Skip to content

Commit

Permalink
[CPUFREQ] Remove slowdown from ondemand sampling path.
Browse files Browse the repository at this point in the history 
Remove slowdown from ondemand sampling path. This reduces the code path length
in dbs_check_cpu() by half. slowdown was not used by ondemand by default.
If there are any user level tools that were using this tunable, they
may report error now.

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>
  • Loading branch information
Venkatesh Pallipadi authored and Dave Jones committed Jun 30, 2006
1 parent 501b7c7 commit ccb2fe2
Show file tree
Hide file tree
Showing 2 changed files with 42 additions and 98 deletions.
138 changes: 40 additions & 98 deletions drivers/cpufreq/cpufreq_ondemand.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,16 +56,14 @@ static unsigned int def_sampling_rate;
#define MIN_SAMPLING_RATE (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
#define MAX_SAMPLING_RATE (500 * def_sampling_rate)
#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
#define DEF_SAMPLING_DOWN_FACTOR (1)
#define MAX_SAMPLING_DOWN_FACTOR (10)
#define TRANSITION_LATENCY_LIMIT (10 * 1000)

static void do_dbs_timer(void *data);

struct cpu_dbs_info_s {
cputime64_t prev_cpu_idle;
cputime64_t prev_cpu_wall;
struct cpufreq_policy *cur_policy;
unsigned int prev_cpu_idle_up;
unsigned int prev_cpu_idle_down;
unsigned int enable;
};
static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
Expand All @@ -87,24 +85,26 @@ static struct workqueue_struct *dbs_workq;

struct dbs_tuners {
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int ignore_nice;
};

static struct dbs_tuners dbs_tuners_ins = {
.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
.sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
.ignore_nice = 0,
};

static inline unsigned int get_cpu_idle_time(unsigned int cpu)
static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
{
return kstat_cpu(cpu).cpustat.idle +
kstat_cpu(cpu).cpustat.iowait +
( dbs_tuners_ins.ignore_nice ?
kstat_cpu(cpu).cpustat.nice :
0);
cputime64_t retval;

retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
kstat_cpu(cpu).cpustat.iowait);

if (dbs_tuners_ins.ignore_nice)
retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);

return retval;
}

/************************** sysfs interface ************************/
Expand Down Expand Up @@ -133,29 +133,9 @@ static ssize_t show_##file_name \
return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
}
show_one(sampling_rate, sampling_rate);
show_one(sampling_down_factor, sampling_down_factor);
show_one(up_threshold, up_threshold);
show_one(ignore_nice_load, ignore_nice);

static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
unsigned int input;
int ret;
ret = sscanf (buf, "%u", &input);
if (ret != 1 )
return -EINVAL;

if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
return -EINVAL;

mutex_lock(&dbs_mutex);
dbs_tuners_ins.sampling_down_factor = input;
mutex_unlock(&dbs_mutex);

return count;
}

static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
const char *buf, size_t count)
{
Expand Down Expand Up @@ -217,12 +197,12 @@ static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
}
dbs_tuners_ins.ignore_nice = input;

/* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
/* we need to re-evaluate prev_cpu_idle */
for_each_online_cpu(j) {
struct cpu_dbs_info_s *j_dbs_info;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
struct cpu_dbs_info_s *dbs_info;
dbs_info = &per_cpu(cpu_dbs_info, j);
dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
dbs_info->prev_cpu_wall = get_jiffies_64();
}
mutex_unlock(&dbs_mutex);

Expand All @@ -234,15 +214,13 @@ static struct freq_attr _name = \
__ATTR(_name, 0644, show_##_name, store_##_name)

define_one_rw(sampling_rate);
define_one_rw(sampling_down_factor);
define_one_rw(up_threshold);
define_one_rw(ignore_nice_load);

static struct attribute * dbs_attributes[] = {
&sampling_rate_max.attr,
&sampling_rate_min.attr,
&sampling_rate.attr,
&sampling_down_factor.attr,
&up_threshold.attr,
&ignore_nice_load.attr,
NULL
Expand All @@ -257,11 +235,10 @@ static struct attribute_group dbs_attr_group = {

static void dbs_check_cpu(int cpu)
{
unsigned int idle_ticks, up_idle_ticks, total_ticks;
unsigned int freq_next;
unsigned int freq_down_sampling_rate;
static int down_skip[NR_CPUS];
unsigned int idle_ticks, total_ticks;
unsigned int load;
struct cpu_dbs_info_s *this_dbs_info;
cputime64_t cur_jiffies;

struct cpufreq_policy *policy;
unsigned int j;
Expand All @@ -271,10 +248,14 @@ static void dbs_check_cpu(int cpu)
return;

policy = this_dbs_info->cur_policy;
cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
this_dbs_info->prev_cpu_wall);
this_dbs_info->prev_cpu_wall = cur_jiffies;
/*
* Every sampling_rate, we check, if current idle time is less
* than 20% (default), then we try to increase frequency
* Every sampling_rate*sampling_down_factor, we look for a the lowest
* Every sampling_rate, we look for a the lowest
* frequency which can sustain the load while keeping idle time over
* 30%. If such a frequency exist, we try to decrease to this frequency.
*
Expand All @@ -283,36 +264,26 @@ static void dbs_check_cpu(int cpu)
* 5% (default) of current frequency
*/

