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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: Tonghao Zhang <xiangxia.m.yue@gmail.com> Tested-by: Greg Rose <gvrose8192@gmail.com> Acked-by: Pravin B Shelar <pshelar@ovn.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -518,8 +518,8 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl,
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u32 *n_mask_hit,
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u32 *index)
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{
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struct sw_flow_mask *mask;
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struct sw_flow *flow;
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struct sw_flow_mask *mask;
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int i;
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if (*index < ma->max) {
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@ -538,7 +538,7 @@ static struct sw_flow *flow_lookup(struct flow_table *tbl,
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mask = rcu_dereference_ovsl(ma->masks[i]);
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if (!mask)
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continue;
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break;
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flow = masked_flow_lookup(ti, key, mask, n_mask_hit);
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if (flow) { /* Found */
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@ -695,8 +695,7 @@ struct sw_flow *ovs_flow_tbl_lookup_ufid(struct flow_table *tbl,
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int ovs_flow_tbl_num_masks(const struct flow_table *table)
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{
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struct mask_array *ma = rcu_dereference_ovsl(table->mask_array);
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return ma->count;
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return READ_ONCE(ma->count);
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}
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static struct table_instance *table_instance_expand(struct table_instance *ti,
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@ -705,21 +704,33 @@ static struct table_instance *table_instance_expand(struct table_instance *ti,
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return table_instance_rehash(ti, ti->n_buckets * 2, ufid);
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}
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static void tbl_mask_array_delete_mask(struct mask_array *ma,
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struct sw_flow_mask *mask)
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static void tbl_mask_array_del_mask(struct flow_table *tbl,
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struct sw_flow_mask *mask)
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{
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int i;
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struct mask_array *ma = ovsl_dereference(tbl->mask_array);
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int i, ma_count = READ_ONCE(ma->count);
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/* Remove the deleted mask pointers from the array */
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for (i = 0; i < ma->max; i++) {
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if (mask == ovsl_dereference(ma->masks[i])) {
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RCU_INIT_POINTER(ma->masks[i], NULL);
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ma->count--;
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kfree_rcu(mask, rcu);
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return;
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}
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for (i = 0; i < ma_count; i++) {
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if (mask == ovsl_dereference(ma->masks[i]))
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goto found;
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}
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BUG();
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return;
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found:
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WRITE_ONCE(ma->count, ma_count -1);
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rcu_assign_pointer(ma->masks[i], ma->masks[ma_count -1]);
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RCU_INIT_POINTER(ma->masks[ma_count -1], NULL);
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kfree_rcu(mask, rcu);
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/* Shrink the mask array if necessary. */
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if (ma->max >= (MASK_ARRAY_SIZE_MIN * 2) &&
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ma_count <= (ma->max / 3))
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tbl_mask_array_realloc(tbl, ma->max / 2);
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}
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/* Remove 'mask' from the mask list, if it is not needed any more. */
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@ -733,17 +744,8 @@ static void flow_mask_remove(struct flow_table *tbl, struct sw_flow_mask *mask)
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BUG_ON(!mask->ref_count);
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mask->ref_count--;
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if (!mask->ref_count) {
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struct mask_array *ma;
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ma = ovsl_dereference(tbl->mask_array);
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tbl_mask_array_delete_mask(ma, mask);
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/* Shrink the mask array if necessary. */
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if (ma->max >= (MASK_ARRAY_SIZE_MIN * 2) &&
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ma->count <= (ma->max / 3))
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tbl_mask_array_realloc(tbl, ma->max / 2);
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}
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if (!mask->ref_count)
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tbl_mask_array_del_mask(tbl, mask);
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}
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}
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@ -807,6 +809,29 @@ static struct sw_flow_mask *flow_mask_find(const struct flow_table *tbl,
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return NULL;
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}
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static int tbl_mask_array_add_mask(struct flow_table *tbl,
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struct sw_flow_mask *new)
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{
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struct mask_array *ma = ovsl_dereference(tbl->mask_array);
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int err, ma_count = READ_ONCE(ma->count);
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if (ma_count >= ma->max) {
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err = tbl_mask_array_realloc(tbl, ma->max +
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MASK_ARRAY_SIZE_MIN);
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if (err)
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return err;
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ma = ovsl_dereference(tbl->mask_array);
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}
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BUG_ON(ovsl_dereference(ma->masks[ma_count]));
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rcu_assign_pointer(ma->masks[ma_count], new);
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WRITE_ONCE(ma->count, ma_count +1);
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return 0;
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}
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/* Add 'mask' into the mask list, if it is not already there. */
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static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
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const struct sw_flow_mask *new)
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@ -815,9 +840,6 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
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mask = flow_mask_find(tbl, new);
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if (!mask) {
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struct mask_array *ma;
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int i;
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/* Allocate a new mask if none exsits. */
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mask = mask_alloc();
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if (!mask)
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@ -826,29 +848,9 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
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mask->range = new->range;
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/* Add mask to mask-list. */
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ma = ovsl_dereference(tbl->mask_array);
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if (ma->count >= ma->max) {
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int err;
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err = tbl_mask_array_realloc(tbl, ma->max +
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MASK_ARRAY_SIZE_MIN);
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if (err) {
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kfree(mask);
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return err;
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}
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ma = ovsl_dereference(tbl->mask_array);
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}
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for (i = 0; i < ma->max; i++) {
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const struct sw_flow_mask *t;
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t = ovsl_dereference(ma->masks[i]);
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if (!t) {
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rcu_assign_pointer(ma->masks[i], mask);
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ma->count++;
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break;
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}
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if (tbl_mask_array_add_mask(tbl, mask)) {
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kfree(mask);
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return -ENOMEM;
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}
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} else {
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BUG_ON(!mask->ref_count);
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