STRUCT MEMORY_GROUP(9)

💖 struct memory_group(9) 💖

okay so bestie, welcome to the Kernel API Manual page for struct memory_group and honestly? it's giving "the group chat that keeps your memory blocks organized" ✨ let's get into it 🫶

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🌸 NAME 🌸

struct memory_group — a logical group of memory blocks 🎀

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🦋 SYNOPSIS 🦋

here's the whole lil struct, copy it exactly bestie, no typos:

struct memory_group {
    int nid;
    struct list_head memory_blocks;
    unsigned long present_kernel_pages;
    unsigned long present_movable_pages;
    bool is_dynamic;
    union {
      struct {
        unsigned long max_pages;
      } s;
      struct {
        unsigned long unit_pages;
      } d;
    };
 };

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⭐ Members ⭐

• nid — the node id for all the memory blocks hanging out inside this memory group 🔥 like, every single one of them, same node, no exceptions.
• memory_blocks — a list of all the memory blocks that belong to this memory group 💅 it's the membership roster, fr fr.
• present_kernel_pages — present (online) memory outside ZONE_MOVABLE of this memory group 👑 so: the not-squishy part.
• present_movable_pages — present (online) memory in ZONE_MOVABLE of this memory group 🧚 the movable besties.
• is_dynamic — the memory group type, i.e. static vs. dynamic 🦋 this one decides which half of the union you're allowed to love.
• {unnamed_union} — anonymous 🙈 it's an anonymous union, it has no name, it simply is. main character energy tbh.
• s.max_pages — valid only when memory_group.is_dynamic == false ⭐ it's the maximum number of pages we'll have in this static memory group.
• d.unit_pages — valid only when memory_group.is_dynamic == true 💜 the unit, in pages, in which memory is added/removed in this dynamic memory group. this granularity defines the alignment of a unit in physical address space, and ngl it has to be at least as big as a single memory block 🌈 (not me stressing this, but like, it is a requirement).

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✨ Description ✨

so a memory group logically groups memory blocks together 💫 and each memory block belongs to at most one memory group — no double-dipping, we don't do that here 🙅‍♀️

a memory group corresponds to a memory device, like a DIMM or a NUMA node, which spans multiple memory blocks and might even span multiple non-contiguous physical memory ranges 😭 iconic behavior honestly.

modification of members after registration is serialized by memory hot(un)plug code 🔒 so pls don't just go poking at it from anywhere, iykyk.

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💀 SEE ALSO 💀

• Kernel file ./include/linux/memory.h
• memory_block_aligned_range(9)

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that's the whole page bestie, you ate 💅

this lil gem lives in ./include/linux and it's dated October 2026 — so mark your calendar, mwah 🎀💖✨