lruvec_page_state_monotonic(9)

💅 lruvec_page_state_monotonic(9) — Kernel API Manual 💅

Okay bestie, this is the manual page for lruvec_page_state_monotonic(9) — manual name folded in right at the top, we're so back. It's the non-clamping lruvec stat read for delta sampling. Slay. ✨

🌸 NAME 🌸

lruvec_page_state_monotonic — non-clamping lruvec stat read for delta sampling.

✨ SYNOPSIS ✨

unsigned long lruvec_page_state_monotonic (struct lruvec *lruvec , enum
node_stat_item idx );

🎀 ARGUMENTS 🎀

• lruvec — the LRU vector to read from. That's the source, bestie.
• idx — the node_stat_item to read. The exact stat you're pulling up.

🦋 DESCRIPTION 🦋

So this function returns the raw state[idx] value cast to unsigned long, and the whole glow-up is that it skips the clamp-negative-to-zero step that lives in lruvec_page_state. No cap.

It's intended for callers that snapshot a monotonically-incremented counter and then subtract two samples. With unsigned modular arithmetic, that subtraction yields the correct delta across a signed-long wraparound — which is a real hazard on 32-bit — and that wraparound would otherwise be turned into a huge spurious delta by the clamp. Literally iconic behavior. 👑

Do NOT use this for non-monotonic page-count reads where a transient negative reading from per-CPU delta skew must present as zero. That is not the moment, bestie. 🙈

XXX: This helper (and its node/global peers) exists because some monotonically-incremented event counters are stored in enum node_stat_item. That's the tea. 🍵

👑 SEE ALSO 👑

Kernel file ./mm/memcontrol.c plus this whole referenced crew:

• get_mem_cgroup_css_from_folio(9)
• page_cgroup_ino(9)
• mod_memcg_state(9)
• mod_lruvec_state(9)
• count_memcg_events(9)
• get_mem_cgroup_from_mm(9)
• get_mem_cgroup_from_current(9)
• get_mem_cgroup_from_folio(9)
• mem_cgroup_iter(9)
• mem_cgroup_iter_break(9)
• mem_cgroup_scan_tasks(9)
• folio_lruvec_lock(9)
• folio_lruvec_lock_irq(9)
• folio_lruvec_lock_irqsave(9)
• mem_cgroup_update_lru_size(9)
• mem_cgroup_margin(9)
• mem_cgroup_print_oom_context(9)
• mem_cgroup_print_oom_meminfo(9)
• mem_cgroup_get_oom_group(9)
• consume_stock(9)
• __memcg_kmem_charge_page(9)
• __memcg_kmem_uncharge_page(9)
• mem_cgroup_wb_stats(9)
• mem_cgroup_from_private_id(9)
• mem_cgroup_css_reset(9)
• mem_cgroup_calculate_protection(9)
• mem_cgroup_charge_hugetlb(9)
• mem_cgroup_swapin_charge_folio(9)
• mem_cgroup_replace_folio(9)
• mem_cgroup_migrate(9)
• mem_cgroup_sk_charge(9)
• mem_cgroup_sk_uncharge(9)
• __mem_cgroup_try_charge_swap(9)
• __mem_cgroup_uncharge_swap(9)
• obj_cgroup_may_zswap(9)
• obj_cgroup_charge_zswap(9)
• obj_cgroup_uncharge_zswap(9)

Source/version: ./mm · Date: October 2026 · lruvec_page_state_monotonic(9) — bye bestie, go snapshot those counters and stay monotonic 💖✨