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net: openvswitch: add flow-mask cache for performance 

The idea of this optimization comes from a patch which
is committed in 2014, openvswitch community. The author
is Pravin B Shelar. In order to get high performance, I
implement it again. Later patches will use it.

Pravin B Shelar, says:
| On every packet OVS needs to lookup flow-table with every
| mask until it finds a match. The packet flow-key is first
| masked with mask in the list and then the masked key is
| looked up in flow-table. Therefore number of masks can
| affect packet processing performance.

Link: 5604935e4e
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Tested-by: Greg Rose <gvrose8192@gmail.com>
Acked-by: William Tu <u9012063@gmail.com>
Signed-off-by: Pravin B Shelar <pshelar@ovn.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tonghao Zhang 2019-11-01 22:23:45 +08:00 committed by David S. Miller
parent ae8a76fb8b
commit 04b7d136d0
3 changed files with 108 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
net/openvswitch/datapath.c
View File

@ -227,7 +227,8 @@ void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)
stats = this_cpu_ptr(dp->stats_percpu);
/* Look up flow. */
flow = ovs_flow_tbl_lookup_stats(&dp->table, key, &n_mask_hit);
flow = ovs_flow_tbl_lookup_stats(&dp->table, key, skb_get_hash(skb),
&n_mask_hit);
if (unlikely(!flow)) {
struct dp_upcall_info upcall;

