On Wed, Sep 22, 2021 at 4:47 PM Ilya Maximets <[email protected]> wrote: > > Current algorithm of ovsdb_datum_union looks like this: > > for-each atom in b: > if not bin_search(a, atom): > push(a, clone(atom)) > quicksort(a) > > So, the complexity looks like this: > > Nb * log2(Na) + Nb + (Na + Nb) * log2(Na + Nb) > Comparisons clones Comparisons for quicksort > for search > > ovsdb_datum_union() is heavily used in database transactions while > new element is added to a set. For example, if new logical switch > port is added to a logical switch in OVN. This is a very common > use case where CMS adds one new port to an existing switch that > already has, let's say, 100 ports. For this case ovsdb-server will > have to perform: > > 1 * log2(100) + 1 clone + 101 * log2(101) > Comparisons Comparisons for > for search quicksort. > ~7 1 ~707 > Roughly 714 comparisons of atoms and 1 clone. > > Since binary search can give us position, where new atom should go > (it's the 'low' index after the search completion) for free, the > logic can be re-worked like this: > > copied = 0 > for-each atom in b: > desired_position = bin_search(a, atom) > push(result, a[ copied : desired_position - 1 ]) > copied = desired_position > push(result, clone(atom)) > push(result, a[ copied : Na ]) > swap(a, result) > > Complexity of this schema: > > Nb * log2(Na) + Nb + Na > Comparisons clones memory copy on push > for search > > 'swap' is just a swap of a few pointers. 'push' is not a 'clone', > but a simple memory copy of 'union ovsdb_atom'. > > In general, this schema substitutes complexity of a quicksort > with complexity of a memory copy of Na atom structures, where we're > not even copying strings that these atoms are pointing to. > > Complexity in the example above goes down from 714 comparisons > to 7 comparisons and memcpy of 100 * sizeof (union ovsdb_atom) bytes. > > General complexity of a memory copy should always be lower than > complexity of a quicksort, especially because these copies usually > performed in bulk, so this new schema should work faster for any input. > > All in all, this change allows to execute several times more > transactions per second for transactions that adds new entries to sets. > > Alternatively, union can be implemented as a linear merge of two > sorted arrays, but this will result in O(Na) comparisons, which > is more than Nb * log2(Na) in common case, since Na is usually > far bigger than Nb. Linear merge will also mean per-atom memory > copies instead of copying in bulk. > > 'replace' functionality of ovsdb_datum_union() had no users, so it > just removed. But it can easily be added back if needed in the future. > > Signed-off-by: Ilya Maximets <[email protected]> > --- > lib/db-ctl-base.c | 28 +++++++------ > lib/ovsdb-data.c | 103 ++++++++++++++++++++++++++++++---------------- > lib/ovsdb-data.h | 10 ++--- > lib/ovsdb-idl.c | 29 ++++++------- > ovsdb/mutation.c | 2 +- > vswitchd/bridge.c | 6 +-- > 6 files changed, 105 insertions(+), 73 deletions(-) > > diff --git a/lib/db-ctl-base.c b/lib/db-ctl-base.c > index 77cc76a9f..3923683fd 100644 > --- a/lib/db-ctl-base.c > +++ b/lib/db-ctl-base.c > @@ -314,15 +314,18 @@ get_row_by_id(struct