hash: add XXH3 to list of hash algorithms.

needs more testing. in a "pure miss" test to help show hashing overhead,
with four worker threads and large ascii multigets there is a measurable
performance boost for longer keys. Very short keys (10-15 bytes) are
about even.

for 150ish byte keys 12m rps -> 13m rps roughly. Not too bad!

need to test hash table distribution for large sets of keys before
merging. need to consider if worth switching the defaults now or later.

1 files changed, 10 insertions, 0 deletions

diff --git a/hash.c b/hash.c
index b5ff28a..ede1cce 100644
--- a/hash.c
+++ b/hash.c
@@ -3,9 +3,15 @@
 #include "memcached.h"
 #include "jenkins_hash.h"
 #include "murmur3_hash.h"
+#define XXH_INLINE_ALL // modifier for xxh3's include below
+#include "xxhash.h"
 
 hash_func hash;
 
+static uint32_t XXH3_hash(const void *key, size_t length) {
+    return (uint32_t)XXH3_64bits(key, length);
+}
+
 int hash_init(enum hashfunc_type type) {
     switch(type) {
         case JENKINS_HASH:
@@ -16,6 +22,10 @@ int hash_init(enum hashfunc_type type) {
             hash = MurmurHash3_x86_32;
             settings.hash_algorithm = "murmur3";
             break;
+        case XXH3_HASH:
+            hash = XXH3_hash;
+            settings.hash_algorithm = "xxh3";
+            break;
         default:
             return -1;
     }