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It'll probably be quite a while before operating systems rush to turn on extra level of page walk fun, increasing TLB miss penalty even more.

If only x86 could have 64 kB pages...

Of course you're right it's not a great idea to use those bits. Eventually they will be in use, although it's probably 10+ years.

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The linux kernel has patches for it submitted now, ready for when the hardware arrives https://www.phoronix.com/scan.php?page=news_item&px=Linux-De...

My point was that very few need more than 48 bits of virtual address space. Having extra layer of lookup will reduce page walk performance.

52-bit physical & 57-bit virtual address space is a no brainer if you have more than 128 TB of RAM installed, of course. :-)

Isn't the tendency to use more and more large pages (1MiB) on x86 anyway? And then just use user space allocators to split them up for malloc.

x86 large pages are 2 MB (64-bit) or 4 MB (32-bit). Even larger page variety is 1 GB. They do save a lot of TLB misses, but can be painful to reliably allocate.

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