ctl_context *ctx, > row, id->name_column, key, value); > > /* Extract the name from the column. */ > - const union ovsdb_atom *name; > + const union ovsdb_atom *name = NULL; > if (!id->key) { > name = datum->n == 1 ? &datum->keys[0] : NULL; > } else { > const union ovsdb_atom key_atom > = { .string = CONST_CAST(char *, id->key) }; > - unsigned int i = ovsdb_datum_find_key(datum, &key_atom, > - OVSDB_TYPE_STRING); > - name = i == UINT_MAX ? NULL : &datum->values[i]; > + unsigned int i; > + > + if (ovsdb_datum_find_key(datum, &key_atom, > + OVSDB_TYPE_STRING, &i)) { > + name = &datum->values[i]; > + } > } > if (!name) { > continue; > @@ -819,14 +822,14 @@ check_condition(const struct ovsdb_idl_table_class *table, > goto out; > } > > - idx = ovsdb_datum_find_key(have_datum, > - &want_key, column->type.key.type); > - if (idx == UINT_MAX && !is_set_operator(operator)) { > + bool found = ovsdb_datum_find_key(have_datum, &want_key, > + column->type.key.type, &idx); > + if (!found && !is_set_operator(operator)) { > retval = false; > } else { > struct ovsdb_datum a; > > - if (idx != UINT_MAX) { > + if (found) { > a.n = 1; > a.keys = &have_datum->values[idx]; > a.values = NULL; > @@ -992,9 +995,8 @@ cmd_get(struct ctl_context *ctx) > return; > } > > - idx = ovsdb_datum_find_key(datum, &key, > - column->type.key.type); > - if (idx == UINT_MAX) { > + if (!ovsdb_datum_find_key(datum, &key, > + column->type.key.type, &idx)) { > if (must_exist) { > ctl_error( > ctx, "no key \"%s\" in %s record \"%s\" column %s", > @@ -1375,7 +1377,7 @@ set_column(const struct ovsdb_idl_table_class *table, > ovsdb_atom_destroy(&value, column->type.value.type); > > ovsdb_datum_union(&datum, ovsdb_idl_read(row, column), > - &column->type, false); > + &column->type); > ovsdb_idl_txn_verify(row, column); > ovsdb_idl_txn_write(row, column, &datum); > } else { > @@ -1514,7 +1516,7 @@ cmd_add(struct ctl_context *ctx) > ovsdb_datum_destroy(&old, &column->type); > return; > } > - ovsdb_datum_union(&old, &add, type, false); > + ovsdb_datum_union(&old, &add, type); > ovsdb_datum_destroy(&add, type); > } > if (old.n > type->n_max) { > diff --git a/lib/ovsdb-data.c b/lib/ovsdb-data.c > index 1f491a98b..7f9ff83f4 100644 > --- a/lib/ovsdb-data.c > +++ b/lib/ovsdb-data.c > @@ -799,7 +799,7 @@ ovsdb_atom_check_constraints(const union ovsdb_atom *atom, > const struct ovsdb_base_type *base) > { > if (base->enum_ > - && ovsdb_datum_find_key(base->enum_, atom, base->type) == UINT_MAX) { > + && !ovsdb_datum_find_key(base->enum_, atom, base->type, NULL)) { > struct ovsdb_error *error; > struct ds actual = DS_EMPTY_INITIALIZER; > struct ds valid = DS_EMPTY_INITIALIZER; > @@ -1784,14 +1784,16 @@ ovsdb_datum_compare_3way(const struct ovsdb_datum *a, > a->n)); > } > > -/* If 'key' is one of the keys in 'datum', returns its index within 'datum', > - * otherwise UINT_MAX. 'key.type' must be the type of the atoms stored in the > - * 'keys' array in 'datum'. > +/* If 'key' is one of the keys in 'datum', returns 'true' and sets '*pos' to > + * its index within 'datum', otherwise returns 'false' and sets '*pos' to the > + * index where 'key' should have been. 