PR_SET_THP_DISABLE(2const)

💖 PR_SET_THP_DISABLE — from the Linux man-pages club 💖

okay bestie, so this one is PR_SET_THP_DISABLE, a <prctl> constant situation (it's a 2const page, iykyk) — basically it's the little switch that flips the state of the "THP disable" flags for the calling thread. yes that's the calling thread, not the whole world. 👑

🌸 LIBRARY 🌸

Standard C library (libc, -lc) — the usual queen.

✨ SYNOPSIS ✨

#include <linux/prctl.h>  /* Definition of PR_* constants */
#include <sys/prctl.h>

int prctl(PR_SET_THP_DISABLE, long thp_disable, unsigned long flags,
          0L, 0L);

like, that's the whole summoning ritual 🫶

🦋 DESCRIPTION 🦋

So what it does: it sets the state of the "THP disable" flags for the calling thread. If thp_disable has a nonzero value, the THP disable flag gets set according to whatever flags says. Otherwise, it gets cleared. simple as that, no cap. 💅

This prctl(2) is literally the method for disabling transparent huge pages for jobs where the code cannot be modified, and where using a malloc(3) hook with madvise(2) is not an option (i.e., statically allocated data). so like… it's giving "I can't touch the source, but I still want my pages small." 🙈

Also important: the setting of the "THP disable" flags is inherited by a child created via fork(2), and it is preserved across execve(2). it travels. it stays. main character energy. 👑

The behavior depends on the value of flags:

• 0 — the prctl(2) call will disable THPs completely for the process, irrespective of global THP controls or MADV_COLLAPSE. full send, no exceptions, periodt. 💀
• PR_THP_DISABLE_EXCEPT_ADVISED — the prctl(2) call will disable THPs for the process except when the usage of THPs is advised. Consequently, THPs will only be used when:
  • Global THP controls are set to "always" or "madvise" and madvise(..., MADV_HUGEPAGE) or madvise(..., MADV_COLLAPSE) is used.
  • Global THP controls are set to "never" and madvise(..., MADV_COLLAPSE) is used. This is the same behavior as if THPs would not be disabled on a process level.

so it's lowkey selective — THPs can still slide in, but only when they've been formally invited. 💌

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🎀 RETURN VALUE 🎀

On success, 0 is returned. On error, -1 is returned, and errno is set to indicate the error. so check your errno, bestie, don't just assume. 😭

🌈 STANDARDS 🌈

Linux. that's it, that's the answer. 🐧

⭐ HISTORY ⭐

Linux 3.15. vintage but thriving, honestly.

💜 SEE ALSO 💜

• prctl(2)
• PR_GET_THP_DISABLE(2const) — go read the sibling, they're a duo fr fr 🫶

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k bye, this page came from Linux man-pages 6.20, dated 2026-02-08, and yes it's giving blessed. slay, happy hacking, don't forget to prctl responsibly. 💖✨🌸🦋