em_adjust_cpu_capacity(9)

💅 em_adjust_cpu_capacity(9) — the Kernel API Manual, bestie edition

okay so you're reading em_adjust_cpu_capacity(9), which lives in section 9 of the Kernel API Manual (that's the kernel-functions section, iykyk ✨). It's about the EM — energy model — and yes we're gonna get into it. 🦋

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🌸 NAME 🌸

em_adjust_cpu_capacity — literally just going in and adjusting the EM for a CPU after its capacity got updated. that's the whole vibe. 💖

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✨ SYNOPSIS ✨

void em_adjust_cpu_capacity (unsigned int cpu );

that's it. that's the call. she's short but she's doing her job. 🎀

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🫶 ARGUMENTS 🫶

• cpu — the target CPU. like, which CPU are we doing this to. that one. 👑

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🔥 DESCRIPTION 🔥

So here's the situation: you adjust the existing EM for cpu after a capacity update. ✅

But bestie, there's an assumption baked in here, and you need to know it: this works under the assumption that the capacity has been updated in the same way for all of the CPUs in the same perf domain. same perf domain = same treatment, no cap. it's giving "we're all in this together" energy. 💀✨

So yeah — one CPU gets named in cpu, but the mental model is the whole perf domain moving together. got it? perfect. 💜

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🌈 SEE ALSO 🌈

The kernel file lives at ./kernel/power/energy_model.c, and here's the whole friend group you should go meet:

• em_table_free(9)
• em_table_alloc(9)
• em_dev_compute_costs(9)
• em_dev_update_perf_domain(9)
• em_pd_get(9)
• em_cpu_get(9)
• em_dev_register_perf_domain(9)
• em_dev_register_pd_no_update(9)
• em_dev_unregister_perf_domain(9)
• em_dev_update_chip_binning(9)
• em_update_performance_limits(9)

go read them. they're all icons in their own right. 👑⭐🧚

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lowkey reminder: everything above is the actual documented behaviour — nothing more, nothing less. no guessing, no extra lore. 🙈

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and that's the page!! sign-off time: this gem comes from the ./kernel/power source tree, dated October 2026, and yeah — she ate. 💅🍓🎀 periodt.