'key.type' must be the type of the > + * atoms stored in the 'keys' array in 'datum'. > */ > -unsigned int > +bool > ovsdb_datum_find_key(const struct ovsdb_datum *datum, > const union ovsdb_atom *key, > - enum ovsdb_atomic_type key_type) > + enum ovsdb_atomic_type key_type, > + unsigned int *pos) > { > unsigned int low = 0; > unsigned int high = datum->n; > @@ -1803,10 +1805,16 @@ ovsdb_datum_find_key(const struct ovsdb_datum *datum, > } else if (cmp > 0) { > low = idx + 1; > } else { > - return idx; > + if (pos) { > + *pos = idx; > + } > + return true; > } > } > - return UINT_MAX; > + if (pos) { > + *pos = low; > + } > + return false; > } > > /* If 'key' and 'value' is one of the key-value pairs in 'datum', returns its > @@ -1821,10 +1829,11 @@ ovsdb_datum_find_key_value(const struct ovsdb_datum *datum, > const union ovsdb_atom *value, > enum ovsdb_atomic_type value_type) > { > - unsigned int idx = ovsdb_datum_find_key(datum, key, key_type); > - if (idx != UINT_MAX > - && value_type != OVSDB_TYPE_VOID > - && !ovsdb_atom_equals(&datum->values[idx], value, value_type)) { > + unsigned int idx; > + > + if (!ovsdb_datum_find_key(datum, key, key_type, &idx) > + || (value_type != OVSDB_TYPE_VOID > + && !ovsdb_atom_equals(&datum->values[idx], value, value_type))) { > idx = UINT_MAX; > } > return idx; > @@ -1948,38 +1957,62 @@ ovsdb_datum_add_unsafe(struct ovsdb_datum *datum, > } > } > > +/* Adds 'n' atoms starting from index 'start_idx' from 'src' to the end of > + * 'dst'. 'dst' should have enough memory allocated to hold the additional > + * 'n' atoms. Atoms are not cloned, i.e. 'dst' will reference the same data. > + * Caller also should take care of the result being sorted. */ > +static void > +ovsdb_datum_push_unsafe(struct ovsdb_datum *dst, > + const struct ovsdb_datum *src, > + unsigned int start_idx, unsigned int n, > + const struct ovsdb_type *type) > +{ > + memcpy(&dst->keys[dst->n], &src->keys[start_idx], n * sizeof src->keys[0]); > + if (type->value.type != OVSDB_TYPE_VOID) { > + memcpy(&dst->values[dst->n], &src->values[start_idx], > + n * sizeof src->values[0]); > + } > + dst->n += n; > +} > + > void > ovsdb_datum_union(struct ovsdb_datum *a, const struct ovsdb_datum *b, > - const struct ovsdb_type *type, bool replace) > + const struct ovsdb_type *type) > { > - unsigned int n; > - size_t bi; > + struct ovsdb_datum result; > + unsigned int copied, pos; > > - n = a->n; > - for (bi = 0; bi < b->n; bi++) { > - unsigned int ai; > + ovsdb_datum_init_empty(&result); > + ovsdb_datum_reallocate(&result, type, a->n + b->n);
When the key(s) already exists, it doesn't need to call reallocate. Probably it is better to keep the behavior of the old implementation for this case, i.e. don't reallocate until the first new key is encountered. Other than this: Acked-by: Han Zhou <[email protected]> > > - ai = ovsdb_datum_find_key(a, &b->keys[bi], type->key.type); > - if (ai == UINT_MAX) { > - if (n == a->n) { > - ovsdb_datum_reallocate(a, type, a->n + (b->n - bi)); > - } > - ovsdb_atom_clone(&a->keys[n], &b->keys[bi], type->key.type); > - if (type->value.type != OVSDB_TYPE_VOID) { > - ovsdb_atom_clone(&a->values[n], &b->values[bi], > - type->value.type); > - } > - n++; > - } else if (replace && type->value.type != OVSDB_TYPE_VOID) { > - ovsdb_atom_destroy(&a->values[ai], type->value.type); > - ovsdb_atom_clone(&a->values[ai], &b->values[bi], > + copied = 0; > + for (size_t bi = 0; bi < b->n; bi++) { > + if (ovsdb_datum_find_key(a, &b->keys[bi], type->key.type, &pos)) { > + /* Atom with the same key already exists. */ > + continue; > + } > + if (pos > copied) { > + /* Need to copy some atoms from 'a' first. */ > + ovsdb_datum_push_unsafe(&result, a, copied, pos - copied, type); > + copied = pos; > + } > + /* Inserting new atom from 'b'. */ > + ovsdb_atom_clone(&result.keys[result.n], &b->keys[bi], type->key.type); > + if (type->value.type != OVSDB_TYPE_VOID) { > + ovsdb_atom_clone(&result.values[result.n], &b->values[bi], > type->value.type); > } > + result.n++; > } > - if (n != a->n) { > - a->n = n; > - ovs_assert(!ovsdb_datum_sort(a, type->key.type)); > + if (a->n > copied) { > + /* Copying remaining atoms. */ > + ovsdb_datum_push_unsafe(&result, a, copied, a->n - copied, type); > } > + /* All atoms are copied now. */ > + a->n = 0; > + > + ovsdb_datum_swap(&result, a); > + ovsdb_datum_destroy(&result, type); > } > > void > diff --git a/lib/ovsdb-data.h b/lib/ovsdb-data.h > index aa035ebad..4581e792f 100644 > --- a/lib/ovsdb-data.h > +++ b/lib/ovsdb-data.h > @@ -209,9 +209,10 @@ bool ovsdb_datum_equals(const struct ovsdb_datum *, > const struct ovsdb_type *); > > /* Search. */ > -unsigned int ovsdb_datum_find_key(const struct ovsdb_datum *, > - const union ovsdb_atom *key, > - enum ovsdb_atomic_type key_type); > +bool ovsdb_datum_find_key(const struct ovsdb_datum *, > + const union ovsdb_atom *key, > + enum ovsdb_atomic_type key_type, > + unsigned int *pos); > unsigned int ovsdb_datum_find_key_value(const struct ovsdb_datum *, > const union ovsdb_atom *key, > enum ovsdb_atomic_type key_type, > @@ -227,8 +228,7 @@ bool ovsdb_datum_excludes_all(const struct ovsdb_datum *, > const struct ovsdb_type *); > void ovsdb_datum_union(struct ovsdb_datum *, > const struct ovsdb_datum *, > - const struct ovsdb_type *, > - bool replace); > + const struct ovsdb_type *); > void ovsdb_datum_subtract(struct ovsdb_datum *a, > const struct ovsdb_type *a_type, > const struct ovsdb_datum *b, > diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c > index d3caccec8..c9c567e2c 100644 > --- a/lib/ovsdb-idl.c > +++ b/lib/ovsdb-idl.c > @@ -2840,9 +2840,8 @@ ovsdb_idl_txn_extract_mutations(struct ovsdb_idl_row *row, > struct ovsdb_datum *new_datum; > unsigned int pos; > new_datum = map_op_datum(map_op); > - pos = ovsdb_datum_find_key(old_datum, > - &new_datum->keys[0], > - key_type); > + ovsdb_datum_find_key(old_datum, &new_datum->keys[0], > + key_type, &pos); > if (ovsdb_atom_equals(&new_datum->values[0], > &old_datum->values[pos], > value_type)) { > @@ -2851,11 +2850,9 @@ ovsdb_idl_txn_extract_mutations(struct ovsdb_idl_row *row, > } > } else if (map_op_type(map_op) == MAP_OP_DELETE){ > /* Verify that there is a key to delete. */ > - unsigned int pos; > - pos = ovsdb_datum_find_key(old_datum, > - &map_op_datum(map_op)->keys[0], > - key_type); > - if (pos == UINT_MAX) { > + if (!ovsdb_datum_find_key(old_datum, > + &map_op_datum(map_op)->keys[0], > + key_type, NULL)) { > /* No