What is the default user/kernel split in the 64bit linux ?

I read Documentation/x86_64/mm.txt (which someone pointed out), but I could not make out. Can somebody provide a direct answer (something like 3GB/1GB for 32bit implementation).

  • Do you mean the split for memory?
    – Kevin
    Commented Feb 21, 2012 at 15:29
  • @Kevin Yes. I meant the split of the memory.
    – Kris srini
    Commented Feb 22, 2012 at 6:11

1 Answer 1


Like the docs say, user space gets 247 bytes = 128TiB, and kernel gets 512MiB. The rest of the address space goes to various parts of the system, along with a few unusable holes.

  • 64bit kernel gets less memory than 32bit, why?
    – Ted
    Commented Jun 21, 2022 at 8:07

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