* Each eliminated subtable lookup also reduces the amount of un-wildcarding.
*
*
- * Tentative Modifications
- * =======================
- *
- * When a new rule is added to a classifier, it can optionally be "invisible".
- * That means that lookups won't find the rule, although iterations through
- * the classifier will see it.
+ * Classifier Versioning
+ * =====================
*
- * Similarly, deletions from a classifier can be "tentative", by setting
- * 'to_be_removed' to true within the rule. A rule that is tentatively deleted
- * will not appear in iterations, although it will still be found by lookups.
- *
- * Classifiers can hold duplicate rules (rules with the same match criteria and
- * priority) when tentative modifications are involved: one (or more) identical
- * tentatively deleted rules can coexist in a classifier with at most one
- * identical invisible rule.
+ * Classifier lookups are always done in a specific classifier version, where
+ * a version is defined to be a natural number.
*
- * The classifier supports tentative modifications for two reasons:
+ * 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.
*
- * 1. Performance: Adding (or deleting) a rule 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 cost can be paid just once, not once per addition
- * (or deletion), as long as it is OK for any new rules to be invisible
- * until the batch change is complete.
+ * 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.
*
- * 2. Staging additions and deletions: Invisibility allows a rule to be
- * added tentatively, to possibly be modified or removed before it
- * becomes visible. Tentatively deletion allows a rule to be scheduled
- * for deletion before it is certain that the deletion is desirable.
+ * 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 and deletions. Call cls_rule_make_visible() on
- * each new rule at an appropriate time. Finally, call classifier_publish().
+ * 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 "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 rule to be inserted to the classifier. */
struct cls_rule {
- struct rculist node; /* In struct cls_subtable 'rules_list'. */
- int priority; /* Larger numbers are higher priorities. */
- bool to_be_removed; /* Rule will be deleted.
- * This is the only field that may be
- * modified after the rule has been added to
- * a classifier. Modifications are to be
- * done only under same locking as all other
- * classifier modifications. This field may
- * not be examined by lookups. */
- struct cls_match *cls_match; /* NULL if not in a classifier. */
- struct minimatch match; /* Matching rule. */
+ 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 *, int priority);
const struct cls_conjunction *, size_t n);
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_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);
-void cls_rule_make_visible(const struct cls_rule *rule);
+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);
const enum mf_field_id *trie_fields,
unsigned int n_trie_fields);
void classifier_insert(struct classifier *, const struct cls_rule *,
- const struct cls_conjunction *, size_t n_conjunctions);
+ 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 *,
/* Lookups. These are RCU protected and may run concurrently with modifiers
* and each other. */
const struct cls_rule *classifier_lookup(const struct classifier *,
- struct flow *,
+ cls_version_t, struct flow *,
struct flow_wildcards *);
bool classifier_rule_overlaps(const struct classifier *,
- const struct cls_rule *);
+ const struct cls_rule *, cls_version_t);
const struct cls_rule *classifier_find_rule_exactly(const struct classifier *,
- const struct cls_rule *);
+ const struct cls_rule *,
+ cls_version_t);
const struct cls_rule *classifier_find_match_exactly(const struct classifier *,
const struct match *,
- int priority);
+ int priority,
+ cls_version_t);
bool classifier_is_empty(const struct classifier *);
int classifier_count(const struct classifier *);
\f
const struct classifier *cls;
const struct cls_subtable *subtable;
const struct cls_rule *target;
+ cls_version_t version; /* Version to iterate. */
struct pvector_cursor subtables;
const struct cls_rule *rule;
};
-struct cls_cursor cls_cursor_start(const struct classifier *cls,
- const struct cls_rule *target);
+struct cls_cursor cls_cursor_start(const struct classifier *,
+ const struct cls_rule *target,
+ 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); \
+ 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__), \
: false); \
)
-#ifdef __cplusplus
-}
-#endif
\f
static inline void
classifier_defer(struct classifier *cls)
cls->publish = true;
pvector_publish(&cls->subtables);
}
+
+#ifdef __cplusplus
+}
+#endif
#endif /* classifier.h */
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