[dpdk-dev] [PATCH v3 3/4] hash: add vectorized comparison

[Pablo de Lara]

From: Byron Marohn <byron.marohn at intel.com>

In lookup bulk function, the signatures of all entries
are compared against the signature of the key that is being looked up.
Now that all the signatures are together, they can be compared
with vector instructions (SSE, AVX2), achieving higher lookup performance.

Also, entries per bucket are increased to 8 when using processors
with AVX2, as 256 bits can be compared at once, which is the size of
8x32-bit signatures.

Signed-off-by: Byron Marohn <byron.marohn at intel.com>
Signed-off-by: Saikrishna Edupuganti <saikrishna.edupuganti at intel.com>
Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
---
 lib/librte_hash/rte_cuckoo_hash.c | 73 ++++++++++++++++++++++++++++++++++++---
 lib/librte_hash/rte_cuckoo_hash.h | 12 ++++++-
 2 files changed, 79 insertions(+), 6 deletions(-)

diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index 9d507b6..eab28a1 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -283,6 +283,15 @@ rte_hash_create(const struct rte_hash_parameters *params)
 	h->free_slots = r;
 	h->hw_trans_mem_support = hw_trans_mem_support;
 
+#if defined(RTE_ARCH_X86)
+	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_AVX2))
+		h->sig_cmp_fn = RTE_HASH_COMPARE_AVX2;
+	else if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE2))
+		h->sig_cmp_fn = RTE_HASH_COMPARE_SSE;
+	else
+#endif
+		h->sig_cmp_fn = RTE_HASH_COMPARE_SCALAR;
+
 	/* Turn on multi-writer only with explicit flat from user and TM
 	 * support.
 	 */
@@ -939,6 +948,61 @@ lookup_stage1(unsigned idx, hash_sig_t *prim_hash, hash_sig_t *sec_hash,
 	rte_prefetch0(*secondary_bkt);
 }
 
+static inline void
+compare_signatures(unsigned *prim_hash_matches, unsigned *sec_hash_matches,
+				const struct rte_hash_bucket *prim_bkt,
+				const struct rte_hash_bucket *sec_bkt,
+				hash_sig_t prim_hash, hash_sig_t sec_hash,
+				enum rte_hash_sig_compare_function sig_cmp_fn)
+{
+	unsigned i;
+
+	switch (sig_cmp_fn) {
+#ifdef RTE_MACHINE_CPUFLAG_AVX2
+	case RTE_HASH_COMPARE_AVX2:
+		*prim_hash_matches |= _mm256_movemask_ps((__m256)_mm256_cmpeq_epi32(
+				_mm256_load_si256(
+					(__m256i const *)prim_bkt->sig_current),
+				_mm256_set1_epi32(prim_hash)));
+		*sec_hash_matches |= _mm256_movemask_ps((__m256)_mm256_cmpeq_epi32(
+				_mm256_load_si256(
+					(__m256i const *)sec_bkt->sig_current),
+				_mm256_set1_epi32(sec_hash)));
+		break;
+#endif
+#ifdef RTE_MACHINE_CPUFLAG_SSE2
+	case RTE_HASH_COMPARE_SSE:
+		/* Compare the first 4 signatures in the bucket */
+		*prim_hash_matches |= _mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+				_mm_load_si128(
+					(__m128i const *)prim_bkt->sig_current),
+				_mm_set1_epi32(prim_hash)));
+		*prim_hash_matches |= (_mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+				_mm_load_si128(
+					(__m128i const *)&prim_bkt->sig_current[4]),
+				_mm_set1_epi32(prim_hash)))) << 4;
+		/* Compare the first 4 signatures in the bucket */
+		*sec_hash_matches |= _mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+				_mm_load_si128(
+					(__m128i const *)sec_bkt->sig_current),
+				_mm_set1_epi32(sec_hash)));
+		*sec_hash_matches |= (_mm_movemask_ps((__m128)_mm_cmpeq_epi16(
+				_mm_load_si128(
+					(__m128i const *)&sec_bkt->sig_current[4]),
+				_mm_set1_epi32(sec_hash)))) << 4;
+		break;
+#endif
+	default:
+		for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
+			*prim_hash_matches |=
+				((prim_hash == prim_bkt->sig_current[i]) << i);
+			*sec_hash_matches |=
+				((sec_hash == sec_bkt->sig_current[i]) << i);
+		}
+	}
+
+}
+
 /*
  * Lookup bulk stage 2:  Search for match hashes in primary/secondary locations
  * and prefetch first key slot
@@ -951,15 +1015,14 @@ lookup_stage2(unsigned idx, hash_sig_t prim_hash, hash_sig_t sec_hash,
 		uint64_t *extra_hits_mask, const void *keys,
 		const struct rte_hash *h)
 {
-	unsigned prim_hash_matches, sec_hash_matches, key_idx, i;
+	unsigned prim_hash_matches, sec_hash_matches, key_idx;
 	unsigned total_hash_matches;
 
 	prim_hash_matches = 1 << RTE_HASH_BUCKET_ENTRIES;
 	sec_hash_matches = 1 << RTE_HASH_BUCKET_ENTRIES;
-	for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
-		prim_hash_matches |= ((prim_hash == prim_bkt->sig_current[i]) << i);
-		sec_hash_matches |= ((sec_hash == sec_bkt->sig_current[i]) << i);
-	}
+
+	compare_signatures(&prim_hash_matches, &sec_hash_matches, prim_bkt,
+				sec_bkt, prim_hash, sec_hash, h->sig_cmp_fn);
 
 	key_idx = prim_bkt->key_idx[__builtin_ctzl(prim_hash_matches)];
 	if (key_idx == 0)
diff --git a/lib/librte_hash/rte_cuckoo_hash.h b/lib/librte_hash/rte_cuckoo_hash.h
index 86471f7..8ffc146 100644
--- a/lib/librte_hash/rte_cuckoo_hash.h
+++ b/lib/librte_hash/rte_cuckoo_hash.h
@@ -130,7 +130,7 @@ enum add_key_case {
 };
 
 /** Number of items per bucket. */
-#define RTE_HASH_BUCKET_ENTRIES		4
+#define RTE_HASH_BUCKET_ENTRIES		8
 
 #define NULL_SIGNATURE			0
 
@@ -161,6 +161,14 @@ struct rte_hash_key {
 	char key[0];
 } __attribute__((aligned(KEY_ALIGNMENT)));
 
+/* All different signature compare functions */
+enum rte_hash_sig_compare_function {
+	RTE_HASH_COMPARE_SCALAR = 0,
+	RTE_HASH_COMPARE_SSE,
+	RTE_HASH_COMPARE_AVX2,
+	RTE_HASH_COMPARE_NUM
+};
+
 /** Bucket structure */
 struct rte_hash_bucket {
 	hash_sig_t sig_current[RTE_HASH_BUCKET_ENTRIES];
@@ -183,6 +191,8 @@ struct rte_hash {
 	/**< Custom function used to compare keys. */
 	enum cmp_jump_table_case cmp_jump_table_idx;
 	/**< Indicates which compare function to use. */
+	enum rte_hash_sig_compare_function sig_cmp_fn;
+	/**< Indicates which signature compare function to use. */
 	uint32_t bucket_bitmask;        /**< Bitmask for getting bucket index
 						from hash signature. */
 	uint32_t key_entry_size;         /**< Size of each key entry. */
-- 
2.7.4