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Does mmap with MAP_NORESERVE have backup physical memory?

The mmap documentation contains the following information about the MAP_NORESERVE flag.

Do not reserve swap space for this mapping. When the swap space is reserved, one has a guarantee that the display can be changed. When the swap space is not reserved, you can get SIGSEGV on write if physical memory is not available.

In reality, I only want to reserve virtual memory addresses and not allocate actual physical memory. Can this be done using mmap with MAP_NORESERVE? If I want to use some kind of physical memory, I would simulate it again using MAP_FIXED in a range of addresses within one located through mmap with MAP_NORESERVE.

To summarize, I want the kernel not to reserve any physical page for memory allocated using mmap with the flag MAP_NORSERVE. Does it really work that way or does the kernel allocate physical pages if it has enough physical memory?

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Mmap () is one way to manage the relationship between {address, physical memory, disk blocks}. All three members of this association are resources. The link is stored inside page table entries (PTE)

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