linux_dsm_epyc7002/drivers/cpufreq/cpufreq_governor.c
Viresh Kumar 70f43e5e79 cpufreq: governor: replace per-CPU delayed work with timers
cpufreq governors evaluate load at sampling rate and based on that they
update frequency for a group of CPUs belonging to the same cpufreq
policy.

This is required to be done in a single thread for all policy->cpus, but
because we don't want to wakeup idle CPUs to do just that, we use
deferrable work for this. If we would have used a single delayed
deferrable work for the entire policy, there were chances that the CPU
required to run the handler can be in idle and we might end up not
changing the frequency for the entire group with load variations.

And so we were forced to keep per-cpu works, and only the one that
expires first need to do the real work and others are rescheduled for
next sampling time.

We have been using the more complex solution until now, where we used a
delayed deferrable work for this, which is a combination of a timer and
a work.

This could be made lightweight by keeping per-cpu deferred timers with a
single work item, which is scheduled by the first timer that expires.

This patch does just that and here are important changes:
- The timer handler will run in irq context and so we need to use a
  spin_lock instead of the timer_mutex. And so a separate timer_lock is
  created. This also makes the use of the mutex and lock quite clear, as
  we know what exactly they are protecting.
- A new field 'skip_work' is added to track when the timer handlers can
  queue a work. More comments present in code.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-12-09 22:26:00 +01:00

594 lines
16 KiB
C

/*
* drivers/cpufreq/cpufreq_governor.c
*
* CPUFREQ governors common code
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
* (C) 2009 Alexander Clouter <alex@digriz.org.uk>
* (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/export.h>
#include <linux/kernel_stat.h>
#include <linux/slab.h>
#include "cpufreq_governor.h"
static struct attribute_group *get_sysfs_attr(struct dbs_data *dbs_data)
{
if (have_governor_per_policy())
return dbs_data->cdata->attr_group_gov_pol;
else
return dbs_data->cdata->attr_group_gov_sys;
}
void dbs_check_cpu(struct dbs_data *dbs_data, int cpu)
{
struct cpu_dbs_info *cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
struct od_dbs_tuners *od_tuners = dbs_data->tuners;
struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
struct cpufreq_policy *policy = cdbs->shared->policy;
unsigned int sampling_rate;
unsigned int max_load = 0;
unsigned int ignore_nice;
unsigned int j;
if (dbs_data->cdata->governor == GOV_ONDEMAND) {
struct od_cpu_dbs_info_s *od_dbs_info =
dbs_data->cdata->get_cpu_dbs_info_s(cpu);
/*
* Sometimes, the ondemand governor uses an additional
* multiplier to give long delays. So apply this multiplier to
* the 'sampling_rate', so as to keep the wake-up-from-idle
* detection logic a bit conservative.
*/
sampling_rate = od_tuners->sampling_rate;
sampling_rate *= od_dbs_info->rate_mult;
ignore_nice = od_tuners->ignore_nice_load;
} else {
sampling_rate = cs_tuners->sampling_rate;
ignore_nice = cs_tuners->ignore_nice_load;
}
/* Get Absolute Load */
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_info *j_cdbs;
u64 cur_wall_time, cur_idle_time;
unsigned int idle_time, wall_time;
unsigned int load;
int io_busy = 0;
j_cdbs = dbs_data->cdata->get_cpu_cdbs(j);
/*
* For the purpose of ondemand, waiting for disk IO is
* an indication that you're performance critical, and
* not that the system is actually idle. So do not add
* the iowait time to the cpu idle time.
