This commit refactors the generic implementation. The goal of this refactor is to simply the code to enable "specialization" of the functions at compile time.
Given compile-time optimizations, the compiler is able to unroll loops, and create optimized code sequences due to compile time knowledge of loop-trip counts. In order to enable these compiler optimizations, we must refactor the code to pass the loop-trip counts to functions as compile time constants. This patch allows the number of miniflow-bits set per "unit" in the miniflow to be passed around as a function argument. Note that this patch does NOT yet take advantage of doing so, this is only a refactor to enable it in the next patches. Signed-off-by: Harry van Haaren <[email protected]> --- lib/dpif-netdev-lookup-generic.c | 289 +++++++++++++++++++++++++------ lib/dpif-netdev.c | 8 +- lib/dpif-netdev.h | 7 + 3 files changed, 252 insertions(+), 52 deletions(-) diff --git a/lib/dpif-netdev-lookup-generic.c b/lib/dpif-netdev-lookup-generic.c index 2e4003408..770ef70d3 100644 --- a/lib/dpif-netdev-lookup-generic.c +++ b/lib/dpif-netdev-lookup-generic.c @@ -28,67 +28,254 @@ #include "packets.h" #include "pvector.h" -/* Returns a hash value for the bits of 'key' where there are 1-bits in - * 'mask'. */ -static inline uint32_t -netdev_flow_key_hash_in_mask(const struct netdev_flow_key *key, - const struct netdev_flow_key *mask) +VLOG_DEFINE_THIS_MODULE(dpif_lookup_generic); + +/* netdev_flow_key_flatten_unit: + * Given a packet, table and mf_masks, this function iterates over each bit + * set in the subtable, and calculates the appropriate metadata to store in the + * block_cache[]. + * + * The results of the block_cache[] can be used for hashing, and later for + * verification of if a rule matches the given packet. + */ +static inline void +netdev_flow_key_flatten_unit(const uint64_t * restrict pkt_blocks, + const uint64_t * restrict tbl_blocks, + const uint64_t * restrict mf_masks, + uint64_t * restrict block_cache, + const uint64_t pkt_mf_bits, + const uint32_t count) { - const uint64_t *p = miniflow_get_values(&mask->mf); - uint32_t hash = 0; - uint64_t value; + uint32_t i; + for (i = 0; i < count; i++) { + uint64_t mf_mask = mf_masks[i]; + /* Calculate the block index for the packet metadata */ + uint64_t idx_bits = mf_mask & pkt_mf_bits; + const uint32_t pkt_idx = __builtin_popcountll(idx_bits); + + /* check if the packet has the subtable miniflow bit set. If yes, the + * block at the above pkt_idx will be stored, otherwise it is masked + * out to be zero. + */ + uint64_t pkt_has_mf_bit = (mf_mask + 1) & pkt_mf_bits; + uint64_t no_bit = ((!pkt_has_mf_bit) > 0) - 1; - NETDEV_FLOW_KEY_FOR_EACH_IN_FLOWMAP (value, key, mask->mf.map) { - hash = hash_add64(hash, value & *p); - p++; + /* mask packet block by table block, and mask to zero if packet + * doesn't actually contain this block of metadata + */ + block_cache[i] = pkt_blocks[pkt_idx] & tbl_blocks[i] & no_bit; } +} + +/* netdev_flow_key_flatten: + * This function takes a packet, and subtable and writes an array of uint64_t + * blocks. The blocks contain the metadata that the subtable matches on, in + * the same order as the subtable, allowing linear iteration over the blocks. + * + * To calculate the blocks contents, the netdev_flow_key_flatten_unit function + * is called twice, once for each "unit" of the miniflow. This call can be + * inlined by the compiler for performance. + * + * Note that the u0_count and u1_count variables can be compile-time constants, + * allowing the loop in the inlined flatten_unit() function to be compile-time + * unrolled, or possibly removed totally by unrolling by the loop iterations. + * The compile time optimizations enabled by this design improves performance. + */ +static inline void +netdev_flow_key_flatten(const struct netdev_flow_key * restrict key, + const struct netdev_flow_key * restrict mask, + const uint64_t * restrict mf_masks, + uint64_t * restrict block_cache, + const uint32_t u0_count, + const uint32_t u1_count) +{ + /* load mask from subtable, mask with packet mf, popcount to get idx */ + const uint64_t *pkt_blocks = miniflow_get_values(&key->mf); + const uint64_t *tbl_blocks = miniflow_get_values(&mask->mf); + + /* packet miniflow bits to be masked by pre-calculated mf_masks */ + const uint64_t pkt_bits_u0 = key->mf.map.bits[0]; + const uint32_t pkt_bits_u0_pop = __builtin_popcountll(pkt_bits_u0); + const uint64_t pkt_bits_u1 = key->mf.map.bits[1]; - return