Create and destroy tables outside of the timer and in batch in Reserve benchmarks.

PiperOrigin-RevId: 592483250
Change-Id: I55fa9982c4dbc723b30957cb31da95251e368707

absl/container/internal/raw_hash_set_benchmark.cc

@@ -387,28 +387,42 @@ void BM_NoOpReserveStringTable(benchmark::State& state) {
 BENCHMARK(BM_NoOpReserveStringTable);
 
 void BM_ReserveIntTable(benchmark::State& state) {
-  int reserve_size = state.range(0);
-  for (auto _ : state) {
+  constexpr size_t kBatchSize = 1024;
+  size_t reserve_size = static_cast<size_t>(state.range(0));
+
+  std::vector<IntTable> tables;
+  while (state.KeepRunningBatch(kBatchSize)) {
     state.PauseTiming();
-    IntTable t;
+    tables.clear();
+    tables.resize(kBatchSize);
     state.ResumeTiming();
+    for (auto& t : tables) {
       benchmark::DoNotOptimize(t);
       t.reserve(reserve_size);
+      benchmark::DoNotOptimize(t);
+    }
   }
 }
-BENCHMARK(BM_ReserveIntTable)->Range(128, 4096);
+BENCHMARK(BM_ReserveIntTable)->Range(1, 64);
 
 void BM_ReserveStringTable(benchmark::State& state) {
-  int reserve_size = state.range(0);
-  for (auto _ : state) {
+  constexpr size_t kBatchSize = 1024;
+  size_t reserve_size = static_cast<size_t>(state.range(0));
+
+  std::vector<StringTable> tables;
+  while (state.KeepRunningBatch(kBatchSize)) {
     state.PauseTiming();
-    StringTable t;
+    tables.clear();
+    tables.resize(kBatchSize);
     state.ResumeTiming();
+    for (auto& t : tables) {
       benchmark::DoNotOptimize(t);
       t.reserve(reserve_size);
+      benchmark::DoNotOptimize(t);
+    }
   }
 }
-BENCHMARK(BM_ReserveStringTable)->Range(128, 4096);
+BENCHMARK(BM_ReserveStringTable)->Range(1, 64);
 
 // Like std::iota, except that ctrl_t doesn't support operator++.
 template <typename CtrlIter>