This commit refactors the generic implementation. The goal of this refactor is to simplify 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 <harry.van.haa...@intel.com> Tested-by: Malvika Gupta <malvika.gu...@arm.com> --- v12: - Fix Caps and . (Ilya) - Fixed typos (Ilya) - Added mf_bits and mf_masks in this patch (Ilya) - Fixed rebase conflicts v11: - Rebased to previous changes - Fix typo in commit message (Ian) - Fix variable declaration spacing (Ian) - Remove function names from comments (Ian) - Replace magic 8 with sizeof(uint64_t) (Ian) - Captialize and end comments with a stop. (Ian/Ilya) - Add build time assert to validate FLOWMAP_UNITS (Ilya) - Add note on ALWAYS_INLINE operation - Add space after ULLONG_FOR_EACH_1 (Ilya) - Use hash_add_words64() instead of rolling own loop (Ilya) Note that hash_words64_inline() calls hash_finish() with an fixed value, so it was not the right hash function for this usage. Used hash_add_words64() and manual hash_finish() to re-use as much of hashing code as we can. v10: - Rebase updates from previous patches - Fix whitespace indentation of func params - Removed restrict keyword, Windows CI failing when it is used (Ian) - Fix integer 0 used to set NULL pointer (Ilya) - Postpone free() call on cls->blocks_scratch (Ilya) - Fix indentation of a function v9: - Use count_1bits in favour of __builtin_popcount (Ilya) - Use ALWAYS_INLINE instead of __attribute__ synatx (Ilya) v8: - Rework block_cache and mf_masks to avoid variable-lenght array due to compiler issues. Provisioning for worst case is not a good solution due to magnitue of over-provisioning required. - Rework netdev_flatten function removing unused parameter --- lib/dpif-netdev-lookup-generic.c | 205 ++++++++++++++++++++++++++----- lib/dpif-netdev-private.h | 14 ++- lib/dpif-netdev.c | 77 +++++++++++- 3 files changed, 261 insertions(+), 35 deletions(-) diff --git a/lib/dpif-netdev-lookup-generic.c b/lib/dpif-netdev-lookup-generic.c index 8064911b3..b38adc2d5 100644 --- a/lib/dpif-netdev-lookup-generic.c +++ b/lib/dpif-netdev-lookup-generic.c @@ -30,58 +30,186 @@ #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); + +/* Lookup functions below depends on the internal structure of flowmap. */ +BUILD_ASSERT_DECL(FLOWMAP_UNITS == 2); + +/* 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 + * blocks_scratch[]. + * + * The results of the blocks_scratch[] 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 *pkt_blocks, + const uint64_t *tbl_blocks, + const uint64_t *mf_masks, + uint64_t *blocks_scratch, + 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 = count_1bits(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. + */ + blocks_scratch[i] = pkt_blocks[pkt_idx] & tbl_blocks[i] & no_bit; } +} + +/* 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 *key, + const struct netdev_flow_key *mask, + const uint64_t *mf_masks, + uint64_t *blocks_scratch, + 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); - return hash_finish(hash, (p - miniflow_get_values(&mask->mf)) * 8); + /* 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 = count_1bits(pkt_bits_u0); + const uint64_t pkt_bits_u1 = key->mf.map.bits[1]; + + /* Unit 0 flattening */ + netdev_flow_key_flatten_unit(&pkt_blocks[0], + &tbl_blocks[0], + &mf_masks[0], + &blocks_scratch[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 blocks_scratch 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], + &blocks_scratch[u0_count], + pkt_bits_u1, + u1_count); } -uint32_t -dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable, - uint32_t keys_map, - const struct netdev_flow_key *keys[], - struct dpcls_rule **rules) +/* Compares a rule and the blocks representing a key, returns 1 on a match. */ +static inline uint64_t +netdev_rule_matches_key(const struct dpcls_rule *rule, + const uint32_t mf_bits_total, + const uint64_t *blocks_scratch) { - int i; - uint32_t found_map; + const uint64_t *keyp = miniflow_get_values(&rule->flow.mf); + const