global_dirty_limits(9)

💖 global_dirty_limits(9) 💖

okay so this is a page from the Kernel API Manual (yes bestie, the kernel has lore) and it's literally all about global_dirty_limits — the cutoff numbers that decide when the kernel starts stressing about dirty pages. iconic behavior honestly 🎀

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✨ NAME ✨

global_dirty_limits — the background-writeback and dirty-throttling thresholds 🦋

like, the two vibes the kernel uses to know when to chill and when to panic about dirty data. no cap.

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🌸 SYNOPSIS 🌸

void global_dirty_limits (unsigned long *pbackground , unsigned long *pdirty );

that's it. that's the whole signature. two pointers in, nothing out (it's a void, she doesn't return anything, she just fills your pointers and leaves 💅).

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🫶 ARGUMENTS 🫶

• pbackground — an out parameter for bg_thresh. you hand her a pointer, she writes the background threshold into it. you're not giving info, you're receiving it. main character energy on her part tbh ✨
• pdirty — an out parameter for thresh. same deal: she fills this one in with the dirty threshold. two outputs, zero drama 😌

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🔥 DESCRIPTION 🔥

so what does she actually do? she calculates bg_thresh and thresh for global_wb_domain. that's the whole job. those are the two numbers you asked for and she delivers them through your out parameters 🧚

and if you want the full tea on how it all works? the page says to see domain_dirty_limits for details. so like, go read that one, she's the one with the actual explanation 💜

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🦋 SEE ALSO 🦋

this is the little friend group she runs with, iykyk 🍓

Kernel file ./mm/page-writeback.c, plus:

• node_dirtyable_memory(9)
• global_dirtyable_memory(9)
• domain_dirty_limits(9)
• node_dirty_limit(9)
• node_dirty_ok(9)
• __wb_calc_thresh(9)
• balance_dirty_pages_ratelimited_flags(9)
• balance_dirty_pages_ratelimited(9)
• wb_over_bg_thresh(9)
• tag_pages_for_writeback(9)
• writeback_iter(9)
• filemap_dirty_folio(9)
• folio_redirty_for_writepage(9)
• folio_mark_dirty(9)
• folio_wait_writeback(9)
• folio_wait_writeback_killable(9)
• folio_wait_stable(9)

go read them, they're all slaying in their own ways 👑

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reminder bestie: she writes through pbackground and pdirty, so those pointers better be real and valid. do not pass her a vibe. pass her an actual unsigned long * 🙈

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and that's the page!! 🎀 this one lives in ./mm, dated October 2026, and it's filed under the name global_dirty_limits(9). periodt. 💜✨