alloc_pages_exact(9)

💅 alloc_pages_exact — the Kernel API Manual page you didn't know you needed

okay so this is alloc_pages_exact, straight out of the Kernel API Manual, and bestie, it's genuinely one of the more relatable ones: it does exactly what it says on the tin 🎀

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✨ NAME ✨

alloc_pages_exact — allocate an exact number of physically-contiguous pages. no rounding up, no extra baggage, we're being precise today 💅

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🦋 SYNOPSIS 🦋

void * alloc_pages_exact (size_t size , gfp_t gfp_mask );

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🌸 ARGUMENTS 🌸

• size — the number of bytes to allocate. like, the actual amount you want, not a vibe-based estimate 💖
• gfp_mask — the GFP flags for the allocation. must not contain __GFP_COMP. that's not a suggestion, that's a rule 🚫

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🔥 DESCRIPTION 🔥

so here's the tea: this function is similar to alloc_pages, except that it allocates the minimum number of pages to satisfy the request. that's the whole flex.

alloc_pages can only allocate memory in power-of-two pages. iconic but limiting, honestly. alloc_pages_exact said "not me being stuck with that" and just gives you what you asked for 🫶

it's also limited by MAX_PAGE_ORDER. so like, there is a ceiling, no cap (well, yes cap actually, but you get it).

⚠️ Memory allocated by this function must be released by free_pages_exact. don't just ghost it, bestie. that's a leak and it's not cute 😭

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⭐ RETURN ⭐

a pointer to the allocated area 🎀 or NULL in case of error 💀

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🌈 SEE ALSO 🌈

Kernel file ./mm/page_alloc.c, plus this whole squad:

• __get_pfnblock_flags_mask(9)
• get_pfnblock_bit(9)
• get_pfnblock_migratetype(9)
• __set_pfnblock_flags_mask(9)
• set_pfnblock_bit(9)
• clear_pfnblock_bit(9)
• set_pageblock_migratetype(9)
• __move_freepages_block_isolate(9)
• __putback_isolated_page(9)
• __free_pages(9)
• free_pages(9)
• alloc_pages_exact_nid(9)
• free_pages_exact(9)
• nr_free_zone_pages(9)
• nr_free_buffer_pages(9)
• find_next_best_node(9)
• free_reserved_pages(9)
• setup_per_zone_wmarks(9)
• __free_contig_range(9)
• alloc_contig_frozen_range(9)
• alloc_contig_range(9)
• alloc_contig_frozen_pages(9)
• alloc_contig_pages(9)
• free_contig_frozen_range(9)
• free_contig_range(9)
• alloc_pages_nolock(9)

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and that's the page, bestie 💜 huge shoutout to the source directory <pink>./mm</pink> and the date <cyan>October 2026</cyan> — this one dropped in October 2026 and honestly it ate 👑 see you in the next man page, mwah 🧚