The issue is that zeroing pages in the background is a pessimization, that should not ever be done. The user-mode program that allocates some memory is typicall

The issue is that zeroing pages in the background is a pessimization, that should not ever be done. The user-mode program that allocates some memory is typically not going to be able to use only writes that allocate new cache lines without reading memory. So to compare the two systems: Your system: memory is released, kernel clears it in the background, wasting write bandwidth (which might not matter for anything except power if the system was idle at the time), and when the user-mode program starts using it, it will start writing and every new line they write to will trigger a spurious read. Modern Linux: memory is released, kernel lets it lie, not using any power or bandwidth to do anything to it, until an user-mode program allocates it and touches the page. Then the kernel picks up the page, writes the entire page with 0:es using whatever idiom on that CPU allows it to just allocate the page in cache without reading it from the RAM. This is really fast, faster than a single memory fetch. The user-mode program can then directly use it without having to fetch anything from DRAM.