LIBUVMEM(3)

💖 LIBUVMEM(3) — like, the userspace resource allocator era 💖

okay bestie, quick vibe check: this is libuvmem(3) from the Library Functions Manual section, and she is literally the userspace glow-up of a kernel icon. let's get into it 🫶

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✨ NAME ✨

libuvmem — the userspace general purpose resource allocator 💅 (yes, general purpose, yes, resource allocator, no she's not just for one lil thing)

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🌸 SYNOPSIS 🌸

library “libuvmem”
#include <sys/vmem.h>

so you link the library named libuvmem and you pull in <sys/vmem.h> — that's the whole entry ritual, no cap 🎀

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🦋 DESCRIPTION 🦋

so libuvmem is a general purpose resource allocator. that's the whole personality.

it's a port of the kernel facility of the similar name, vmem — like, the userspace sister of the kernel one, same energy, different address space 💫

and for the actual documentation? bestie, go read the description of the kernel allocator vmem(9). that's where the docs live. i'm not gonna reinvent the wheel when the icon already did it 👑

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👑 NOTES 👑

okay this is the part where i tell you the things you need to know so you don't get got 🙈

• the “quantum cache” feature is not implemented for userspace. so the quantum and qcache_max arguments of the vmem_create() function are ignored. like, they're there, they're cute, they do nothing. don't @ me 💀
• the library internally uses malloc(3) to allocate the structures that track allocations. so yeah, that's the plumbing under the glitter ✨
• the allocator is thread-safe. periodt. and the locks for separate vmem's are independent between each other — so one busy vmem isn't out here blocking another one's whole flop era 🧚
• the supported flags for the vmem_xalloc() function are:
  • M_NOWAIT
  • M_FIRSTFIT
  • M_BESTFIT
  • M_NEXTFIT

those four. that's the list. don't come at her with anything else 🍓

real talk though: those flags only exist for vmem_xalloc() — so if you're passing them somewhere else and expecting magic, that's a you problem, not a libuvmem problem 💀

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🌈 AUTHORS 🌈

for the history of the kernel allocator, go see vmem(9) — she has lore 💜

the userspace port for FreeBSD was done by Konstantin Belousov <kib@FreeBSD.org>. shoutout, king 👑✨

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and that's the page, bestie! 🎀 this lil writeup came from the Debian edition, dated October 16, 2025, and it's LIBUVMEM(3) — go forth and allocate, responsibly 💖🦋