On 15.07.2019 19:36, Harry van Haaren wrote: > 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> > > --- > > 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 | 214 +++++++++++++++++++++++++------ > lib/dpif-netdev-private.h | 8 +- > lib/dpif-netdev.c | 77 ++++++++++- > 3 files changed, 258 insertions(+), 41 deletions(-) > > diff --git a/lib/dpif-netdev-lookup-generic.c > b/lib/dpif-netdev-lookup-generic.c > index 833abf54f..abd166fc3 100644 > --- a/lib/dpif-netdev-lookup-generic.c > +++ b/lib/dpif-netdev-lookup-generic.c > @@ -30,68 +30,210 @@ > #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);
dpif_netdev_lookup_generic? BTW, this might be not needed if we'll remove logging in the patch #5. > + > +/* 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 */ Missed comment (style). > + 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; > } > } > - /* 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. */ > + > + /* 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. */ > + ; /* Keep Sparse happy. */ You're changing the indentation of this comment back and forth few times around the patch series. > } > > 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 b235e23c8..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); > @@ -84,13 +86,13 @@ struct dpcls_subtable { > 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 > + /* 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 > */ > + /* Caches the masks to match a packet to, reducing runtime calculations. > */ Above two changes should be part of the previous patches. BTW, introduction of the 'mf_masks' and 'mf_bits*' should happen in this patch, not in the "dpif-netdev: Move dpcls lookup structures to .h". > uint64_t *mf_masks; > > struct netdev_flow_key mask; /* Wildcards for fields (const). */ > diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c > index b42ca35e3..8acc1445a 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 garaunteed to be large enough to hold all blocks required for s/garaunteed/guaranteed/ > + * the subtable's to match on. This allows each dpcls lookup to flatten > + * the packet miniflows into this blocks_scratch area, without using > + * variable lenght arrays. This region is allocated on subtable create, > and s/lenght/length/ > + * 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. > */ > _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev