diff options
| -rw-r--r-- | Documentation/admin-guide/pm/intel_pstate.rst | 61 | ||||
| -rw-r--r-- | drivers/cpufreq/intel_pstate.c | 276 |
2 files changed, 10 insertions, 327 deletions
diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index 1d6249825efc..d2b6fda3d67b 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -167,35 +167,17 @@ is set. ``powersave`` ............. -Without HWP, this P-state selection algorithm generally depends on the -processor model and/or the system profile setting in the ACPI tables and there -are two variants of it. - -One of them is used with processors from the Atom line and (regardless of the -processor model) on platforms with the system profile in the ACPI tables set to -"mobile" (laptops mostly), "tablet", "appliance PC", "desktop", or -"workstation". It is also used with processors supporting the HWP feature if -that feature has not been enabled (that is, with the ``intel_pstate=no_hwp`` -argument in the kernel command line). It is similar to the algorithm +Without HWP, this P-state selection algorithm is similar to the algorithm implemented by the generic ``schedutil`` scaling governor except that the utilization metric used by it is based on numbers coming from feedback registers of the CPU. It generally selects P-states proportional to the -current CPU utilization, so it is referred to as the "proportional" algorithm. - -The second variant of the ``powersave`` P-state selection algorithm, used in all -of the other cases (generally, on processors from the Core line, so it is -referred to as the "Core" algorithm), is based on the values read from the APERF -and MPERF feedback registers and the previously requested target P-state. -It does not really take CPU utilization into account explicitly, but as a rule -it causes the CPU P-state to ramp up very quickly in response to increased -utilization which is generally desirable in server environments. - -Regardless of the variant, this algorithm is run by the driver's utilization -update callback for the given CPU when it is invoked by the CPU scheduler, but -not more often than every 10 ms (that can be tweaked via ``debugfs`` in `this -particular case <Tuning Interface in debugfs_>`_). Like in the ``performance`` -case, the hardware configuration is not touched if the new P-state turns out to -be the same as the current one. +current CPU utilization. + +This algorithm is run by the driver's utilization update callback for the +given CPU when it is invoked by the CPU scheduler, but not more often than +every 10 ms. Like in the ``performance`` case, the hardware configuration +is not touched if the new P-state turns out to be the same as the current +one. This is the default P-state selection algorithm if the :c:macro:`CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE` kernel configuration option @@ -720,34 +702,7 @@ P-state is called, the ``ftrace`` filter can be set to to gnome-shell-3409 [001] ..s. 2537.650850: intel_pstate_set_pstate <-intel_pstate_timer_func <idle>-0 [000] ..s. 2537.654843: intel_pstate_set_pstate <-intel_pstate_timer_func -Tuning Interface in ``debugfs`` -------------------------------- - -The ``powersave`` algorithm provided by ``intel_pstate`` for `the Core line of -processors in the active mode <powersave_>`_ is based on a `PID controller`_ -whose parameters were chosen to address a number of different use cases at the -same time. However, it still is possible to fine-tune it to a specific workload -and the ``debugfs`` interface under ``/sys/kernel/debug/pstate_snb/`` is -provided for this purpose. [Note that the ``pstate_snb`` directory will be -present only if the specific P-state selection algorithm matching the interface -in it actually is in use.] - -The following files present in that directory can be used to modify the PID -controller parameters at run time: - -| ``deadband`` -| ``d_gain_pct`` -| ``i_gain_pct`` -| ``p_gain_pct`` -| ``sample_rate_ms`` -| ``setpoint`` - -Note, however, that