STRUCT CPUDATA(9)

💖 struct cpudata(9) — the Kernel API Manual glow-up ✨

okay so bestie, meet struct cpudata, from the Kernel API Manual. it's literally the per-CPU instance data storage — every CPU gets its own little locker of state, and this struct is the locker. iconic behavior honestly 🎀

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🌸 NAME 🌸

struct cpudata — per CPU instance data storage. yes that's the whole name. she's simple, she's efficient, she's slaying 💅

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✨ SYNOPSIS ✨

here's the whole shape of her, verbatim, don't touch a single character or the compiler WILL come for you:

struct cpudata {
    int cpu;
    unsigned int policy;
    struct update_util_data update_util;
    bool update_util_set;
    struct pstate_data pstate;
    struct vid_data vid;
    u64 last_update;
    u64 last_sample_time;
    u64 aperf_mperf_shift;
    u64 prev_aperf;
    u64 prev_mperf;
    u64 prev_tsc;
    struct sample sample;
    int32_t min_perf_ratio;
    int32_t max_perf_ratio;
  #ifdef CONFIG_ACPI;
    struct acpi_processor_performance acpi_perf_data;
    bool valid_pss_table;
  #endif;
    unsigned int iowait_boost;
    s16 epp_powersave;
    s16 epp_policy;
    s16 epp_default;
    s16 epp_cached;
    u64 hwp_req_cached;
    u64 hwp_cap_cached;
    u64 last_io_update;
    unsigned int capacity_perf;
    unsigned int sched_flags;
    u32 hwp_boost_min;
    bool suspended;
  #ifdef CONFIG_ENERGY_MODEL;
    bool pd_registered;
  #endif;
    struct delayed_work hwp_notify_work;
   };

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🦋 Members 🦋

every field, one by one, no skipping, no cap:

• cpu — CPU number for this instance data. which CPU's locker this is 🫶
• policy — CPUFreq policy value
• update_util — CPUFreq utility callback information
• update_util_set — CPUFreq utility callback is set
• pstate — Stores P state limits for this CPU
• vid — Stores VID limits for this CPU
• last_update — Time of the last update.
• last_sample_time — Last Sample time
• aperf_mperf_shift — APERF vs MPERF counting frequency difference
• prev_aperf — Last APERF value read from APERF MSR
• prev_mperf — Last MPERF value read from MPERF MSR
• prev_tsc — Last timestamp counter (TSC) value
• sample — Storage for storing last Sample data
• min_perf_ratio — Minimum capacity in terms of PERF or HWP ratios
• max_perf_ratio — Maximum capacity in terms of PERF or HWP ratios
• acpi_perf_data — Stores ACPI perf information read from _PSS
• valid_pss_table — Set to true for valid ACPI _PSS entries found
• iowait_boost — iowait-related boost fraction
• epp_powersave — Last saved HWP energy performance preference (EPP) or energy performance bias (EPB), when policy switched to performance
• epp_policy — Last saved policy used to set EPP/EPB
• epp_default — Power on default HWP energy performance preference/bias
• epp_cached — Cached HWP energy-performance preference value
• hwp_req_cached — Cached value of the last HWP Request MSR
• hwp_cap_cached — Cached value of the last HWP Capabilities MSR
• last_io_update — Last time when IO wake flag was set
• capacity_perf — Highest perf used for scale invariance
• sched_flags — Store scheduler flags for possible cross CPU update
• hwp_boost_min — Last HWP boosted min performance
• suspended — Whether or not the driver has been suspended.
• pd_registered — Set when a perf domain is registered for this CPU.
• hwp_notify_work — workqueue for HWP notifications.

💀 tiny heads-up for the girlies reading the synopsis: those #ifdef CONFIG_ACPI; and #ifdef CONFIG_ENERGY_MODEL; lines gate fields, so acpi_perf_data, valid_pss_table and pd_registered only exist when those configs are in play. they're listed above anyway because we're being thorough. periodt.

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👑 Description 👑

This structure stores per CPU instance data for all CPUs. that's it, that's the vibe — one of these per CPU, all of them holding that CPU's personal little stash of state. literally main character energy, multiplied by your core count 💜

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🌈 SEE ALSO 🌈

go read these next, iykyk:

Kernel file ./drivers/cpufreq/intel_pstate.c struct sample(9), struct pstate_data(9), struct vid_data(9), struct global_params(9), struct pstate_funcs(9)

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and that's the page bestie!! 🍓 this whole thing lives under ./drivers/cpufreq, dated October 2026, and it's filed as struct cpudata(9) — so if you ever need to find her again, that's the tag 💖 mwah, go read struct sample(9) next, love u 🧚