domain_dirty_limits(9)

💖 domain_dirty_limits(9) 💖

okay so welcome to domain_dirty_limits, bestie — it's a kernel API manual entry (section 9, the fancy "kernel developer" section 🎀) and honestly it's giving "tiny function, huge responsibilities."

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✨ NAME ✨

domain_dirty_limits — literally just: calculate thresh and bg_thresh for a wb_domain. that's the whole vibe. no cap.

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🦋 SYNOPSIS 🦋

void domain_dirty_limits (struct dirty_throttle_control *dtc );

yes queen, that's the entire signature. void in, vibes out. 💅

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🌸 ARGUMENTS 🌸

• dtc — the dirty_throttle_control of interest 💖. like, the specific one you care about. your main character struct, if you will.

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👑 DESCRIPTION 👑

so here's what's actually happening, and it's lowkey important:

domain_dirty_limits calculates dtc->thresh and ->bg_thresh, and it does that by considering vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}. those four knobs are the whole personality of this function ngl. 🫶

⚠️ the caller MUST ensure that dtc->avail is set before calling this function. like, must must. not "should", not "eh probably". you set dtc->avail first, then you call. please and thank you 🙏

and the cute little plot twist: the dirty limits will be lifted by 1/4 for real-time tasks. so RT tasks get that extra quarter headroom — iconic behaviour, honestly. ✨🔥

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💀 SEE ALSO 💀

okay this list is long long, but we don't skip. we never skip. everything's here, bestie:

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

• node_dirtyable_memory(9)
• global_dirtyable_memory(9)
• global_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)

iykyk, this is the whole writeback friend group 🌈💜

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made with love in the ./mm directory, dated October 2026, and this little entry is officially titled domain_dirty_limits(9) — mwah, go set your dtc->avail and slay 🎀💖✨