From 57f7d7b9164426c496300d254fd5167fbbf205ea Mon Sep 17 00:00:00 2001 From: Tonghao Zhang Date: Fri, 1 Nov 2019 22:23:49 +0800 Subject: [PATCH] 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 Tested-by: Greg Rose Acked-by: Pravin B Shelar Signed-off-by: David S. Miller --- net/openvswitch/flow_table.c | 104 ++++++++++++++++++----------------- 1 file changed, 53 insertions(+), 51 deletions(-) diff --git a/net/openvswitch/flow_table.c b/net/openvswitch/flow_table.c index c7ba43524c2a..a10d421773f8 100644 --- a/net/openvswitch/flow_table.c +++ b/net/openvswitch/flow_table.c @@ -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, - struct sw_flow_mask *mask) +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) { - 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); -- 2.20.1