uint64_t *maskp = miniflow_get_values(&rule->mask->mf); + uint64_t not_match = 0; + + for (int i = 0; i < mf_bits_total; i++) { + not_match |= (blocks_scratch[i] & maskp[i]) != keyp[i]; + } - /* Compute hashes for the remaining keys. Each search-key is - * masked with the subtable's mask to avoid hashing the wildcarded - * bits. */ + /* 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. + * + * Note: this function is marked with ALWAYS_INLINE to ensure the compiler + * inlines the below code, and then uses the compile time constants to make + * specialized versions of the runtime code. Without ALWAYS_INLINE, the + * compiler might decide to not inline, and performance will suffer. + */ +static inline uint32_t ALWAYS_INLINE +lookup_generic_impl(struct dpcls_subtable *subtable, + uint64_t *blocks_scratch, + 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 n_pkts = count_1bits(keys_map); + ovs_assert(NETDEV_MAX_BURST >= n_pkts); uint32_t hashes[NETDEV_MAX_BURST]; + + const uint32_t bit_count_total = bit_count_u0 + bit_count_u1; + uint64_t *mf_masks = subtable->mf_masks; + int i; + + /* Flatten the packet metadata into the blocks_scratch[] using subtable. */ + ULLONG_FOR_EACH_1 (i, keys_map) { + netdev_flow_key_flatten(keys[i], + &subtable->mask, + mf_masks, + &blocks_scratch[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) { - hashes[i] = netdev_flow_key_hash_in_mask(keys[i], &subtable->mask); + uint64_t *block_ptr = &blocks_scratch[i * bit_count_total]; + uint32_t hash = hash_add_words64(0, block_ptr, bit_count_total); + hashes[i] = hash_finish(hash, bit_count_total * 8); } - /* Lookup. */ + /* 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); - /* 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. */ + /* 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]) { - if (OVS_LIKELY(dpcls_rule_matches_key(rule, keys[i]))) { + const uint32_t cidx = i * bit_count_total; + uint32_t match = netdev_rule_matches_key(rule, bit_count_total, + &blocks_scratch[cidx]); + + if (OVS_LIKELY(match)) { rules[i] = rule; - /* Even at 20 Mpps the 32-bit hit_cnt cannot wrap - * within one second optimization interval. */ subtable->hit_cnt++; goto next; } @@ -96,3 +224,16 @@ dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable, return found_map; } + +/* Generic lookup function that uses runtime provided mf bits for iterating. */ +uint32_t +dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable, + uint64_t *blocks_scratch, + uint32_t keys_map, + const struct netdev_flow_key *keys[], + struct dpcls_rule **rules) +{ + return lookup_generic_impl(subtable, blocks_scratch, keys_map, keys, rules, + subtable->mf_bits_set_unit0, + subtable->mf_bits_set_unit1); +} diff --git a/lib/dpif-netdev-private.h b/lib/dpif-netdev-private.h index 555856482..e1ceaa641 100644 --- a/lib/dpif-netdev-private.h +++ b/lib/dpif-netdev-private.h @@ -56,13 +56,15 @@ struct dpcls_rule { */ typedef uint32_t (*dpcls_subtable_lookup_func)(struct dpcls_subtable *subtable, + uint64_t *blocks_scratch, uint32_t keys_map, const struct netdev_flow_key *keys[], struct dpcls_rule **rules); -/* Prototype for generic lookup func, using same code path as before. */ +/* Prototype for generic lookup func, using generic scalar code path. */ uint32_t dpcls_subtable_lookup_generic(struct dpcls_subtable *subtable, + uint64_t *blocks_scratch, uint32_t keys_map, const struct netdev_flow_key *keys[], struct dpcls_rule **rules); @@ -77,12 +79,22 @@ struct dpcls_subtable { uint32_t hit_cnt; /* Number of match hits in subtable in current optimization interval. */ + /* Miniflow fingerprint that the 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; + /* Caches the masks to match a packet to, reducing runtime calculations. */ + uint64_t *mf_masks; + struct netdev_flow_key mask; /* Wildcards for fields (const). */ /* 'mask' must be the last field, additional space is allocated here. */ }; diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c index b42ca35e3..1b92cd4c9 100644 --- a/lib/dpif-netdev.c +++ b/lib/dpif-netdev.c @@ -233,6 +233,15 @@ struct dpcls { odp_port_t in_port; struct cmap subtables_map; struct pvector subtables; + + /* Region of memory for this DPCLS instance to use as scratch. + * Size is guaranteed to be large enough to hold all blocks required for + * the subtable's to match on. This allows each dpcls lookup to flatten + * the packet miniflows into this blocks_scratch area, without using + * variable length arrays. This region is allocated on subtable create, and + * will be resized as required if a larger subtable is added. */ + uint64_t *blocks_scratch; + uint32_t blocks_scratch_size; }; /* Data structure to keep packet order till fastpath processing. */ @@ -7649,6 +7658,7 @@ static void dpcls_subtable_destroy_cb(struct dpcls_subtable *subtable) { cmap_destroy(&subtable->rules); + ovsrcu_postpone(free, subtable->mf_masks); ovsrcu_postpone(free, subtable); } @@ -7659,6 +7669,8 @@ dpcls_init(struct dpcls *cls) { cmap_init(&cls->subtables_map); pvector_init(&cls->subtables); + cls->blocks_scratch = NULL; + cls->blocks_scratch_size = 0; } static void @@ -7686,6 +7698,7 @@ dpcls_destroy(struct dpcls *cls) } cmap_destroy(&cls->subtables_map); pvector_destroy(&cls->subtables); + ovsrcu_postpone(free, cls->blocks_scratch); } } @@ -7701,7 +7714,28 @@ 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. */ + /* The count of bits in the mask defines the space required for masks. + * Then call gen_masks() to create the appropriate masks, avoiding the cost + * of doing runtime calculations. */ + uint32_t unit0 = count_1bits(mask->mf.map.bits[0]); + uint32_t unit1 = count_1bits(mask->mf.map.bits[1]); + subtable->mf_bits_set_unit0 = unit0; + subtable->mf_bits_set_unit1 = unit1; + + subtable->mf_masks = xmalloc(sizeof(uint64_t) * (unit0 + unit1)); + netdev_flow_key_gen_masks(mask, subtable->mf_masks, unit0, unit1); + + /* Allocate blocks scratch space only if subtable requires more size than + * is currently allocated. */ + const uint32_t blocks_required_per_pkt = unit0 + unit1; + if (cls->blocks_scratch_size < blocks_required_per_pkt) { + free(cls->blocks_scratch); + cls->blocks_scratch = xmalloc(sizeof(uint64_t) * NETDEV_MAX_BURST * + blocks_required_per_pkt); + cls->blocks_scratch_size = blocks_required_per_pkt; + } + + /* Assign the generic lookup - this works with any miniflow fingerprint. */ subtable->lookup_func = dpcls_subtable_lookup_generic; cmap_insert(&cls->subtables_map, &subtable->cmap_node, mask->hash); @@ -7846,6 +7880,43 @@ dpcls_remove(struct dpcls *cls, struct dpcls_rule *rule) } } +/* 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 replaces runtime-calculating the masks. + * @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 + */ +void +netdev_flow_key_gen_masks(const struct netdev_flow_key *tbl, + uint64_t *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]); +} + /* Returns true if 'target' satisfies 'key' in 'mask', that is, if each 1-bit * in 'mask' the values in 'key' and 'target' are the same. */ bool @@ -7886,6 +7957,7 @@ dpcls_lookup(struct dpcls *cls, const struct netdev_flow_key *keys[], BUILD_ASSERT_DECL(MAP_BITS >= NETDEV_MAX_BURST); struct dpcls_subtable *subtable; + uint64_t *blocks_scratch = cls->blocks_scratch; uint32_t keys_map = TYPE_MAXIMUM(uint32_t); /* Set all bits. */ @@ -7906,7 +7978,8 @@ dpcls_lookup(struct dpcls *cls, const struct netdev_flow_key *keys[], * non-overlapping. */ PVECTOR_FOR_EACH (subtable, &cls->subtables) { /* Call the subtable specific lookup function. */ - found_map = subtable->lookup_func(subtable, keys_map, keys, rules); + found_map = subtable->lookup_func(subtable, blocks_scratch, keys_map, + keys, rules); /* Count the number of subtables searched for this packet match. This * estimates the "spread" of subtables looked at per matched packet. */ -- 2.17.1 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev