Does mmap with MAP_NORESERVE reserve physical memory?

Question

The mmap documentation says following about the flag MAP_NORESERVE.

Do not reserve swap space for this mapping. When swap space is reserved, one ha

Answer 1

On linux mmap sets up virtual memory mappings only, whether you use MAP_NORESERVE or not, no physical memory is assigned until you touch the memory.

MAP_FIXED is unrelated to this, it sets up the virtual memory mappings at the virtual(not physical) address you specify, or fails if there's no room for the mapping at that address.