*/
if (dbs_data->cdata->governor == GOV_ONDEMAND)
io_busy = od_tuners->io_is_busy;
cur_idle_time = get_cpu_idle_time(j, &cur_wall_time, io_busy);
wall_time = (unsigned int)
(cur_wall_time - j_cdbs->prev_cpu_wall);
j_cdbs->prev_cpu_wall = cur_wall_time;
idle_time = (unsigned int)
(cur_idle_time - j_cdbs->prev_cpu_idle);
j_cdbs->prev_cpu_idle = cur_idle_time;
if (ignore_nice) {
u64 cur_nice;
unsigned long cur_nice_jiffies;
cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE] -
cdbs->prev_cpu_nice;
/*
* Assumption: nice time between sampling periods will
* be less than 2^32 jiffies for 32 bit sys
*/
cur_nice_jiffies = (unsigned long)
cputime64_to_jiffies64(cur_nice);
cdbs->prev_cpu_nice =
kcpustat_cpu(j).cpustat[CPUTIME_NICE];
idle_time += jiffies_to_usecs(cur_nice_jiffies);
}
if (unlikely(!wall_time || wall_time < idle_time))
continue;
/*
* If the CPU had gone completely idle, and a task just woke up
* on this CPU now, it would be unfair to calculate 'load' the
* usual way for this elapsed time-window, because it will show
* near-zero load, irrespective of how CPU intensive that task
* actually is. This is undesirable for latency-sensitive bursty
* workloads.
*
* To avoid this, we reuse the 'load' from the previous
* time-window and give this task a chance to start with a
* reasonably high CPU frequency. (However, we shouldn't over-do
* this copy, lest we get stuck at a high load (high frequency)
* for too long, even when the current system load has actually
* dropped down. So we perform the copy only once, upon the
* first wake-up from idle.)
*
* Detecting this situation is easy: the governor's deferrable
* timer would not have fired during CPU-idle periods. Hence
* an unusually large 'wall_time' (as compared to the sampling
* rate) indicates this scenario.
*
* prev_load can be zero in two cases and we must recalculate it
* for both cases:
* - during long idle intervals
* - explicitly set to zero
*/
if (unlikely(wall_time > (2 * sampling_rate) &&
j_cdbs->prev_load)) {
load = j_cdbs->prev_load;
/*
* Perform a destructive copy, to ensure that we copy
* the previous load only once, upon the first wake-up
* from idle.
*/
j_cdbs->prev_load = 0;
} else {
load = 100 * (wall_time - idle_time) / wall_time;
j_cdbs->prev_load = load;
}
if (load > max_load)
max_load = load;
}
dbs_data->cdata->gov_check_cpu(cpu, max_load);
}
EXPORT_SYMBOL_GPL(dbs_check_cpu);
void gov_add_timers(struct cpufreq_policy *policy, unsigned int delay)
{
struct dbs_data *dbs_data = policy->governor_data;
struct cpu_dbs_info *cdbs;
int cpu;
for_each_cpu(cpu, policy->cpus) {
cdbs = dbs_data->cdata->get_cpu_cdbs(cpu);
cdbs->timer.expires = jiffies + delay;
add_timer_on(&cdbs->timer, cpu);
}
}
EXPORT_SYMBOL_GPL(gov_add_timers);
static inline void gov_cancel_timers(struct cpufreq_policy *policy)
{
struct dbs_data *dbs_data = policy->governor_data;
struct cpu_dbs_info *cdbs;
int i;
for_each_cpu(i, policy->cpus) {
cdbs = dbs_data->cdata->get_cpu_cdbs(i);
del_timer_sync(&cdbs->timer);
}
}
void gov_cancel_work(struct cpu_common_dbs_info *shared)
{
unsigned long flags;
/*
* No work will be queued from timer handlers after skip_work is
* updated. And so we can safely cancel the work first and then the
* timers.
*/
spin_lock_irqsave(&shared->timer_lock, flags);
shared->skip_work++;
spin_unlock_irqrestore(&shared->timer_lock, flags);
cancel_work_sync(&shared->work);
gov_cancel_timers(shared->policy);
shared->skip_work = 0;
}
EXPORT_SYMBOL_GPL(gov_cancel_work);
/* Will return if we need to evaluate cpu load again or not */
static bool need_load_eval(struct cpu_common_dbs_info *shared,
unsigned int sampling_rate)
{
if (policy_is_shared(shared->policy)) {
ktime_t time_now = ktime_get();
s64 delta_us = ktime_us_delta(time_now, shared->time_stamp);
/* Do nothing if we recently have sampled */
if (delta_us < (s64)(sampling_rate / 2))
return false;
else
shared->time_stamp = time_now;
}
return true;
}
static void dbs_work_handler(struct work_struct *work)
{
struct cpu_common_dbs_info *shared = container_of(work, struct
cpu_common_dbs_info, work);
struct cpufreq_policy *policy;
struct dbs_data *dbs_data;
unsigned int sampling_rate, delay;
unsigned long flags;
bool eval_load;
policy = shared->policy;
dbs_data = policy->governor_data;
/* Kill all timers */
gov_cancel_timers(policy);
if (dbs_data->cdata->governor == GOV_CONSERVATIVE) {
struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
sampling_rate = cs_tuners->sampling_rate;
} else {
struct od_dbs_tuners *od_tuners = dbs_data->tuners;
sampling_rate = od_tuners->sampling_rate;
}
eval_load = need_load_eval(shared, sampling_rate);
/*
* Make sure cpufreq_governor_limits() isn't evaluating load in
* parallel.
*/
mutex_lock(&shared->timer_mutex);
delay = dbs_data->cdata->gov_dbs_timer(policy, eval_load);
mutex_unlock(&shared->timer_mutex);
spin_lock_irqsave(&shared->timer_lock, flags);
shared->skip_work--;
spin_unlock_irqrestore(&shared->timer_lock, flags);
gov_add_timers(policy, delay);
}
static void dbs_timer_handler(unsigned long data)
{
struct cpu_dbs_info *cdbs = (struct cpu_dbs_info *)data;
struct cpu_common_dbs_info *shared = cdbs->shared;
unsigned long flags;
spin_lock_irqsave(&shared->timer_lock, flags);
/*
* Timer handler isn't allowed to queue work at the moment, because:
* - Another timer handler has done that
* - We are stopping the governor
* - Or we are updating the sampling rate of ondemand governor
*/
if (!shared->skip_work) {
shared->skip_work++;
queue_work(system_wq, &shared->work);
}
spin_unlock_irqrestore(&shared->timer_lock, flags);
}
static void set_sampling_rate(struct dbs_data *dbs_data,
unsigned int sampling_rate)
{
if (dbs_data->cdata->governor == GOV_CONSERVATIVE) {
struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
cs_tuners->sampling_rate = sampling_rate;
} else {
struct od_dbs_tuners *od_tuners = dbs_data->tuners;
od_tuners->sampling_rate = sampling_rate;
}
}
static int alloc_common_dbs_info(struct cpufreq_policy *policy,
struct common_dbs_data *cdata)
{
struct cpu_common_dbs_info *shared;
int j;
/* Allocate memory for the common information for policy->cpus */
shared = kzalloc(sizeof(*shared), GFP_KERNEL);
if (!shared)
return -ENOMEM;
/* Set shared for all CPUs, online+offline */
for_each_cpu(j, policy->related_cpus)
cdata->get_cpu_cdbs(j)->shared = shared;
mutex_init(&shared->timer_mutex);
spin_lock_init(&shared->timer_lock);
INIT_WORK(&shared->work, dbs_work_handler);
return 0;
}