key to delete. Move on to next update. */ > VLOG_WARN("Trying to delete a key that doesn't " > "exist in the map."); > @@ -2950,11 +2947,9 @@ ovsdb_idl_txn_extract_mutations(struct ovsdb_idl_row *row, > any_ins = true; > } else { /* SETP_OP_DELETE */ > /* Verify that there is a key to delete. */ > - unsigned int pos; > - pos = ovsdb_datum_find_key(old_datum, > - &set_op_datum(set_op)->keys[0], > - key_type); > - if (pos == UINT_MAX) { > + if (!ovsdb_datum_find_key(old_datum, > + &set_op_datum(set_op)->keys[0], > + key_type, NULL)) { > /* No key to delete. Move on to next update. */ > VLOG_WARN("Trying to delete a key that doesn't " > "exist in the set."); > @@ -4119,7 +4114,6 @@ ovsdb_idl_txn_write_partial_map(const struct ovsdb_idl_row *row_, > struct ovsdb_idl_row *row = CONST_CAST(struct ovsdb_idl_row *, row_); > enum ovsdb_atomic_type key_type; > enum map_op_type op_type; > - unsigned int pos; > const struct ovsdb_datum *old_datum; > > if (!is_valid_partial_update(row, column, datum)) { > @@ -4131,8 +4125,11 @@ ovsdb_idl_txn_write_partial_map(const struct ovsdb_idl_row *row_, > /* Find out if this is an insert or an update. */ > key_type = column->type.key.type; > old_datum = ovsdb_idl_read(row, column); > - pos = ovsdb_datum_find_key(old_datum, &datum->keys[0], key_type); > - op_type = pos == UINT_MAX ? MAP_OP_INSERT : MAP_OP_UPDATE; > + if (ovsdb_datum_find_key(old_datum, &datum->keys[0], key_type, NULL)) { > + op_type = MAP_OP_UPDATE; > + } else { > + op_type = MAP_OP_INSERT; > + } > > ovsdb_idl_txn_add_map_op(row, column, datum, op_type); > } > diff --git a/ovsdb/mutation.c b/ovsdb/mutation.c > index 56edc5f00..03d1c3499 100644 > --- a/ovsdb/mutation.c > +++ b/ovsdb/mutation.c > @@ -383,7 +383,7 @@ ovsdb_mutation_set_execute(struct ovsdb_row *row, > break; > > case OVSDB_M_INSERT: > - ovsdb_datum_union(dst, arg, dst_type, false); > + ovsdb_datum_union(dst, arg, dst_type); > error = ovsdb_mutation_check_count(dst, dst_type); > break; > > diff --git a/vswitchd/bridge.c b/vswitchd/bridge.c > index cb7c5cb76..c790a56ad 100644 > --- a/vswitchd/bridge.c > +++ b/vswitchd/bridge.c > @@ -4229,7 +4229,7 @@ bridge_configure_aa(struct bridge *br) > union ovsdb_atom atom; > > atom.integer = m->isid; > - if (ovsdb_datum_find_key(mc, &atom, OVSDB_TYPE_INTEGER) == UINT_MAX) { > + if (!ovsdb_datum_find_key(mc, &atom, OVSDB_TYPE_INTEGER, NULL)) { > VLOG_INFO("Deleting isid=%"PRIu32", vlan=%"PRIu16, > m->isid, m->vlan); > bridge_aa_mapping_destroy(m); > @@ -4826,7 +4826,7 @@ queue_ids_include(const struct ovsdb_datum *queues, int64_t target) > union ovsdb_atom atom; > > atom.integer = target; > - return ovsdb_datum_find_key(queues, &atom, OVSDB_TYPE_INTEGER) != UINT_MAX; > + return ovsdb_datum_find_key(queues, &atom, OVSDB_TYPE_INTEGER, NULL); > } > > static void > @@ -5020,7 +5020,7 @@ bridge_configure_mirrors(struct bridge *br) > union ovsdb_atom atom; > > atom.uuid = m->uuid; > - if (ovsdb_datum_find_key(mc, &atom, OVSDB_TYPE_UUID) == UINT_MAX) { > + if (!ovsdb_datum_find_key(mc, &atom, OVSDB_TYPE_UUID, NULL)) { > mirror_destroy(m); > } > } > -- > 2.31.1 > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