achieving desirable results this way generally requires -expert-level understanding of the power vs performance tradeoff, so extra care -is recommended when attempting to do that. - .. _LCEU2015: http://events.linuxfoundation.org/sites/events/files/slides/LinuxConEurope_2015.pdf .. _SDM: http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-system-programming-manual-325384.html .. _ACPI specification: http://www.uefi.org/sites/default/files/resources/ACPI_6_1.pdf -.. _PID controller: https://en.wikipedia.org/wiki/PID_controller diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 6cd503525638..0eedc4f04a44 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -173,28 +173,6 @@ struct vid_data { }; /** - * struct _pid - Stores PID data - * @setpoint: Target set point for busyness or performance - * @integral: Storage for accumulated error values - * @p_gain: PID proportional gain - * @i_gain: PID integral gain - * @d_gain: PID derivative gain - * @deadband: PID deadband - * @last_err: Last error storage for integral part of PID calculation - * - * Stores PID coefficients and last error for PID controller. - */ -struct _pid { - int setpoint; - int32_t integral; - int32_t p_gain; - int32_t i_gain; - int32_t d_gain; - int deadband; - int32_t last_err; -}; - -/** * struct global_params - Global parameters, mostly tunable via sysfs. * @no_turbo: Whether or not to use turbo P-states. * @turbo_disabled: Whethet or not turbo P-states are available at all, @@ -223,7 +201,6 @@ struct global_params { * @last_update: Time of the last update. * @pstate: Stores P state limits for this CPU * @vid: Stores VID limits for this CPU - * @pid: Stores PID parameters for this CPU * @last_sample_time: Last Sample time * @aperf_mperf_shift: Number of clock cycles after aperf, merf is incremented * This shift is a multiplier to mperf delta to @@ -258,7 +235,6 @@ struct cpudata { struct pstate_data pstate; struct vid_data vid; - struct _pid pid; u64 last_update; u64 last_sample_time; @@ -284,28 +260,6 @@ struct cpudata { static struct cpudata **all_cpu_data; /** - * struct pstate_adjust_policy - Stores static PID configuration data - * @sample_rate_ms: PID calculation sample rate in ms - * @sample_rate_ns: Sample rate calculation in ns - * @deadband: PID deadband - * @setpoint: PID Setpoint - * @p_gain_pct: PID proportional gain - * @i_gain_pct: PID integral gain - * @d_gain_pct: PID derivative gain - * - * Stores per CPU model static PID configuration data. - */ -struct pstate_adjust_policy { - int sample_rate_ms; - s64 sample_rate_ns; - int deadband; - int setpoint; - int p_gain_pct; - int d_gain_pct; - int i_gain_pct; -}; - -/** * struct pstate_funcs - Per CPU model specific callbacks * @get_max: Callback to get maximum non turbo effective P state * @get_max_physical: Callback to get maximum non turbo physical P state @@ -333,15 +287,6 @@ struct pstate_funcs { }; static struct pstate_funcs pstate_funcs __read_mostly; -static struct pstate_adjust_policy pid_params __read_mostly = { - .sample_rate_ms = 10, - .sample_rate_ns = 10 * NSEC_PER_MSEC, - .deadband = 0, - .setpoint = 97, - .p_gain_pct = 20, - .d_gain_pct = 0, - .i_gain_pct = 0, -}; static int hwp_active __read_mostly; static bool per_cpu_limits __read_mostly; @@ -509,56 +454,6 @@ static inline void intel_pstate_exit_perf_limits(struct cpufreq_policy *policy) } #endif -static signed int pid_calc(struct _pid *pid, int32_t busy) -{ - signed int result; - int32_t pterm, dterm, fp_error; - int32_t integral_limit; - - fp_error = pid->setpoint - busy; - - if (abs(fp_error) <= pid->deadband) - return 0; - - pterm = mul_fp(pid->p_gain, fp_error); - - pid->integral += fp_error; - - /* - * We limit the integral here so that it will never - * get higher than 30. This prevents it from becoming - * too large an input over long periods of time and allows - * it to get factored out sooner. - * - * The value of 30 was chosen through