static void free_common_dbs_info(struct cpufreq_policy *policy,
struct common_dbs_data *cdata)
{
struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(policy->cpu);
struct cpu_common_dbs_info *shared = cdbs->shared;
int j;
mutex_destroy(&shared->timer_mutex);
for_each_cpu(j, policy->cpus)
cdata->get_cpu_cdbs(j)->shared = NULL;
kfree(shared);
}
static int cpufreq_governor_init(struct cpufreq_policy *policy,
struct dbs_data *dbs_data,
struct common_dbs_data *cdata)
{
unsigned int latency;
int ret;
/* State should be equivalent to EXIT */
if (policy->governor_data)
return -EBUSY;
if (dbs_data) {
if (WARN_ON(have_governor_per_policy()))
return -EINVAL;
ret = alloc_common_dbs_info(policy, cdata);
if (ret)
return ret;
dbs_data->usage_count++;
policy->governor_data = dbs_data;
return 0;
}
dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL);
if (!dbs_data)
return -ENOMEM;
ret = alloc_common_dbs_info(policy, cdata);
if (ret)
goto free_dbs_data;
dbs_data->cdata = cdata;
dbs_data->usage_count = 1;
ret = cdata->init(dbs_data, !policy->governor->initialized);
if (ret)
goto free_common_dbs_info;
/* policy latency is in ns. Convert it to us first */
latency = policy->cpuinfo.transition_latency / 1000;
if (latency == 0)
latency = 1;
/* Bring kernel and HW constraints together */
dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate,
MIN_LATENCY_MULTIPLIER * latency);
set_sampling_rate(dbs_data, max(dbs_data->min_sampling_rate,
latency * LATENCY_MULTIPLIER));
if (!have_governor_per_policy())
cdata->gdbs_data = dbs_data;
ret = sysfs_create_group(get_governor_parent_kobj(policy),
get_sysfs_attr(dbs_data));
if (ret)
goto reset_gdbs_data;
policy->governor_data = dbs_data;
return 0;
reset_gdbs_data:
if (!have_governor_per_policy())
cdata->gdbs_data = NULL;
cdata->exit(dbs_data, !policy->governor->initialized);
free_common_dbs_info:
free_common_dbs_info(policy, cdata);
free_dbs_data:
kfree(dbs_data);
return ret;
}
static int cpufreq_governor_exit(struct cpufreq_policy *policy,
struct dbs_data *dbs_data)
{
struct common_dbs_data *cdata = dbs_data->cdata;
struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(policy->cpu);
/* State should be equivalent to INIT */
if (!cdbs->shared || cdbs->shared->policy)
return -EBUSY;
policy->governor_data = NULL;
if (!--dbs_data->usage_count) {
sysfs_remove_group(get_governor_parent_kobj(policy),
get_sysfs_attr(dbs_data));
if (!have_governor_per_policy())
cdata->gdbs_data = NULL;
cdata->exit(dbs_data, policy->governor->initialized == 1);
kfree(dbs_data);
}
free_common_dbs_info(policy, cdata);
return 0;
}
static int cpufreq_governor_start(struct cpufreq_policy *policy,
struct dbs_data *dbs_data)
{
struct common_dbs_data *cdata = dbs_data->cdata;
unsigned int sampling_rate, ignore_nice, j, cpu = policy->cpu;
struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);
struct cpu_common_dbs_info *shared = cdbs->shared;
int io_busy = 0;
if (!policy->cur)
return -EINVAL;
/* State should be equivalent to INIT */
if (!shared || shared->policy)
return -EBUSY;
if (cdata->governor == GOV_CONSERVATIVE) {
struct cs_dbs_tuners *cs_tuners = dbs_data->tuners;
sampling_rate = cs_tuners->sampling_rate;
ignore_nice = cs_tuners->ignore_nice_load;
} else {
struct od_dbs_tuners *od_tuners = dbs_data->tuners;
