We have a controller that puts many rules with different reg0 values into
the flow table, where reg0 is used (by "resubmit"s) to distinguish stages
in a pipeline. Thus, any given flow only needs to be hashed into
classifier "cls_table"s that contain a match for the flow's reg0 value.
This commit optimizes the classifier lookup by (probabilistically) skipping
the "cls_table"s that can't possibly match.
This speeds up flow setup performance with the controller in question by
about 19%.
Bug #14282.
Signed-off-by: Ben Pfaff <b...@nicira.com>
---
lib/classifier.c | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++---
lib/classifier.h | 72 +++++++++++++++++++++++++++++++++++---
lib/flow.h | 27 ++++++++++++++-
lib/tag.h | 8 ++++-
4 files changed, 194 insertions(+), 13 deletions(-)
diff --git a/lib/classifier.c b/lib/classifier.c
index d1fe524..8dc0fdc 100644
--- a/lib/classifier.c
+++ b/lib/classifier.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2009, 2010, 2011, 2012 Nicira, Inc.
+ * Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -135,6 +135,7 @@ classifier_init(struct classifier *cls)
{
cls->n_rules = 0;
hmap_init(&cls->tables);
+ hmap_init(&cls->partitions);
}
/* Destroys 'cls'. Rules within 'cls', if any, are not freed; this is the
@@ -143,12 +144,20 @@ void
classifier_destroy(struct classifier *cls)
{
if (cls) {
+ struct cls_table *partition, *next_partition;
struct cls_table *table, *next_table;
HMAP_FOR_EACH_SAFE (table, next_table, hmap_node, &cls->tables) {
destroy_table(cls, table);
}
hmap_destroy(&cls->tables);
+
+ HMAP_FOR_EACH_SAFE (partition, next_partition, hmap_node,
+ &cls->partitions) {
+ hmap_remove(&cls->partitions, &partition->hmap_node);
+ free(partition);
+ }
+ hmap_destroy(&cls->partitions);
}
}
@@ -166,6 +175,39 @@ classifier_count(const struct classifier *cls)
return cls->n_rules;
}
+static struct cls_partition *
+find_partition(const struct classifier *cls, uint32_t reg0, uint32_t hash)
+{
+ struct cls_partition *partition;
+
+ HMAP_FOR_EACH_IN_BUCKET (partition, hmap_node, hash, &cls->partitions) {
+ if (partition->reg0 == reg0) {
+ return partition;
+ }
+ }
+
+ return NULL;
+}
+
+static struct cls_partition *
+create_partition(struct classifier *cls, struct cls_table *table,
+ uint32_t reg0)
+{
+ uint32_t hash = hash_int(reg0, 0);
+ struct cls_partition *partition = find_partition(cls, reg0, hash);
+ if (partition) {
+ partition->n_refs++;
+ partition->tags |= table->tag;
+ } else {
+ partition = xmalloc(sizeof *partition);
+ partition->n_refs = 1;
+ partition->tags = table->tag;
+ partition->reg0 = reg0;
+ hmap_insert(&cls->partitions, &partition->hmap_node, hash);
+ }
+ return partition;
+}
+
/* Inserts 'rule' into 'cls'. Until 'rule' is removed from 'cls', the caller
* must not modify or free it.
*
@@ -192,8 +234,17 @@ classifier_replace(struct classifier *cls, struct cls_rule
*rule)
old_rule = insert_rule(table, rule);
if (!old_rule) {
+ if (minimask_get_reg_mask(&rule->match.mask, 0) == UINT32_MAX) {
+ uint32_t reg0 = miniflow_get_reg(&rule->match.flow, 0);
+ rule->partition = create_partition(cls, table, reg0);
+ } else {
+ rule->partition = NULL;
+ }
+
table->n_table_rules++;
cls->n_rules++;
+ } else {
+ rule->partition = old_rule->partition;
}
return old_rule;
}
@@ -217,6 +268,7 @@ classifier_insert(struct classifier *cls, struct cls_rule
*rule)
void
classifier_remove(struct classifier *cls, struct cls_rule *rule)
{
+ struct cls_partition *partition;
struct cls_rule *head;
struct cls_table *table;
@@ -234,6 +286,12 @@ classifier_remove(struct classifier *cls, struct cls_rule
*rule)
hmap_replace(&table->rules, &rule->hmap_node, &next->hmap_node);
}
+ partition = rule->partition;
+ if (partition && --partition->n_refs == 0) {
+ hmap_remove(&cls->partitions, &partition->hmap_node);
+ free(partition);
+ }
+
if (--table->n_table_rules == 0) {
destroy_table(cls, table);
}
@@ -247,14 +305,41 @@ classifier_remove(struct classifier *cls, struct cls_rule
*rule)
struct cls_rule *
classifier_lookup(const struct classifier *cls, const struct flow *flow)
{
+ const struct cls_partition *partition;
struct cls_table *table;
struct cls_rule *best;
+ tag_type tags;
+
+ /* Determine 'tags' such that, if 'table->tag' doesn't intersect them, then
+ * 'flow' cannot possibly match in 'table':
+ *
+ * - If flow->regs[0] maps to a given 'partition', then we can use
+ * 'tags' for 'partition->tags'.
