&gt; calloc itself calls memset in user space.<p>Have you considered reading my comment past the first phrase? If you don&#x27;t actually touch the page, the system <i>doesn&#x27;t need to allocate it</i>, let alone zero it. If you don&#x27;t touch the page, assuming you&#x27;re benching on linux you&#x27;re measuring the cost of mapping a preexisting zeroed COW page, not the cost of actually allocating that memory.