em_dev_compute_costs(9)

em_dev_compute_costs(9) 💅✨

okay so bestie, this one comes from the Kernel API Manual, and it’s giving “kernel energy model cost-crunching era” 🔥. We’re talking about em_dev_compute_costs, and yes, it’s exactly as iconic as it sounds.

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✨ NAME ✨

em_dev_compute_costs — calculate the cost values for a new runtime EM table, no cap 💖

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🌸 SYNOPSIS 🌸

int em_dev_compute_costs (struct device *dev , struct em_perf_state
       *table , int nr_states );

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🎀 ARGUMENTS 🎀

• dev — the device for which the EM table is to be updated 🫶
• table — the new EM table that is going to get the costs calculated ✨
• nr_states — number of performance states, i.e. how many states we’re working with 💅

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💖 DESCRIPTION 💖

okay so what this function does is calculate the em_perf_state::cost values for a new runtime EM table. Those values are used for EAS during task placement — literally main character energy for scheduling 🌈.

It also calculates and sets the efficiency flag for each performance state. So every performance state gets its little efficiency moment, periodt 💅.

When the function finishes successfully, the EM table is ready to be updated and used by EAS. That’s the vibe check passing ✅.

Return 0 on success, or a proper error in case of failure. No guessing, bestie — 0 means slay, and an error means something went sideways 😭.

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🔥 SEE ALSO 🔥

• Kernel file ./kernel/power/energy_model.c
• em_table_free(9)
• em_table_alloc(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_adjust_cpu_capacity(9)
• em_dev_update_chip_binning(9)
• em_update_performance_limits(9)

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mwah 💋 this page lives under ./kernel/power, dated October 2026, and it’s em_dev_compute_costs(9) signing off 🫶✨