+ *
+ * - If flow->regs[0] has no partition, then no rule in 'cls' has an
+ * exact-match for flow->regs[0]. That means that we don't need to
+ * search any table that includes flow->regs[0] in its mask.
+ *
+ * In either case, we always need to search any cls_tables that do not
+ * include flow->regs[0] in its mask. One way to do that would be to check
+ * the "cls_table"s explicitly for that, but that would require an extra
+ * branch per table. Instead, we mark such a cls_table's 'tags' as TAG_ALL
+ * and make sure that 'tags' is never empty. This means that 'tags' always
+ * intersects such a cls_table's 'tags', so we don't need a special case.
+ */
+ partition = (hmap_is_empty(&cls->partitions)
+ ? NULL
+ : find_partition(cls, flow->regs[0],
+ hash_int(flow->regs[0], 0)));
+ tags = partition ? partition->tags : TAG_ARBITRARY;
best = NULL;
HMAP_FOR_EACH (table, hmap_node, &cls->tables) {
- struct cls_rule *rule = find_match(table, flow);
- if (rule && (!best || rule->priority > best->priority)) {
- best = rule;
+ if (tag_intersects(tags, table->tag)) {
+ struct cls_rule *rule = find_match(table, flow);
+ if (rule && (!best || rule->priority > best->priority)) {
+ best = rule;
+ }
}
}
return best;
@@ -489,12 +574,17 @@ find_table(const struct classifier *cls, const struct
minimask *mask)
static struct cls_table *
insert_table(struct classifier *cls, const struct minimask *mask)
{
+ uint32_t hash = minimask_hash(mask, 0);
struct cls_table *table;
table = xzalloc(sizeof *table);
hmap_init(&table->rules);
minimask_clone(&table->mask, mask);
- hmap_insert(&cls->tables, &table->hmap_node, minimask_hash(mask, 0));
+ hmap_insert(&cls->tables, &table->hmap_node, hash);
+
+ table->tag = (minimask_get_reg_mask(mask, 0) == UINT32_MAX
+ ? tag_create_deterministic(hash)
+ : TAG_ALL);
return table;
}
diff --git a/lib/classifier.h b/lib/classifier.h
index bc9db33..fdc7003 100644
--- a/lib/classifier.h
+++ b/lib/classifier.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2009, 2010, 2011, 2012 Nicira, Inc.
+ * Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -19,17 +19,65 @@
/* Flow classifier.
*
- * A classifier is a "struct classifier",
- * a hash map from a set of wildcards to a "struct cls_table",
- * a hash map from fixed field values to "struct cls_rule",
- * which can contain a list of otherwise identical rules
- * with lower priorities.
+ * Basic Design
+ * ============
+ *
+ * Suppose that all the rules in a classifier had the same form. For example,
+ * suppose that they all matched on the source and destination Ethernet address
+ * and wildcarded all the other fields. Then the obvious way to implement a
+ * classifier would be a hash table on the source and destination Ethernet
+ * addresses. If new classification rules came along with a different form,
+ * you could add a second hash table that hashed on the fields matched in those
+ * rules. With two hash tables, you look up a given flow in each hash table.
+ * If there are no matches, the classifier didn't contain a match; if you find
+ * a match in one of them, that's the result; if you find a match in both of
+ * them, then the result is the rule with the higher priority.
+ *
+ * This is how the classifier works. In a "struct classifier", each form of
+ * "struct cls_rule" present (based on its ->match.mask) goes into a separate
+ * "struct cls_table". A lookup does a hash lookup in every "struct cls_table"
+ * in the classifier and returns the highest-priority match that it finds.
+ *
+ * One detail: a classifier can contain multiple rules that are identical other
+ * than their priority. When this happens, only the highest priority rule out
+ * of a group of otherwise identical rules is stored directly in the "struct
+ * cls_table", with the other almost-identical rules chained off a linked list
+ * inside that highest-priority rule.
+ *
+ *
+ * Partitioning
+ * ============
+ *
+ * Suppose that a given classifier is being used to handle multiple stages in a
+ * pipeline using "resubmit", with reg0 distinguishing between the different
+ * stages. For example, reg0 value 1 might identify ingress rules, reg0 value
+ * 2 might identify ACLs, and reg0 value 3 might identify egress rules. Such a
+ * classifier is essentially partitioned into multiple sub-classifiers on the
+ * basis of the reg0 value.
+ *
+ * The classifier has a special optimization to speed up matching in this
+ * scenario:
+ *
+ * - Each cls_table that matches on reg0 gets a random tag (see tag.h).
+ *
+ * - For each reg0 value matched by any cls_rule, the classifier constructs
+ * a "struct cls_partition" indexed by the reg0 value. The cls_partition
+ * has a 'tags' member whose value is the bitwise-OR of the tags of each
+ * cls_table that contains any rule that matches on the cls_partition's
+ * reg0 value.
