Simplify flow mask cache replacement without using expensive atomic
memory access to the mask pointers.
Signed-off-by: Andy Zhou <az...@nicira.com>
---
datapath/flow_table.c | 44 +++++++++++++++++++++-----------------------
1 file changed, 21 insertions(+), 23 deletions(-)
diff --git a/datapath/flow_table.c b/datapath/flow_table.c
index 58a25c7..408730f 100644
--- a/datapath/flow_table.c
+++ b/datapath/flow_table.c
@@ -554,8 +554,9 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table
*tbl,
{
struct mask_array *ma = rcu_dereference_ovsl(tbl->mask_array);
struct table_instance *ti = rcu_dereference_ovsl(tbl->ti);
- struct mask_cache_entry *entries, *ce, *del;
+ struct mask_cache_entry *entries, *ce;
struct sw_flow *flow;
+ struct sw_flow_mask *cache;
u32 hash = skb_hash;
int seg;
@@ -566,42 +567,39 @@ struct sw_flow *ovs_flow_tbl_lookup_stats(struct
flow_table *tbl,
return flow_lookup(tbl, ti, ma, key, n_mask_hit, &mask_index);
}
- del = NULL;
+ ce = NULL;
+ cache = NULL;
entries = this_cpu_ptr(tbl->mask_cache);
+ /* Find the cache entry 'ce' to operate on. */
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;
-
- mask = rcu_dereference_ovsl(ma->masks[ce->mask_index]);
- if (mask) {
- flow = masked_flow_lookup(ti, key, mask,
+ int index = hash & (MC_HASH_ENTRIES - 1);
+ struct mask_cache_entry *e;
+
+ e = &entries[index];
+ if (e->skb_hash == skb_hash) {
+ cache = rcu_dereference_ovsl(ma->masks[e->mask_index]);
+ if (cache) {
+ flow = masked_flow_lookup(ti, key, cache,
n_mask_hit);
- if (flow) /* Found */
+ if (flow) /* Cache hit. */
return flow;
-
}
- del = ce;
+
+ ce = e; /* The best cache replacement candidate. */
break;
}
- if (!del || (del->skb_hash && !ce->skb_hash) ||
- (rcu_dereference_ovsl(ma->masks[del->mask_index]) &&
- !rcu_dereference_ovsl(ma->masks[ce->mask_index]))) {
- del = ce;
- }
+ if (!ce || e->skb_hash > ce->skb_hash)
+ ce = e; /* A better replacement cache candidate. */
hash >>= MC_HASH_SHIFT;
}
- flow = flow_lookup(tbl, ti, ma, key, n_mask_hit, &del->mask_index);
+ /* Cache miss, do full lookup. */
+ flow = flow_lookup(tbl, ti, ma, key, n_mask_hit, &ce->mask_index);
if (flow)
- del->skb_hash = skb_hash;
+ ce->skb_hash = skb_hash;
return flow;
}
--
1.9.1
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