memblock_alloc_internal(9)

📦 version 7.3.1, in nixpkgs unstable

💖 memblock_alloc_internal(9) — allocate boot memory block 💖

okay so bestie, welcome to the Kernel API Manual, and buckle up because today we're learning about memblock_alloc_internal, which is genuinely one of those functions that does exactly what it says on the tin: it allocates a boot memory block. iconic behaviour, no notes, we love a self-explanatory name ✨

🎀 SYNOPSIS 🎀

void * memblock_alloc_internal (phys_addr_t size , phys_addr_t align ,
phys_addr_t min_addr , phys_addr_t max_addr , int nid , bool exact_nid
);

like. look at all those parameters. she's got range 💅

🌸 ARGUMENTS 🌸

  • size — the size of the memory block you wanna allocate, in bytes. yes bytes. yes it matters. don't @ me 💖
  • align — the alignment of the region and of the block's size. both. at the same time. she's doing the most and honestly? slay.
  • min_addr — the lower bound of the memory region you're allocating from (a physical address, iykyk).
  • max_addr — the upper bound of the memory region you're allocating from (also a physical address, fr fr).
  • nid — the nid of the free area to look for. or like, if you literally don't care which node, you pass NUMA_NO_NODE and vibe 😌
  • exact_nid — controls whether the allocation is allowed to fall back to other nodes. so like, the "are we being picky or not" switch 🦋

✨ DESCRIPTION ✨

so basically here's the tea 🍓: this function allocates a memory block using memblock_alloc_range_nid, and then it takes the physical address that comes back and converts it to a virtual one. glow-up transformation moment, honestly 🔥

and now for the spicy part 🌶️ — the min_addr limit gets dropped if it can't be satisfied, and the allocation will just fall back to memory below min_addr. so like, she tried, she really did, but she's flexible 💀

the other constraints though — stuff like node and mirrored memory — those get handled again inside memblock_alloc_range_nid. so nothing's slipping through the cracks, bestie. double-checked and everything 👑

💜 RETURN 💜

  • On success? you get the virtual address of the allocated memory block. 🥳
  • On failure? NULL. 😭 it's giving "we don't have the memory for this rn".

🦋 SEE ALSO 🦋

okay this section is a whole friend group, so let's do roll call 🫶 starting with the source file and the big-picture overview:

that's the whole squad, every single one of them, no cap 🌈

ngl bestie, the min_addr fallback is the one thing to actually remember here — she will go below your lower bound if she has to. not a bug, just her being resourceful 💅

and that's the page!! this one came out of ./mm in October 2026, brought to you by the Kernel API Manual — mwah, ilysm, go allocate something responsibly 💖🎀🦋🌸

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