hash_finish(hash, (p - miniflow_get_values(&mask->mf)) * 8); + /* Unit 0 flattening */ + netdev_flow_key_flatten_unit(&pkt_blocks[0], + &tbl_blocks[0], + &mf_masks[0], + &block_cache[0], + pkt_bits_u0, + u0_count); + + /* Unit 1 flattening: + * Move the pointers forward in the arrays based on u0 offsets, NOTE: + * 1) pkt blocks indexed by actual popcount of u0, which is NOT always + * the same as the amount of bits set in the subtable. + * 2) mf_masks, tbl_block and block_cache are all "flat" arrays, so + * the index is always u0_count. + */ + netdev_flow_key_flatten_unit(&pkt_blocks[pkt_bits_u0_pop], + &tbl_blocks[u0_count], + &mf_masks[u0_count], + &block_cache[u0_count], + pkt_bits_u1, + u1_count); } +/* inner loop for mask generation of a unit, see netdev_flow_key_gen_masks */ +static inline void +netdev_flow_key_gen_mask_unit(uint64_t iter, + const uint64_t count, + uint64_t *mf_masks) +{ + int i; + for (i = 0; i < count; i++) { + uint64_t lowest_bit = (iter & -iter); + iter &= ~lowest_bit; + mf_masks[i] = (lowest_bit - 1); + } + /* checks that count has covered all bits in the iter bitmap */ + ovs_assert(iter == 0); +} + +/* generate a mask for each block in the miniflow, based on the bits set. This + * allows easily masking packets with the generated array here, without + * calculations. This removes runtime-calculated masks, and hence data-deps. + * @param key The table to generate the mf_masks for + * @param mf_masks Pointer to a u64 array of at least *mf_bits* in size + * @param mf_bits_total Number of bits set in the whole miniflow (both units) + * @param mf_bits_unit0 Number of bits set in unit0 of the miniflow + */ +static inline void +netdev_flow_key_gen_masks(const struct netdev_flow_key * restrict tbl, + uint64_t * restrict mf_masks, + const uint32_t mf_bits_u0, + const uint32_t mf_bits_u1) +{ + uint64_t iter_u0 = tbl->mf.map.bits[0]; + uint64_t iter_u1 = tbl->mf.map.bits[1]; + + netdev_flow_key_gen_mask_unit(iter_u0, mf_bits_u0, &mf_masks[0]); + netdev_flow_key_gen_mask_unit(iter_u1, mf_bits_u1, &mf_masks[mf_bits_u0]); +} + + +static inline uint64_t +netdev_rule_matches_key(const struct dpcls_rule * restrict rule, + const struct netdev_flow_key *target, + const uint32_t mf_bits_total, + const uint64_t * restrict block_cache) +{ + const uint64_t *keyp = miniflow_get_values(&rule->flow.mf); + const uint64_t *maskp = miniflow_get_values(&rule->mask->mf); + + /* all meta-data is available in block_cache, no pkt miniflow required */ + (void)target; + + uint64_t not_match = 0; + for (int i = 0; i < mf_bits_total; i++) { + not_match |= (block_cache[i] & maskp[i]) != keyp[i]; + } + + /* invert result to show match as 1 */ + return !not_match; +} + +/* const prop version of the function: note that mf bits total and u0 are + * explicitly passed in here, while they're also available at runtime from the + * subtable pointer. By making them compile time, we enable the compiler to + * unroll loops and flatten out code-sequences based on the knowledge of the + * mf_bits_* compile time values. This results in improved performance. + */ +static inline uint32_t __attribute__((always_inline)) +lookup_generic_impl(struct dpcls_subtable *subtable, uint32_t keys_map, + const struct netdev_flow_key *keys[], + struct dpcls_rule **rules, + const uint32_t bit_count_u0, + const uint32_t bit_count_u1) +{ + const uint32_t bit_count_total = bit_count_u0 + bit_count_u1; + int i; + uint32_t hashes[NETDEV_MAX_BURST]; + const uint32_t n_pkts = __builtin_popcountll(keys_map); + ovs_assert(NETDEV_MAX_BURST >= n_pkts); + + /* Allocate stack space for storing miniflow blocks per packet */ + uint64_t block_cache[NETDEV_MAX_BURST * bit_count_total]; + + /* Calculate the subtable miniflow mask for each bit set. The masks are + * calculated once, and then re-used for all packets in keys_map. The + * mf_masks[] contains masks containing all bits set under the subtable + * bit. This enables performant linear iteration over the masks later. + */ + uint64_t mf_masks[bit_count_total]; + netdev_flow_key_gen_masks(&subtable->mask, mf_masks, bit_count_u0, + bit_count_u1); + + /* Flatten the packet metadata into the block_cache[] using subtable */ + ULLONG_FOR_EACH_1(i, keys_map) { + netdev_flow_key_flatten(keys[i], + &subtable->mask, + mf_masks, + &block_cache[i * bit_count_total], + bit_count_u0, + bit_count_u1); + } + + /* Hash the now linearized blocks of packet metadata */ + ULLONG_FOR_EACH_1(i, keys_map) { + uint32_t hash = 0; + uint32_t i_off = i * bit_count_total; + for (int h = 0; h < bit_count_total; h++) { + hash = hash_add64(hash, block_cache[i_off + h]); + } + hashes[i] = hash_finish(hash, bit_count_total * 8); + } + + /* Lookup: this returns a bitmask of packets where the hash table had + * an entry for the given hash key. Presence of a hash key does not + * guarantee matching the key, as there can be hash collisions. + */ + uint32_t found_map; + const struct cmap_node *nodes[NETDEV_MAX_BURST]; + found_map = cmap_find_batch(&subtable->rules, keys_map, hashes, nodes); + + /* Verify that packet actually matched rule. If not found, a hash + * collision has taken place, so continue searching with the next node. + */ + ULLONG_FOR_EACH_1(i, found_map) { + struct dpcls_rule *rule; + + CMAP_NODE_FOR_EACH (rule, cmap_node, nodes[i]) { + const uint32_t cidx = i * bit_count_total; + uint32_t match = netdev_rule_matches_key(rule, keys[i], + bit_count_total, + &block_cache[cidx]); + + if (OVS_LIKELY(match)) { + rules[i] = rule; + subtable->hit_cnt++; + goto next; + } + } + + /* None of the found rules was a match. Clear the i-th bit to + * search for this key in the next subtable. */ + ULLONG_SET0(found_map, i); + next: + ; /* Keep Sparse happy. */ + } + + return found_map; +} + +/* Generic - use runtime provided mf bits */ uint32_t dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable, uint32_t keys_map, const struct netdev_flow_key *keys[], struct dpcls_rule **rules) { - int i; - /* Compute hashes for the remaining keys. Each search-key is - * masked with the subtable's mask to avoid hashing the wildcarded - * bits. */ - uint32_t hashes[NETDEV_MAX_BURST]; - ULLONG_FOR_EACH_1(i, keys_map) { - hashes[i] = netdev_flow_key_hash_in_mask(keys[i], - &subtable->mask); - } - - /* Lookup. */ - const struct cmap_node *nodes[NETDEV_MAX_BURST]; - uint32_t found_map = - cmap_find_batch(&subtable->rules, keys_map, hashes, nodes); - /* Check results. When the i-th bit of found_map is set, it means - * that a set of nodes with a matching hash value was found for the - * i-th search-key. Due to possible hash collisions we need to check - * which of the found rules, if any, really matches our masked - * search-key. */ - ULLONG_FOR_EACH_1(i, found_map) { - struct dpcls_rule *rule; - - CMAP_NODE_FOR_EACH (rule, cmap_node, nodes[i]) { - if (OVS_LIKELY(dpcls_rule_matches_key(rule, keys[i]))) { - rules[i] = rule; - /* Even at 20 Mpps the 32-bit hit_cnt cannot wrap - * within one second optimization interval. */ - subtable->hit_cnt++; - goto next; - } - } - /* None of the found rules was a match. Reset the i-th bit to - * keep searching this key in the next subtable. */ - ULLONG_SET0(found_map, i); /* Did not match. */ - next: - ; /* Keep Sparse happy. */ - } - - return found_map; + return lookup_generic_impl(subtable, keys_map, keys, rules, + subtable->mf_bits_set_unit0, + subtable->mf_bits_set_unit1); } diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index fe7171baa..3bc826079 100644 --- a/lib/dpif-netdev.c +++ b/lib/dpif-netdev.c @@ -7589,7 +7589,13 @@ dpcls_create_subtable(struct dpcls *cls, const struct netdev_flow_key *mask) subtable->hit_cnt = 0; netdev_flow_key_clone(&subtable->mask, mask); - /* decide which hash/lookup/verify function to use */ + /* set the number of bits used max, used to allocate enough space for + * each packet to store all the blocks of metadata */ + uint32_t unit0 = __builtin_popcountll(mask->mf.map.bits[0]); + uint32_t unit1 = __builtin_popcountll(mask->mf.map.bits[1]); + subtable->mf_bits_set_unit0 = unit0; + subtable->mf_bits_set_unit1 = unit1; + subtable->lookup_func = dpcls_subtable_lookup_generic; cmap_insert(&cls->subtables_map, &subtable->cmap_node, mask->hash); diff --git a/lib/dpif-netdev.h b/lib/dpif-netdev.h index 27145d721..0911fa93c 100644 --- a/lib/dpif-netdev.h +++ b/lib/dpif-netdev.h @@ -92,6 +92,13 @@ struct dpcls_subtable { * subtable matches on. The miniflow "bits" are used to select the actual * dpcls lookup implementation at subtable creation time. */ + uint8_t mf_bits_set_unit0; + uint8_t mf_bits_set_unit1; + + /* the lookup function to use for this subtable. If there is a known + * property of the subtable (eg: only 3 bits of miniflow metadata is + * used for the lookup) then this can point at an optimized version of + * the lookup function for this particular subtable. */ dpcls_subtable_lookup_func lookup_func; struct netdev_flow_key mask; /* Wildcards for fields (const). */ -- 2.17.1 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
