i], NULL);
-			ma->count--;
-			kfree_rcu(mask, rcu);
-			return;
-		}
+	for (i = 0; i < ma->count; i++) {
+		if (mask == ovsl_dereference(ma->masks[i]))
+			goto found;
 	}
+
 	BUG();
+	return;
+
+found:
+	ma->count--;
+	smp_wmb();
+
+	rcu_assign_pointer(ma->masks[i], ma->masks[ma->count]);
+	RCU_INIT_POINTER(ma->masks[ma->count], NULL);
+
+	kfree_rcu(mask, rcu);
+
+	/* Shrink the mask array if necessary. */
+	if (ma->max >= (MASK_ARRAY_SIZE_MIN * 2) &&
+	    ma->count <= (ma->max / 3))
+		tbl_mask_array_realloc(tbl, ma->max / 2);
 }
 
 /* Remove 'mask' from the mask list, if it is not needed any more. */
@@ -732,17 +741,8 @@ static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
 		BUG_ON(!mask->ref_count);
 		mask->ref_count--;
 
-		if (!mask->ref_count) {
-			struct mask_array *ma;
-
-			ma = ovsl_dereference(tbl->mask_array);
-			tbl_mask_array_delete_mask(ma, mask);
-
-			/* Shrink the mask array if necessary. */
-			if (ma->max >= (MASK_ARRAY_SIZE_MIN * 2) &&
-			    ma->count <= (ma->max / 3))
-				tbl_mask_array_realloc(tbl, ma->max / 2);
-		}
+		if (!mask->ref_count)
+			tbl_mask_array_del_mask(tbl, mask);
 	}
 }
 
@@ -795,17 +795,42 @@ static struct sw_flow_mask *flow_mask_find(const struct flow_table *tbl,
 	int i;
 
 	ma = ovsl_dereference(tbl->mask_array);
-	for (i = 0; i < ma->max; i++) {
+	for (i = 0; i < ma->count; i++) {
 		struct sw_flow_mask *t;
 		t = ovsl_dereference(ma->masks[i]);
 
-		if (t && mask_equal(mask, t))
+		if (mask_equal(mask, t))
 			return t;
 	}
 
 	return NULL;
 }
 
+static int tbl_mask_array_add_mask(struct flow_table *tbl,
+				   struct sw_flow_mask *new)
+{
+	struct mask_array *ma = ovsl_dereference(tbl->mask_array);
+	int err;
+
+	if (ma->count >= ma->max) {
+		err = tbl_mask_array_realloc(tbl, ma->max +
+					      MASK_ARRAY_SIZE_MIN);
+		if (err)
+			return err;
+
+		ma = ovsl_dereference(tbl->mask_array);
+	}
+
+	BUG_ON(ovsl_dereference(ma->masks[ma->count]));
+
+	rcu_assign_pointer(ma->masks[ma->count], new);
+
+	smp_wmb();
+	ma->count++;
+
+	return 0;
+}
+
 /* Add 'mask' into the mask list, if it is not already there. */
 static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
 			    const struct sw_flow_mask *new)
@@ -814,9 +839,6 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
 
 	mask = flow_mask_find(tbl, new);
 	if (!mask) {
-		struct mask_array *ma;
-		int i;
-
 		/* Allocate a new mask if none exsits. */
 		mask = mask_alloc();
 		if (!mask)
@@ -825,29 +847,9 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
 		mask->range = new->range;
 
 		/* Add mask to mask-list. */
-		ma = ovsl_dereference(tbl->mask_array);
-		if (ma->count >= ma->max) {
-			int err;
-
-			err = tbl_mask_array_realloc(tbl, ma->max +
-						     MASK_ARRAY_SIZE_MIN);
-			if (err) {
-				kfree(mask);
-				return err;
-			}
-
-			ma = ovsl_dereference(tbl->mask_array);
-		}
-
-		for (i = 0; i < ma->max; i++) {
-			const struct sw_flow_mask *t;
-
-			t = ovsl_dereference(ma->masks[i]);
-			if (!t) {
-				rcu_assign_pointer(ma->masks[i], mask);
-				ma->count++;
-				break;
-			}
+		if (tbl_mask_array_add_mask(tbl, mask)) {
+			kfree(mask);
+			return -ENOMEM;
 		}
 	} else {
 		BUG_ON(!mask->ref_count);
-- 
1.8.3.1



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