111
net/openvswitch/flow_table.c
View File

@ -36,6 +36,10 @@
#define TBL_MIN_BUCKETS 1024
#define REHASH_INTERVAL (10 * 60 * HZ)
#define MC_HASH_SHIFT 8
#define MC_HASH_ENTRIES (1u << MC_HASH_SHIFT)
#define MC_HASH_SEGS ((sizeof(uint32_t) * 8) / MC_HASH_SHIFT)
static struct kmem_cache *flow_cache;
struct kmem_cache *flow_stats_cache __read_mostly;
@ -168,11 +172,16 @@ int ovs_flow_tbl_init(struct flow_table *table)
{
struct table_instance *ti, *ufid_ti;
ti = table_instance_alloc(TBL_MIN_BUCKETS);
if (!ti)
table->mask_cache = __alloc_percpu(sizeof(struct mask_cache_entry) *
MC_HASH_ENTRIES,
__alignof__(struct mask_cache_entry));
if (!table->mask_cache)
return -ENOMEM;
ti = table_instance_alloc(TBL_MIN_BUCKETS);
if (!ti)
goto free_mask_cache;
ufid_ti = table_instance_alloc(TBL_MIN_BUCKETS);
if (!ufid_ti)
goto free_ti;
@ -187,6 +196,8 @@ int ovs_flow_tbl_init(struct flow_table *table)
free_ti:
__table_instance_destroy(ti);
free_mask_cache:
free_percpu(table->mask_cache);
return -ENOMEM;
}
@ -243,6 +254,7 @@ void ovs_flow_tbl_destroy(struct flow_table *table)
struct table_instance *ti = rcu_dereference_raw(table->ti);
struct table_instance *ufid_ti = rcu_dereference_raw(table->ufid_ti);
free_percpu(table->mask_cache);
table_instance_destroy(ti, ufid_ti, false);
}
@ -425,7 +437,8 @@ static bool ovs_flow_cmp_unmasked_key(const struct sw_flow *flow,
static struct sw_flow *masked_flow_lookup(struct table_instance *ti,
const struct sw_flow_key *unmasked,
const struct sw_flow_mask *mask)
const struct sw_flow_mask *mask,
u32 *n_mask_hit)
{
struct sw_flow *flow;
struct hlist_head *head;
@ -435,6 +448,8 @@ static struct sw_flow *masked_flow_lookup(struct table_instance *ti,
ovs_flow_mask_key(&masked_key, unmasked, false, mask);
hash = flow_hash(&masked_key, &mask->range);
head = find_bucket(ti, hash);
(*n_mask_hit)++;
hlist_for_each_entry_rcu(flow, head, flow_table.node[ti->node_ver]) {
if (flow->mask == mask && flow->flow_table.hash == hash &&
flow_cmp_masked_key(flow, &masked_key, &mask->range))
@ -443,30 +458,97 @@ static struct sw_flow *masked_flow_lookup(struct table_instance *ti,
return NULL;
}
struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
const struct sw_flow_key *key,
u32 *n_mask_hit)
static struct sw_flow *flow_lookup(struct flow_table *tbl,
struct table_instance *ti,
const struct sw_flow_key *key,
u32 *n_mask_hit)
{
struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
struct sw_flow_mask *mask;
struct sw_flow *flow;
*n_mask_hit = 0;
list_for_each_entry_rcu(mask, &tbl->mask_list, list) {
(*n_mask_hit)++;
flow = masked_flow_lookup(ti, key, mask);
flow = masked_flow_lookup(ti, key, mask, n_mask_hit);
if (flow) /* Found */
return flow;
}
return NULL;
}
/*
* mask_cache maps flow to probable mask. This cache is not tightly
* coupled cache, It means updates to mask list can result in inconsistent
* cache entry in mask cache.
* This is per cpu cache and is divided in MC_HASH_SEGS segments.
* In case of a hash collision the entry is hashed in next segment.
* */
struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *tbl,
const struct sw_flow_key *key,
u32 skb_hash,
u32 *n_mask_hit)
{
struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
struct mask_cache_entry *entries, *ce, *del;
struct sw_flow *flow;
u32 hash = skb_hash;
int seg;
*n_mask_hit = 0;
if (unlikely(!skb_hash))
return flow_lookup(tbl, ti, key, n_mask_hit);
del = NULL;
entries = this_cpu_ptr(tbl->mask_cache);
for (seg = 0; seg < MC_HASH_SEGS; seg++) {
int index;
index = hash & (MC_HASH_ENTRIES - 1);
ce = &entries[index];
if (ce->skb_hash == skb_hash) {
struct sw_flow_mask *mask;
int i;
i = 0;
list_for_each_entry_rcu(mask, &tbl->mask_list, list) {
if (ce->mask_index == i++) {
flow = masked_flow_lookup(ti, key, mask,
n_mask_hit);
if (flow) /* Found */
return flow;
break;
}
}
del = ce;
break;
}
if (!del || (del->skb_hash && !ce->skb_hash)) {
del = ce;
}
hash >>= MC_HASH_SHIFT;
}
flow = flow_lookup(tbl, ti, key, n_mask_hit);
if (flow) {
del->skb_hash = skb_hash;
del->mask_index = (*n_mask_hit - 1);
}
return flow;
}
struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *tbl,
const struct sw_flow_key *key)
{
struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
u32 __always_unused n_mask_hit;
return ovs_flow_tbl_lookup_stats(tbl, key, &n_mask_hit);
return flow_lookup(tbl, ti, key, &n_mask_hit);
}
struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl,
@ -475,10 +557,11 @@ struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl,
struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
struct sw_flow_mask *mask;
struct sw_flow *flow;
u32 __always_unused n_mask_hit;
/* Always called under ovs-mutex. */
list_for_each_entry(mask, &tbl->mask_list, list) {
flow = masked_flow_lookup(ti, match->key, mask);
flow = masked_flow_lookup(ti, match->key, mask, &n_mask_hit);
if (flow && ovs_identifier_is_key(&flow->id) &&
ovs_flow_cmp_unmasked_key(flow, match))
return flow;
@ -631,7 +714,7 @@ static int flow_mask_insert(struct flow_table *tbl, struct sw_flow *flow,
return -ENOMEM;
mask->key = new->key;
mask->range = new->range;
list_add_rcu(&mask->list, &tbl->mask_list);
list_add_tail_rcu(&mask->list, &tbl->mask_list);
} else {
BUG_ON(!mask->ref_count);
mask->ref_count++;

11
net/openvswitch/flow_table.h
View File

@ -22,6 +22,11 @@
#include "flow.h"
struct mask_cache_entry {
u32 skb_hash;
u32 mask_index;
};
struct table_instance {
struct hlist_head *buckets;
unsigned int n_buckets;
@ -34,6 +39,7 @@ struct table_instance {
struct flow_table {
struct table_instance __rcu *ti;
struct table_instance __rcu *ufid_ti;
struct mask_cache_entry __percpu *mask_cache;
struct list_head mask_list;
unsigned long last_rehash;
unsigned int count;
@ -60,8 +66,9 @@ int ovs_flow_tbl_num_masks(const struct flow_table *table);
struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *table,
u32 *bucket, u32 *idx);
struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *,
const struct sw_flow_key *,
u32 *n_mask_hit);
const struct sw_flow_key *,
u32 skb_hash,
u32 *n_mask_hit);
struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *,
const struct sw_flow_key *);
struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl,