Deallocation code path performance - test hash function

Re-test the collision rate of the hash we use.
DataDog · Sep 8, 2023 · 167264f · 167264f
1 parent e5797c5
commit 167264f
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/test/address_bitset-ut.cc b/test/address_bitset-ut.cc
@@ -42,13 +42,20 @@ TEST(address_bitset, many_addresses) {
   EXPECT_EQ(0, address_bitset.nb_addresses());
 }
 
-// This test is mostly to tune the hash approach (it would slow down CI)
+// This test to tune the hash approach
+// Collision rate is around 5.7%, which will have an impact on sampling
+//#define COLLISION_TEST
 #ifdef COLLISION_TEST
 // Your hash function
 #  ifdef TEST_IDENTITY
 inline uint64_t my_hash(uintptr_t h1) { return h1; }
 #  else
-inline uint64_t my_hash(uintptr_t h1) { return h1 >> 8; }
+inline uint64_t my_hash(uintptr_t h1) {
+  h1 = h1 >> 4;
+  uint32_t high = (uint32_t)(h1 >> 32);
+  uint32_t low = (uint32_t)h1;
+  return high ^ low;
+}
 #  endif
 
 TEST(address_bitset, hash_function) {