/*
- * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
+ * Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* cls_subtable", with the other almost-identical rules chained off a linked
* list inside that highest-priority rule.
*
+ * The following sub-sections describe various optimizations over this simple
+ * approach.
+ *
*
* Staged Lookup (Wildcard Optimization)
- * =====================================
+ * -------------------------------------
*
* Subtable lookup is performed in ranges defined for struct flow, starting
* from metadata (registers, in_port, etc.), then L2 header, L3, and finally
*
*
* Prefix Tracking (Wildcard Optimization)
- * =======================================
+ * ---------------------------------------
*
* Classifier uses prefix trees ("tries") for tracking the used
* address space, enabling skipping classifier tables containing
*
*
* Partitioning (Lookup Time and Wildcard Optimization)
- * ====================================================
+ * ----------------------------------------------------
*
* Suppose that a given classifier is being used to handle multiple stages in a
* pipeline using "resubmit", with metadata (that is, the OpenFlow 1.1+ field
* Each eliminated subtable lookup also reduces the amount of un-wildcarding.
*
*
+ * Classifier Versioning
+ * =====================
+ *
+ * Classifier lookups are always done in a specific classifier version, where
+ * a version is defined to be a natural number.
+ *
+ * When a new rule is added to a classifier, it is set to become visible in a
+ * specific version. If the version number used at insert time is larger than
+ * any version number currently used in lookups, the new rule is said to be
+ * invisible to lookups. This means that lookups won't find the rule, but the
+ * rule is immediately available to classifier iterations.
+ *
+ * Similarly, a rule can be marked as to be deleted in a future version. To
+ * delete a rule in a way to not remove the rule before all ongoing lookups are
+ * finished, the rule should be made invisible in a specific version number.
+ * Then, when all the lookups use a later version number, the rule can be
+ * actually removed from the classifier.
+ *
+ * Classifiers can hold duplicate rules (rules with the same match criteria and
+ * priority) when at most one of these duplicates is visible in any given
+ * lookup version. The caller responsible for classifier modifications must
+ * maintain this invariant.
+ *
+ * The classifier supports versioning for two reasons:
+ *
+ * 1. Support for versioned modifications makes it possible to perform an
+ * arbitraty series of classifier changes as one atomic transaction,
+ * where intermediate versions of the classifier are not visible to any
+ * lookups. Also, when a rule is added for a future version, or marked
+ * for removal after the current version, such modifications can be
+ * reverted without any visible effects to any of the current lookups.
+ *
+ * 2. Performance: Adding (or deleting) a large set of rules can, in
+ * pathological cases, have a cost proportional to the number of rules
+ * already in the classifier. When multiple rules are being added (or
+ * deleted) in one go, though, this pathological case cost can be
+ * typically avoided, as long as it is OK for any new rules to be
+ * invisible until the batch change is complete.
+ *
+ * Note that the classifier_replace() function replaces a rule immediately, and
+ * is therefore not safe to use with versioning. It is still available for the
+ * users that do not use versioning.
+ *
+ *
+ * Deferred Publication
+ * ====================
+ *
+ * Removing large number of rules from classifier can be costly, as the
+ * supporting data structures are teared down, in many cases just to be
+ * re-instantiated right after. In the worst case, as when each rule has a
+ * different match pattern (mask), the maintenance of the match patterns can
+ * have cost O(N^2), where N is the number of different match patterns. To
+ * alleviate this, the classifier supports a "deferred mode", in which changes
+ * in internal data structures needed for future version lookups may not be
+ * fully computed yet. The computation is finalized when the deferred mode is
+ * turned off.
+ *
+ * This feature can be used with versioning such that all changes to future
+ * versions are made in the deferred mode. Then, right before making the new
+ * version visible to lookups, the deferred mode is turned off so that all the
+ * data structures are ready for lookups with the new version number.
+ *
+ * To use deferred publication, first call classifier_defer(). Then, modify
+ * the classifier via additions (classifier_insert() with a specific, future
+ * version number) and deletions (use cls_rule_make_removable_after_version()).
+ * Then call classifier_publish(), and after that, announce the new version
+ * number to be used in lookups.
+ *
+ *
* Thread-safety
* =============
*
- * The classifier may safely be accessed by many reader threads concurrently or
- * by a single writer. */
+ * The classifier may safely be accessed by many reader threads concurrently
+ * and by a single writer, or by multiple writers when they guarantee mutually
+ * exlucive access to classifier modifications.
+ *
+ * Since the classifier rules are RCU protected, the rule destruction after
+ * removal from the classifier must be RCU postponed. Also, when versioning is
+ * used, the rule removal itself needs to be typically RCU postponed. In this
+ * case the rule destruction is doubly RCU postponed, i.e., the second
+ * ovsrcu_postpone() call to destruct the rule is called from the first RCU
+ * callback that removes the rule.
