vmpressure_register_event(9)

💅 vmpressure_register_event (kernel API manual, bestie!) 💅

okay so real talk, this one's from the Kernel API Manual and it's genuinely such a vibe once you get what it's doing. sit down, grab a strawberry, we're linking memory pressure to an eventfd and it's gonna slay 🍓✨

🌸 NAME 🌸

vmpressure_register_event — bind vmpressure notifications to an eventfd 💖

like, that's literally it. that's the whole thing. notifications → eventfd. iconic behavior.

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⭐ SYNOPSIS ⭐

int vmpressure_register_event (struct mem_cgroup *memcg , struct
eventfd_ctx *eventfd , const char *args );

no cap, that's the exact signature, character for character, don't come for me 🫶

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🦋 ARGUMENTS 🦋

• memcg — the mem_cgroup that's interested in vmpressure notifications. this is the main character of the operation tbh 👑
• eventfd — the eventfd_ctx we're linking notifications with. the messenger bestie 💌
• args — the event arguments: a pressure level threshold, plus an optional mode. yes it's a string, yes it's parsed, we'll get to it 🌈

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🎀 DESCRIPTION 🎀

so what this function does is associate that eventfd context with the vmpressure infrastructure, so the notifications get delivered to the eventfd. literally the whole point. slay 💅

the args parameter is a comma-delimited string that denotes a pressure level threshold — one of vmpressure_str_levels, i.e. "low", "medium", or "critical" — and an optional mode, which is one of vmpressure_str_modes, i.e. "hierarchy" or "local".

that's the tea: threshold first, mode optional. iykyk 🧚

also important: to be used as an memcg event method. periodt.

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🔥 RETURN 🔥

• 0 on success 🎉
• -ENOMEM on memory failure 😭
• -EINVAL if args could not be parsed 💀

ngl the -EINVAL one is giving "check your comma string, bestie" energy. vibe check your args before you call this fr fr 🙈

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👑 SEE ALSO 👑

kernel file ./mm/memcontrol-v1.c, plus these icons:

• __memcg1_swapout(9)
• memcg1_swapin(9)
• mem_cgroup_oom_synchronize(9)
• vmpressure_prio(9)
• vmpressure_unregister_event(9)

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and that's the whole page, bestie 🫶 this one lives over in ./mm and it's dated October 2026 — shoutout to the source/version and date, we love a documented footer ✨🌸 go forth and register those events 💖