touch_pmd(9)

💅 touch_pmd(9) — like, the whole manual page, bestie

okay so this is touch_pmd, straight out of the Kernel API Manual (yes, the manpage name is literally the function name, we love a self-titled era). It's a kernel function, it deals with page tables, and honestly? It's giving "small function, big responsibilities." Let's get into it 🎀

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✨ NAME ✨

touch_pmd — mark the page table pmd entry as accessed and dirty (for write). That's it, that's the whole vibe. It's touching the pmd. Respectfully. 🫶

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🌸 SYNOPSIS 🌸

bool touch_pmd (struct vm_area_struct *vma , unsigned long addr , pmd_t
*pmd , bool write );

She takes four args and returns a bool. Iconic signature, no notes. ✨

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🦋 ARGUMENTS 🦋

• vma — the VMA that's covering addr. Like, the neighborhood this address lives in 💖
• addr — the virtual address itself. The main character, literally 📍
• pmd — a pmd pointer into the page table that maps addr. Yes it's a pointer to a pointer-ish situation, we're in page table land now 🧚
• write — whether this is a write access. So like, are we writing or just looking 👀

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🔥 RETURN 🔥

It returns whether the pmd entry is changed — so true if it got touched/changed, and not-that if it didn't. No cap, that's the whole answer. 💅

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🌈 SEE ALSO 🌈

All the friends in the group chat, all in the kernel file ./mm/huge_memory.c:

• vmf_insert_pfn_pmd(9)
• vmf_insert_pfn_pud(9)
• vmf_insert_folio_pud(9)
• zap_huge_pmd(9)
• __split_unmapped_folio(9)
• folio_check_splittable(9)
• __folio_split(9)
• folio_split_unmapped(9)
• folio_split(9)
• min_order_for_split(9)

Go read those too, iykyk 📚✨

lowkey a reminder: these are cross-references, not extra behaviour — don't go assuming stuff about touch_pmd just because its friends do other things 🙈

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aaaand that's the page!! shoutout to the ./mm corner of the tree for hosting all this, dated October 2026 — mark your calendars bestie, the source is ./mm and the date is October 2026, and that's the cute little sign-off 💖🎀 see u in the next manpage, mwah 🫶