Function TouchArea

cpp/src/arrow/memory_pool_benchmark.cc:65–78

Benchmark the cost of accessing always the same memory area. This gives us a lower bound of the potential difference between AllocateTouchDeallocate and AllocateDeallocate.

// This gives us a lower bound of the potential difference between
// AllocateTouchDeallocate and AllocateDeallocate.
static void TouchArea(benchmark::State& state) {  // NOLINT non-const reference
  const int64_t nbytes = state.range(0);
  MemoryPool* pool = default_memory_pool();
  uint8_t* data;
  ARROW_CHECK_OK(pool->Allocate(nbytes, &data));

  for (auto _ : state) {
    TouchCacheLines(data, nbytes);
  }

  pool->Free(data, nbytes);
  state.SetItemsProcessed(state.iterations());
  state.SetBytesProcessed(state.iterations() * nbytes);
}

// Benchmark the raw cost of allocating memory.
// Note this is a best case situation: we always allocate and deallocate exactly