sampling_rate = od_tuners->sampling_rate;
ignore_nice = od_tuners->ignore_nice_load;
io_busy = od_tuners->io_is_busy;
}
shared->policy = policy;
shared->time_stamp = ktime_get();
for_each_cpu(j, policy->cpus) {
struct cpu_dbs_info *j_cdbs = cdata->get_cpu_cdbs(j);
unsigned int prev_load;
j_cdbs->prev_cpu_idle =
get_cpu_idle_time(j, &j_cdbs->prev_cpu_wall, io_busy);
prev_load = (unsigned int)(j_cdbs->prev_cpu_wall -
j_cdbs->prev_cpu_idle);
j_cdbs->prev_load = 100 * prev_load /
(unsigned int)j_cdbs->prev_cpu_wall;
if (ignore_nice)
j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE];
__setup_timer(&j_cdbs->timer, dbs_timer_handler,
(unsigned long)j_cdbs,
TIMER_DEFERRABLE | TIMER_IRQSAFE);
}
if (cdata->governor == GOV_CONSERVATIVE) {
struct cs_cpu_dbs_info_s *cs_dbs_info =
cdata->get_cpu_dbs_info_s(cpu);
cs_dbs_info->down_skip = 0;
cs_dbs_info->requested_freq = policy->cur;
} else {
struct od_ops *od_ops = cdata->gov_ops;
struct od_cpu_dbs_info_s *od_dbs_info = cdata->get_cpu_dbs_info_s(cpu);
od_dbs_info->rate_mult = 1;
od_dbs_info->sample_type = OD_NORMAL_SAMPLE;
od_ops->powersave_bias_init_cpu(cpu);
}
gov_add_timers(policy, delay_for_sampling_rate(sampling_rate));
return 0;
}
static int cpufreq_governor_stop(struct cpufreq_policy *policy,
struct dbs_data *dbs_data)
{
struct cpu_dbs_info *cdbs = dbs_data->cdata->get_cpu_cdbs(policy->cpu);
struct cpu_common_dbs_info *shared = cdbs->shared;
/* State should be equivalent to START */
if (!shared || !shared->policy)
return -EBUSY;
gov_cancel_work(shared);
shared->policy = NULL;
return 0;
}
static int cpufreq_governor_limits(struct cpufreq_policy *policy,
struct dbs_data *dbs_data)
{
struct common_dbs_data *cdata = dbs_data->cdata;
unsigned int cpu = policy->cpu;
struct cpu_dbs_info *cdbs = cdata->get_cpu_cdbs(cpu);
/* State should be equivalent to START */
if (!cdbs->shared || !cdbs->shared->policy)
return -EBUSY;
mutex_lock(&cdbs->shared->timer_mutex);
if (policy->max < cdbs->shared->policy->cur)
__cpufreq_driver_target(cdbs->shared->policy, policy->max,
CPUFREQ_RELATION_H);
else if (policy->min > cdbs->shared->policy->cur)
__cpufreq_driver_target(cdbs->shared->policy, policy->min,
CPUFREQ_RELATION_L);
dbs_check_cpu(dbs_data, cpu);
mutex_unlock(&cdbs->shared->timer_mutex);
return 0;
}
int cpufreq_governor_dbs(struct cpufreq_policy *policy,
struct common_dbs_data *cdata, unsigned int event)
{
struct dbs_data *dbs_data;
int ret;
/* Lock governor to block concurrent initialization of governor */
mutex_lock(&cdata->mutex);
if (have_governor_per_policy())
dbs_data = policy->governor_data;
else
dbs_data = cdata->gdbs_data;
if (!dbs_data && (event != CPUFREQ_GOV_POLICY_INIT)) {
ret = -EINVAL;
goto unlock;
}
switch (event) {
case CPUFREQ_GOV_POLICY_INIT:
ret = cpufreq_governor_init(policy, dbs_data, cdata);
break;
case CPUFREQ_GOV_POLICY_EXIT:
ret = cpufreq_governor_exit(policy, dbs_data);
break;
case CPUFREQ_GOV_START:
ret = cpufreq_governor_start(policy, dbs_data);
break;
case CPUFREQ_GOV_STOP:
ret = cpufreq_governor_stop(policy, dbs_data);
break;
case CPUFREQ_GOV_LIMITS:
ret = cpufreq_governor_limits(policy, dbs_data);
break;
default:
ret = -EINVAL;
}
unlock:
mutex_unlock(&cdata->mutex);
return ret;
}
EXPORT_SYMBOL_GPL(cpufreq_governor_dbs);