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c1d51f684c
Currently, the cpuidle subsystem uses microseconds as the unit of time which (among other things) causes the idle loop to incur some integer division overhead for no clear benefit. In order to allow cpuidle to measure time in nanoseconds, add two new fields, exit_latency_ns and target_residency_ns, to represent the exit latency and target residency of an idle state in nanoseconds, respectively, to struct cpuidle_state and initialize them with the help of the corresponding values in microseconds provided by drivers. Additionally, change cpuidle_governor_latency_req() to return the idle state exit latency constraint in nanoseconds. Also meeasure idle state residency (last_residency_ns in struct cpuidle_device and time_ns in struct cpuidle_driver) in nanoseconds and update the cpuidle core and governors accordingly. However, the menu governor still computes typical intervals in microseconds to avoid integer overflows. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Doug Smythies <dsmythies@telus.net> Tested-by: Doug Smythies <dsmythies@telus.net>
120 lines
2.8 KiB
C
120 lines
2.8 KiB
C
/*
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* governor.c - governor support
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*
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* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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* Shaohua Li <shaohua.li@intel.com>
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* Adam Belay <abelay@novell.com>
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*
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* This code is licenced under the GPL.
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*/
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#include <linux/cpu.h>
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#include <linux/cpuidle.h>
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#include <linux/mutex.h>
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#include <linux/module.h>
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#include <linux/pm_qos.h>
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#include "cpuidle.h"
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char param_governor[CPUIDLE_NAME_LEN];
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LIST_HEAD(cpuidle_governors);
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struct cpuidle_governor *cpuidle_curr_governor;
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struct cpuidle_governor *cpuidle_prev_governor;
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/**
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* cpuidle_find_governor - finds a governor of the specified name
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* @str: the name
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*
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* Must be called with cpuidle_lock acquired.
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*/
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struct cpuidle_governor *cpuidle_find_governor(const char *str)
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{
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struct cpuidle_governor *gov;
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list_for_each_entry(gov, &cpuidle_governors, governor_list)
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if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
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return gov;
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return NULL;
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}
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/**
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* cpuidle_switch_governor - changes the governor
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* @gov: the new target governor
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* Must be called with cpuidle_lock acquired.
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*/
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int cpuidle_switch_governor(struct cpuidle_governor *gov)
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{
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struct cpuidle_device *dev;
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if (!gov)
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return -EINVAL;
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if (gov == cpuidle_curr_governor)
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return 0;
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cpuidle_uninstall_idle_handler();
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if (cpuidle_curr_governor) {
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list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
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cpuidle_disable_device(dev);
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}
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cpuidle_curr_governor = gov;
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if (gov) {
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list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
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cpuidle_enable_device(dev);
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cpuidle_install_idle_handler();
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printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
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}
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return 0;
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}
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/**
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* cpuidle_register_governor - registers a governor
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* @gov: the governor
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*/
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int cpuidle_register_governor(struct cpuidle_governor *gov)
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{
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int ret = -EEXIST;
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if (!gov || !gov->select)
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return -EINVAL;
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if (cpuidle_disabled())
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return -ENODEV;
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mutex_lock(&cpuidle_lock);
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if (cpuidle_find_governor(gov->name) == NULL) {
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ret = 0;
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list_add_tail(&gov->governor_list, &cpuidle_governors);
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if (!cpuidle_curr_governor ||
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!strncasecmp(param_governor, gov->name, CPUIDLE_NAME_LEN) ||
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(cpuidle_curr_governor->rating < gov->rating &&
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strncasecmp(param_governor, cpuidle_curr_governor->name,
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CPUIDLE_NAME_LEN)))
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cpuidle_switch_governor(gov);
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}
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mutex_unlock(&cpuidle_lock);
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return ret;
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}
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/**
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* cpuidle_governor_latency_req - Compute a latency constraint for CPU
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* @cpu: Target CPU
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*/
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s64 cpuidle_governor_latency_req(unsigned int cpu)
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{
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int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
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struct device *device = get_cpu_device(cpu);
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int device_req = dev_pm_qos_raw_resume_latency(device);
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if (device_req > global_req)
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device_req = global_req;
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return (s64)device_req * NSEC_PER_USEC;
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}
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