/* Check for frequency increase */
/* Get Idle Time */
idle_ticks = UINT_MAX;
for_each_cpu_mask(j, policy->cpus) {
unsigned int tmp_idle_ticks, total_idle_ticks;
cputime64_t total_idle_ticks;
unsigned int tmp_idle_ticks;
struct cpu_dbs_info_s *j_dbs_info;

j_dbs_info = &per_cpu(cpu_dbs_info, j);
total_idle_ticks = get_cpu_idle_time(j);
tmp_idle_ticks = total_idle_ticks -
j_dbs_info->prev_cpu_idle_up;
j_dbs_info->prev_cpu_idle_up = total_idle_ticks;
tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
j_dbs_info->prev_cpu_idle);
j_dbs_info->prev_cpu_idle = total_idle_ticks;

if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}
load = (100 * (total_ticks - idle_ticks)) / total_ticks;

/* Scale idle ticks by 100 and compare with up and down ticks */
idle_ticks *= 100;
up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
usecs_to_jiffies(dbs_tuners_ins.sampling_rate);

if (idle_ticks < up_idle_ticks) {
down_skip[cpu] = 0;
for_each_cpu_mask(j, policy->cpus) {
struct cpu_dbs_info_s *j_dbs_info;

j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->prev_cpu_idle_down =
j_dbs_info->prev_cpu_idle_up;
}
/* Check for frequency increase */
if (load > dbs_tuners_ins.up_threshold) {
/* if we are already at full speed then break out early */
if (policy->cur == policy->max)
return;
Expand All @@ -323,50 +294,22 @@ static void dbs_check_cpu(int cpu)
}

/* Check for frequency decrease */
down_skip[cpu]++;
if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor)
return;

idle_ticks = UINT_MAX;
for_each_cpu_mask(j, policy->cpus) {
unsigned int tmp_idle_ticks, total_idle_ticks;
struct cpu_dbs_info_s *j_dbs_info;

j_dbs_info = &per_cpu(cpu_dbs_info, j);
/* Check for frequency decrease */
total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
tmp_idle_ticks = total_idle_ticks -
j_dbs_info->prev_cpu_idle_down;
j_dbs_info->prev_cpu_idle_down = total_idle_ticks;

if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}

down_skip[cpu] = 0;
/* if we cannot reduce the frequency anymore, break out early */
if (policy->cur == policy->min)
return;

/* Compute how many ticks there are between two measurements */
freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
dbs_tuners_ins.sampling_down_factor;
total_ticks = usecs_to_jiffies(freq_down_sampling_rate);

/*
* The optimal frequency is the frequency that is the lowest that
* can support the current CPU usage without triggering the up
* policy. To be safe, we focus 10 points under the threshold.
*/
freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;
freq_next = (freq_next * policy->cur) /
if (load < (dbs_tuners_ins.up_threshold - 10)) {
unsigned int freq_next;
freq_next = (policy->cur * load) /
(dbs_tuners_ins.up_threshold - 10);

if (freq_next < policy->min)
freq_next = policy->min;

if (freq_next <= ((policy->cur * 95) / 100))
__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);
}
}

static void do_dbs_timer(void *data)
Expand Down Expand Up @@ -432,9 +375,8 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->cur_policy = policy;

j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_idle_down
= j_dbs_info->prev_cpu_idle_up;
j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
j_dbs_info->prev_cpu_wall = get_jiffies_64();
}
this_dbs_info->enable = 1;
sysfs_create_group(&policy->kobj, &dbs_attr_group);
Expand Down
2 changes: 2 additions & 0 deletions include/asm-generic/cputime.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,7 +24,9 @@ typedef u64 cputime64_t;

#define cputime64_zero (0ULL)
#define cputime64_add(__a, __b) ((__a) + (__b))
#define cputime64_sub(__a, __b) ((__a) - (__b))
#define cputime64_to_jiffies64(__ct) (__ct)
#define jiffies64_to_cputime64(__jif) (__jif)
#define cputime_to_cputime64(__ct) ((u64) __ct)


Expand Down

0 comments on commit ccb2fe2

Please sign in to comment.