[rcxdude]

Note that the page file is essentially a datastructure which maps addresses to other addresses, but it also resides in the same physical memory. If you were to try to map every byte of a system to different physical address, it would need significantly more memory than the system had! Further, the datastructure needs to allow efficient lookup of data because the pagefile mapping occurs on every memory access (results are cached in the Translation Lookaside Buffer (TLB) and the speed and accuracy of this cache is often a limiting factor in the speed of the CPU). This all biases towards the mapping wanting to be quite coarse, in fact 4kB is probably already not optimal on today's systems with gigabytes of memory.

[notepad0x90]

But why does it work that way, why does all memory need to be mapped before allocation? why can't it work like file systems where you have a table/datastructure mapping inodes to files? The smaller your allocations are, the less total ram you have, that would make sense. Some apps need huge chunks of memory, some don't, why the one-size-fits-all approach? TLB lookup can also be O(n), it will be slower when you have lots of small allocations because that means lots of lookups but that lets applications optimize performance that way instead of having it be a system-wide setting.