experimentation. - */ - integral_limit = int_tofp(30); - if (pid->integral > integral_limit) - pid->integral = integral_limit; - if (pid->integral < -integral_limit) - pid->integral = -integral_limit; - - dterm = mul_fp(pid->d_gain, fp_error - pid->last_err); - pid->last_err = fp_error; - - result = pterm + mul_fp(pid->integral, pid->i_gain) + dterm; - result = result + (1 << (FRAC_BITS-1)); - return (signed int)fp_toint(result); -} - -static inline void intel_pstate_pid_reset(struct cpudata *cpu) -{ - struct _pid *pid = &cpu->pid; - - pid->p_gain = percent_fp(pid_params.p_gain_pct); - pid->d_gain = percent_fp(pid_params.d_gain_pct); - pid->i_gain = percent_fp(pid_params.i_gain_pct); - pid->setpoint = int_tofp(pid_params.setpoint); - pid->last_err = pid->setpoint - int_tofp(100); - pid->deadband = int_tofp(pid_params.deadband); - pid->integral = 0; -} - static inline void update_turbo_state(void) { u64 misc_en; @@ -911,82 +806,6 @@ static void intel_pstate_update_policies(void) cpufreq_update_policy(cpu); } -/************************** debugfs begin ************************/ -static int pid_param_set(void *data, u64 val) -{ - unsigned int cpu; - - *(u32 *)data = val; - pid_params.sample_rate_ns = pid_params.sample_rate_ms * NSEC_PER_MSEC; - for_each_possible_cpu(cpu) - if (all_cpu_data[cpu]) - intel_pstate_pid_reset(all_cpu_data[cpu]); - - return 0; -} - -static int pid_param_get(void *data, u64 *val) -{ - *val = *(u32 *)data; - return 0; -} -DEFINE_SIMPLE_ATTRIBUTE(fops_pid_param, pid_param_get, pid_param_set, "%llu\n"); - -static struct dentry *debugfs_parent; - -struct pid_param { - char *name; - void *value; - struct dentry *dentry; -}; - -static struct pid_param pid_files[] = { - {"sample_rate_ms", &pid_params.sample_rate_ms, }, - {"d_gain_pct", &pid_params.d_gain_pct, }, - {"i_gain_pct", &pid_params.i_gain_pct, }, - {"deadband", &pid_params.deadband, }, - {"setpoint", &pid_params.setpoint, }, - {"p_gain_pct", &pid_params.p_gain_pct, }, - {NULL, NULL, } -}; - -static void intel_pstate_debug_expose_params(void) -{ - int i; - - debugfs_parent = debugfs_create_dir("pstate_snb", NULL); - if (IS_ERR_OR_NULL(debugfs_parent)) - return; - - for (i = 0; pid_files[i].name; i++) { - struct dentry *dentry; - - dentry = debugfs_create_file(pid_files[i].name, 0660, - debugfs_parent, pid_files[i].value, - &fops_pid_param); - if (!IS_ERR(dentry)) - pid_files[i].dentry = dentry; - } -} - -static void intel_pstate_debug_hide_params(void) -{ - int i; - - if (IS_ERR_OR_NULL(debugfs_parent)) - return; - - for (i = 0; pid_files[i].name; i++) { - debugfs_remove(pid_files[i].dentry); - pid_files[i].dentry = NULL; - } - - debugfs_remove(debugfs_parent); - debugfs_parent = NULL; -} - -/************************** debugfs end ************************/ - /************************** sysfs begin ************************/ #define show_one(file_name, object) \ static ssize_t show_##file_name \ @@ -1661,44 +1480,6 @@ static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu) return target; } -static inline int32_t get_target_pstate_use_performance(struct cpudata *cpu) -{ - int32_t perf_scaled, max_pstate, current_pstate, sample_ratio; - u64 duration_ns; - - /* - * perf_scaled is the ratio of the average P-state during the last - * sampling period to the P-state requested last time (in percent). - * - * That measures the system's response to the previous P-state - * selection. - */ - max_pstate = cpu->pstate.max_pstate_physical; - current_pstate = cpu->pstate.current_pstate; - perf_scaled = mul_ext_fp(cpu->sample.core_avg_perf, - div_fp(100 * max_pstate, current_pstate)); - - /* - * Since our utilization update callback will not run unless we are - * in C0, check if the actual elapsed time is significantly greater (3x) - * than our sample interval. If it is, then we were idle for a long - * enough period of time to adjust our performance metric. - */ - duration_ns = cpu->sample.time - cpu->last_sample_time; - if ((s64)duration_ns > pid_params.sample_rate_ns * 3) { - sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns); - perf_scaled = mul_fp(perf_scaled, sample_ratio); - } else { - sample_ratio = div_fp(100 * (cpu->sample.mperf << cpu->aperf_mperf_shift), - cpu->sample.tsc); - if (sample_ratio < int_tofp(1)) - perf_scaled = 0; - } - - cpu->sample.busy_scaled = perf_scaled; - return cpu->pstate.current_pstate - pid_calc(&cpu->pid, perf_scaled); -} - static int intel_pstate_prepare_request(struct cpudata *cpu, int pstate) { int max_pstate = intel_pstate_get_base_pstate(cpu); @@ -1741,23 +1522,6 @@ static void intel_pstate_adjust_pstate(struct cpudata *cpu, int target_pstate) fp_toint(cpu->iowait_boost * 100)); } -static void intel_pstate_update_util_pid(struct update_util_data *data, - u64 time, unsigned int flags) -{ - struct cpudata *cpu = container_of(data, struct cpudata, update_util); - u64 delta_ns = time - cpu->sample.time; - - if ((s64)delta_ns < pid_params.sample_rate_ns) - return; - - if (intel_pstate_sample(cpu, time)) { - int target_pstate; - - target_pstate = get_target_pstate_use_performance(cpu); - intel_pstate_adjust_pstate(cpu, target_pstate); - } -} - static void intel_pstate_update_util(struct update_util_data *data, u64 time, unsigned int flags) { @@ -1792,7 +1556,7 @@ static struct pstate_funcs core_funcs = { .get_turbo = core_get_turbo_pstate, .get_scaling = core_get_scaling, .get_val = core_get_val, - .update_util = intel_pstate_update_util_pid, + .update_util = intel_pstate_update_util, }; static const struct pstate_funcs silvermont_funcs = { @@ -1825,7 +1589,7 @@ static const struct pstate_funcs knl_funcs = { .get_aperf_mperf_shift = knl_get_aperf_mperf_shift, .get_scaling = core_get_scaling, .get_val = core_get_val, - .update_util = intel_pstate_update_util_pid, + .update_util = intel_pstate_update_util, }; static const struct pstate_funcs bxt_funcs = { @@ -1879,8 +1643,6 @@ static const struct x86_cpu_id intel_pstate_cpu_ee_disable_ids[] = { {} }; -static bool pid_in_use(void); - static int intel_pstate_init_cpu(unsigned int cpunum) { struct cpudata *cpu; @@ -1911,8 +1673,6 @@ static int intel_pstate_init_cpu(unsigned int cpunum) intel_pstate_disable_ee(cpunum); intel_pstate_hwp_enable(cpu); - } else if (pid_in_use()) { - intel_pstate_pid_reset(cpu); } intel_pstate_get_cpu_pstates(cpu); @@ -2270,12 +2030,6 @@ static struct cpufreq_driver intel_cpufreq = { static struct cpufreq_driver *default_driver = &intel_pstate; -static bool pid_in_use(void) -{ - return intel_pstate_driver == &intel_pstate && - pstate_funcs.update_util == intel_pstate_update_util_pid; -} - static void intel_pstate_driver_cleanup(void) { unsigned int cpu; @@ -2310,9 +2064,6 @@ static int intel_pstate_register_driver(struct cpufreq_driver *driver) global.min_perf_pct = min_perf_pct_min(); - if (pid_in_use()) - intel_pstate_debug_expose_params(); - return 0; } @@ -2321,9 +2072,6 @@ static int intel_pstate_unregister_driver(void) if (hwp_active) return -EBUSY; - if (pid_in_use()) - intel_pstate_debug_hide_params(); - cpufreq_unregister_driver(intel_pstate_driver); intel_pstate_driver_cleanup(); @@ -2391,24 +2139,6 @@ static int __init intel_pstate_msrs_not_valid(void) return 0; } -#ifdef CONFIG_ACPI -static void intel_pstate_use_acpi_profile(void) -{ - switch (acpi_gbl_FADT.preferred_profile) { - case PM_MOBILE: - case PM_TABLET: - case PM_APPLIANCE_PC: - case PM_DESKTOP: - case PM_WORKSTATION: - pstate_funcs.update_util = intel_pstate_update_util; - } -} -#else -static void intel_pstate_use_acpi_profile(void) -{ -} -#endif - static void __init copy_cpu_funcs(struct pstate_funcs *funcs) { pstate_funcs.get_max = funcs->get_max; @@ -2420,8 +2150,6 @@ static void __init copy_cpu_funcs(struct pstate_funcs *funcs) pstate_funcs.get_vid = funcs->get_vid; pstate_funcs.update_util = funcs->update_util; pstate_funcs.get_aperf_mperf_shift = funcs->get_aperf_mperf_shift; - - intel_pstate_use_acpi_profile(); } #ifdef CONFIG_ACPI |