+ *
+ * Thus, a flow lookup can start by looking up the partition associated with
+ * the flow's reg0, and then skip over any cls_table whose 'tag' does not
+ * intersect the partition's 'tags'. (The flow must also be looked up in any
+ * cls_table that doesn't match on reg0. We handle that by giving any such
+ * cls_table TAG_ALL as its 'tags' so that it matches any tag.)
*/
#include "flow.h"
#include "hmap.h"
#include "list.h"
#include "match.h"
+#include "tag.h"
#include "openflow/nicira-ext.h"
#include "openflow/openflow.h"
@@ -41,6 +89,7 @@ extern "C" {
struct classifier {
int n_rules; /* Total number of rules. */
struct hmap tables; /* Contains "struct cls_table"s. */
+ struct hmap partitions; /* Contains "struct cls_partition"s. */
};
/* A set of rules that all have the same fields wildcarded. */
@@ -49,6 +98,7 @@ struct cls_table {
struct hmap rules; /* Contains "struct cls_rule"s. */
struct minimask mask; /* Wildcards for fields. */
int n_table_rules; /* Number of rules, including duplicates. */
+ tag_type tag; /* Tag generated from mask for partitioning. */
};
/* Returns true if 'table' is a "catch-all" table that will match every
@@ -65,6 +115,16 @@ struct cls_rule {
struct list list; /* List of identical, lower-priority rules. */
struct minimatch match; /* Matching rule. */
unsigned int priority; /* Larger numbers are higher priorities. */
+ struct cls_partition *partition;
+};
+
+/* Associates a reg0 value with tags for the "cls_table"s that contain rules
+ * that match that reg0 value. */
+struct cls_partition {
+ struct hmap_node hmap_node; /* In struct classifier's 'partitions' hmap. */
+ uint32_t reg0; /* reg0 value for this partition. */
+ unsigned int n_refs; /* # of flows that refer to this partition. */
+ tag_type tags; /* OR of each included flow's cls_table tag. */
};
void cls_rule_init(struct cls_rule *, const struct match *,
diff --git a/lib/flow.h b/lib/flow.h
index 8e79e62..b5c8827 100644
--- a/lib/flow.h
+++ b/lib/flow.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -251,6 +251,7 @@ void miniflow_expand(const struct miniflow *, struct flow
*);
uint32_t miniflow_get(const struct miniflow *, unsigned int u32_ofs);
uint16_t miniflow_get_vid(const struct miniflow *);
+static inline uint32_t miniflow_get_reg(const struct miniflow *, int index);
bool miniflow_equal(const struct miniflow *a, const struct miniflow *b);
bool miniflow_equal_in_minimask(const struct miniflow *a,
@@ -283,11 +284,35 @@ void minimask_expand(const struct minimask *, struct
flow_wildcards *);
uint32_t minimask_get(const struct minimask *, unsigned int u32_ofs);
uint16_t minimask_get_vid_mask(const struct minimask *);
+static inline uint32_t minimask_get_reg_mask(const struct minimask *,
+ int index);
bool minimask_equal(const struct minimask *a, const struct minimask *b);
uint32_t minimask_hash(const struct minimask *, uint32_t basis);
bool minimask_has_extra(const struct minimask *, const struct minimask *);
bool minimask_is_catchall(const struct minimask *);
+
+/* Returns the value of register 'index' in 'flow'. */
+static inline uint32_t
+miniflow_get_reg(const struct miniflow *flow, int index)
+{
+ enum { REG_OFS = offsetof(struct flow, regs) };
+
+ BUILD_ASSERT_DECL(REG_OFS % sizeof(uint32_t) == 0);
+
+ return miniflow_get(flow, REG_OFS / sizeof(uint32_t) + index);
+}
+
+/* Returns the mask for register 'index' in 'mask'.
+ *
+ * The return value is UINT32_MAX if 'mask' matches on the whole value of the
+ * register, 0 if 'mask' entirely wildcards the register, or some other value
+ * if the register is partially matched, partially wildcarded. */
+static inline uint32_t
+minimask_get_reg_mask(const struct minimask *mask, int index)
+{
+ return miniflow_get_reg(&mask->masks, index);
+}
#endif /* flow.h */
diff --git a/lib/tag.h b/lib/tag.h
index 2050de0..5d7c65b 100644
--- a/lib/tag.h
+++ b/lib/tag.h
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2008, 2011 Nicira, Inc.
+ * Copyright (c) 2008, 2011, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -69,6 +69,12 @@
/* Represents a tag, or the combination of 0 or more tags. */
typedef uint32_t tag_type;
+/* A 'tag_type' value that intersects every tag. */
+#define TAG_ALL UINT32_MAX
+
+/* An arbitrary tag. */
+#define TAG_ARBITRARY UINT32_C(3)
+
tag_type tag_create_random(void);
tag_type tag_create_deterministic(uint32_t seed);
static inline bool tag_intersects(tag_type, tag_type);
--
1.7.2.5
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