tests: Introduce perf_hash.cc, hashing benchmark

Output on my laptop:

$ build/release/tests/perf/perf_hash
Timing fixed hash...
28671657.15 tps
28720930.45 tps
28622017.20 tps
28677088.01 tps
29223543.70 tps
Timing iterator hash...
22023042.57 tps
21953352.04 tps
21393787.05 tps
21613837.10 tps
21563284.57 tps

configure.py

@@ -158,6 +158,7 @@ urchin_tests = [
     'tests/urchin/types_test',
     'tests/urchin/keys_test',
     'tests/perf/perf_mutation',
+    'tests/perf/perf_hash',
     'tests/perf/perf_cql_parser',
     'tests/perf/perf_simple_query',
     'tests/urchin/cql_query_test',

tests/perf/perf_hash.cc

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2015 Cloudius Systems
+ */
+
+#include "utils/murmur_hash.hh"
+#include "tests/perf/perf.hh"
+
+volatile uint64_t black_hole;
+
+int main(int argc, char* argv[]) {
+    const uint64_t seed = 0;
+    auto src = bytes("0123412308129301923019283056789012345");
+
+    uint64_t sink = 0;
+
+    std::cout << "Timing fixed hash...\n";
+
+    time_it([&] {
+        std::array<uint64_t,2> dst;
+        utils::murmur_hash::hash3_x64_128(src, seed, dst);
+        sink += dst[0];
+        sink += dst[1];
+    });
+
+    std::cout << "Timing iterator hash...\n";
+
+    time_it([&] {
+        std::array<uint64_t,2> dst;
+        utils::murmur_hash::hash3_x64_128(src.begin(), src.size(), seed, dst);
+        sink += dst[0];
+        sink += dst[1];
+    });
+
+    black_hole = sink;
+}