Commit 57f7d7b9 authored by Tonghao Zhang's avatar Tonghao Zhang Committed by David S. Miller
Browse files

net: openvswitch: optimize flow-mask looking up 



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.

One bad case, for example: M means flow-mask is valid and NULL
of flow-mask means deleted.

+-------------------------------------------+
| M | NULL | ...                  | NULL | M|
+-------------------------------------------+

In that case, without this patch, openvswitch will traverses all
mask array, because there will be one flow-mask in the tail. This
patch changes the way of flow-mask inserting and deleting, and the
mask array will be keep as below: there is not a NULL hole. In the
fast path, we can "break" "for" (not "continue") in flow_lookup
when we get a NULL flow-mask.

         "break"
            v
+-------------------------------------------+
| M | M |  NULL |...           | NULL | NULL|
+-------------------------------------------+

This patch don't optimize slow or control path, still using ma->max
to traverse. Slow path:
* tbl_mask_array_realloc
* ovs_flow_tbl_lookup_exact
* flow_mask_find

Signed-off-by: default avatarTonghao Zhang <xiangxia.m.yue@gmail.com>
Tested-by: default avatarGreg Rose <gvrose8192@gmail.com>
Acked-by: default avatarPravin B Shelar <pshelar@ovn.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a7f35e78

net/openvswitch/flow_table.c

+53 −51
Original line number Diff line number Diff line
@@ -518,8 +518,8 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl, 
				   u32 *n_mask_hit,

				   u32 *index)

{

	struct sw_flow_mask *mask;

	struct sw_flow *flow;

	struct sw_flow_mask *mask;

	int i;



	if (*index < ma->max) {
@@ -538,7 +538,7 @@ 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 */
@@ -695,8 +695,7 @@ struct sw_flow *ovs_flow_tbl_lookup_ufid(struct flow_table *tbl, 
int ovs_flow_tbl_num_masks(const struct flow_table *table)

{

	struct mask_array *ma = rcu_dereference_ovsl(table->mask_array);



	return ma->count;

	return READ_ONCE(ma->count);

}



static struct table_instance *table_instance_expand(struct table_instance *ti,
@@ -705,21 +704,33 @@ 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,

static void tbl_mask_array_del_mask(struct flow_table *tbl,

				    struct sw_flow_mask *mask)

{

	int i;

	struct mask_array *ma = ovsl_dereference(tbl->mask_array);

	int i, ma_count = READ_ONCE(ma->count);



	/* 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:

	WRITE_ONCE(ma->count, ma_count -1);



	rcu_assign_pointer(ma->masks[i], ma->masks[ma_count -1]);

	RCU_INIT_POINTER(ma->masks[ma_count -1], 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. */
@@ -733,17 +744,8 @@ 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);

	}

}
@@ -807,6 +809,29 @@ static struct sw_flow_mask *flow_mask_find(const struct flow_table *tbl, 
	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, ma_count = READ_ONCE(ma->count);



	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);

	WRITE_ONCE(ma->count, ma_count +1);



	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)
@@ -815,9 +840,6 @@ 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)
@@ -826,29 +848,9 @@ 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) {

		if (tbl_mask_array_add_mask(tbl, mask)) {

			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;

			}

			return -ENOMEM;

		}

	} else {

		BUG_ON(!mask->ref_count);

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