+ *
+ * Rules that have never been visible to lookups are an exeption to the above
+ * rule. Such rules can be removed immediately, but their destruction must
+ * still be RCU postponed, as the rule's visibility attribute may be examined
+ * parallel to the rule's removal. */
#include "cmap.h"
#include "match.h"
#include "meta-flow.h"
-#include "ovs-thread.h"
#include "pvector.h"
+#include "rculist.h"
+#include "type-props.h"
#ifdef __cplusplus
extern "C" {
rcu_trie_ptr root; /* NULL if none. */
};
+typedef uint64_t cls_version_t;
+
+#define CLS_MIN_VERSION 0 /* Default version number to use. */
+#define CLS_MAX_VERSION (TYPE_MAXIMUM(cls_version_t) - 1)
+#define CLS_NOT_REMOVED_VERSION TYPE_MAXIMUM(cls_version_t)
+
enum {
CLS_MAX_INDICES = 3, /* Maximum number of lookup indices per subtable. */
CLS_MAX_TRIES = 3 /* Maximum number of prefix trees per classifier. */
/* A flow classifier. */
struct classifier {
- struct ovs_mutex mutex;
- int n_rules OVS_GUARDED; /* Total number of rules. */
+ int n_rules; /* Total number of rules. */
uint8_t n_flow_segments;
uint8_t flow_segments[CLS_MAX_INDICES]; /* Flow segment boundaries to use
* for staged lookup. */
struct cmap partitions; /* Contains "struct cls_partition"s. */
struct cls_trie tries[CLS_MAX_TRIES]; /* Prefix tries. */
unsigned int n_tries;
+ bool publish; /* Make changes visible to lookups? */
+};
+
+struct cls_conjunction {
+ uint32_t id;
+ uint8_t clause;
+ uint8_t n_clauses;
};
/* A rule to be inserted to the classifier. */
struct cls_rule {
- struct minimatch match; /* Matching rule. */
- unsigned int priority; /* Larger numbers are higher priorities. */
- struct cls_match *cls_match; /* NULL if rule is not in a classifier. */
+ struct rculist node; /* In struct cls_subtable 'rules_list'. */
+ const int priority; /* Larger numbers are higher priorities. */
+ struct cls_match *cls_match; /* NULL if not in a classifier. */
+ const struct minimatch match; /* Matching rule. */
};
-void cls_rule_init(struct cls_rule *, const struct match *,
- unsigned int priority);
+void cls_rule_init(struct cls_rule *, const struct match *, int priority);
void cls_rule_init_from_minimatch(struct cls_rule *, const struct minimatch *,
- unsigned int priority);
+ int priority);
void cls_rule_clone(struct cls_rule *, const struct cls_rule *);
void cls_rule_move(struct cls_rule *dst, struct cls_rule *src);
void cls_rule_destroy(struct cls_rule *);
-bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
-uint32_t cls_rule_hash(const struct cls_rule *, uint32_t basis);
+void cls_rule_set_conjunctions(struct cls_rule *,
+ const struct cls_conjunction *, size_t n);
+bool cls_rule_equal(const struct cls_rule *, const struct cls_rule *);
void cls_rule_format(const struct cls_rule *, struct ds *);
-
bool cls_rule_is_catchall(const struct cls_rule *);
-
bool cls_rule_is_loose_match(const struct cls_rule *rule,
const struct minimatch *criteria);
+bool cls_rule_visible_in_version(const struct cls_rule *, cls_version_t);
+void cls_rule_make_invisible_in_version(const struct cls_rule *,
+ cls_version_t);
+void cls_rule_restore_visibility(const struct cls_rule *);
+/* Constructor/destructor. Must run single-threaded. */
void classifier_init(struct classifier *, const uint8_t *flow_segments);
void classifier_destroy(struct classifier *);
+
+/* Modifiers. Caller MUST exclude concurrent calls from other threads. */
bool classifier_set_prefix_fields(struct classifier *,
const enum mf_field_id *trie_fields,
unsigned int n_trie_fields);
+void classifier_insert(struct classifier *, const struct cls_rule *,
+ cls_version_t, const struct cls_conjunction *,
+ size_t n_conjunctions);
+const struct cls_rule *classifier_replace(struct classifier *,
+ const struct cls_rule *,
+ cls_version_t,
+ const struct cls_conjunction *,
+ size_t n_conjunctions);
+const struct cls_rule *classifier_remove(struct classifier *,
+ const struct cls_rule *);
+static inline void classifier_defer(struct classifier *);
+static inline void classifier_publish(struct classifier *);
+/* Lookups. These are RCU protected and may run concurrently with modifiers
+ * and each other. */
+const struct cls_rule *classifier_lookup(const struct classifier *,
+ cls_version_t, struct flow *,
+ struct flow_wildcards *);
+bool classifier_rule_overlaps(const struct classifier *,
+ const struct cls_rule *, cls_version_t);
+const struct cls_rule *classifier_find_rule_exactly(const struct classifier *,
+ const struct cls_rule *,
+ cls_version_t);
+const struct cls_rule *classifier_find_match_exactly(const struct classifier *,
+ const struct match *,
+ int priority,
+ cls_version_t);
bool classifier_is_empty(const struct classifier *);
int classifier_count(const struct classifier *);
-void classifier_insert(struct classifier *, struct cls_rule *);
-struct cls_rule *classifier_replace(struct classifier *, struct cls_rule *);
-
-void classifier_remove(struct classifier *, struct cls_rule *);
-struct cls_rule *classifier_lookup(const struct classifier *,
- const struct flow *,
- struct flow_wildcards *);
-bool classifier_lookup_miniflow_batch(const struct classifier *cls,
- const struct miniflow **flows,
- struct cls_rule **rules, size_t len);
-bool classifier_rule_overlaps(const struct classifier *,
- const struct cls_rule *);
-
-struct cls_rule *classifier_find_rule_exactly(const struct classifier *,
- const struct cls_rule *);
-
-struct cls_rule *classifier_find_match_exactly(const struct classifier *,
- const struct match *,
- unsigned int priority);
\f
-/* Iteration. */
-
+/* Iteration.
+ *
+ * Iteration is lockless and RCU-protected. Concurrent threads may perform all
+ * kinds of concurrent modifications without ruining the iteration. Obviously,
+ * any modifications may or may not be visible to the concurrent iterator, but
+ * all the rules not deleted are visited by the iteration. The iterating
+ * thread may also modify the classifier rules itself.
+ *
+ * 'TARGET' iteration only iterates rules matching the 'TARGET' criteria.
+ * Rather than looping through all the rules and skipping ones that can't
+ * match, 'TARGET' iteration skips whole subtables, if the 'TARGET' happens to
+ * be more specific than the subtable. */
struct cls_cursor {
const struct classifier *cls;
const struct cls_subtable *subtable;
const struct cls_rule *target;
- struct cmap_cursor subtables;
- struct cmap_cursor rules;
- struct cls_rule *rule;
- bool safe;
+ cls_version_t version; /* Version to iterate. */
+ struct pvector_cursor subtables;
+ const struct cls_rule *rule;
};
-/* Iteration requires mutual exclusion of writers. We do this by taking
- * a mutex for the duration of the iteration, except for the
- * 'SAFE' variant, where we release the mutex for the body of the loop. */
-struct cls_cursor cls_cursor_start(const struct classifier *cls,
+struct cls_cursor cls_cursor_start(const struct classifier *,
const struct cls_rule *target,
- bool safe);
-
+ cls_version_t);
void cls_cursor_advance(struct cls_cursor *);
-#define CLS_FOR_EACH(RULE, MEMBER, CLS) \
- CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, NULL)
-#define CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, TARGET) \
- for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, false); \
- (cursor__.rule \
- ? (INIT_CONTAINER(RULE, cursor__.rule, MEMBER), \
- true) \
- : false); \
- cls_cursor_advance(&cursor__))
-
-/* These forms allows classifier_remove() to be called within the loop. */
-#define CLS_FOR_EACH_SAFE(RULE, MEMBER, CLS) \
- CLS_FOR_EACH_TARGET_SAFE(RULE, MEMBER, CLS, NULL)
-#define CLS_FOR_EACH_TARGET_SAFE(RULE, MEMBER, CLS, TARGET) \
- for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, true); \
+#define CLS_FOR_EACH(RULE, MEMBER, CLS) \
+ CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, NULL, CLS_MAX_VERSION)
+#define CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, TARGET, VERSION) \
+ for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, VERSION); \
(cursor__.rule \
? (INIT_CONTAINER(RULE, cursor__.rule, MEMBER), \
cls_cursor_advance(&cursor__), \
true) \
: false); \
- ) \
+ )
+
+\f
+static inline void
+classifier_defer(struct classifier *cls)
+{
+ cls->publish = false;
+}
+
+static inline void
+classifier_publish(struct classifier *cls)
+{
+ cls->publish = true;
+ pvector_publish(&cls->subtables);
+}
#ifdef __cplusplus
}
#endif
-
#endif /* classifier.h */
projects / cascardo / ovs.git / blobdiff