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[PATCH] cpufreq_conservative: make for_each_cpu() safe

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All these changes should make cpufreq_conservative safe in regards to the x86
for_each_cpu cpumask.h changes and whatnot.

Whilst making it safe a number of pointless for loops related to the cpu
mask's were removed.  I was never comfortable with all those for loops,
especially as the iteration is over the same data again and again for each
CPU you had in a single poll, an O(n^2) outcome to frequency scaling.

The approach I use is to assume by default no CPU's exist and it sets the
requested_freq to zero as a kind of flag, the reasoning is in the source ;)
If the CPU is queried and requested_freq is zero then it initialises the
variable to current_freq and then continues as if nothing happened which
should be the same net effect as before?

Signed-off-by: Alexander Clouter <alex-kernel@digriz.org.uk>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
This commit is contained in:
Alexander Clouter 2006-03-22 09:59:16 +00:00 committed by Dominik Brodowski
parent e8a0257225
commit 08a28e2e98
1 changed files with 41 additions and 48 deletions
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89
drivers/cpufreq/cpufreq_conservative.c
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@ -294,31 +294,40 @@ static struct attribute_group dbs_attr_group = {
static void dbs_check_cpu(int cpu)
{
unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
unsigned int tmp_idle_ticks, total_idle_ticks;
unsigned int freq_step;
unsigned int freq_down_sampling_rate;
static int down_skip[NR_CPUS];
static int requested_freq[NR_CPUS];
static unsigned short init_flag = 0;
struct cpu_dbs_info_s *this_dbs_info;
struct cpu_dbs_info_s *dbs_info;
static unsigned short down_skip[NR_CPUS];
static unsigned int requested_freq[NR_CPUS];
static unsigned int init_flag = NR_CPUS;
struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
struct cpufreq_policy *policy;
unsigned int j;
this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
if (!this_dbs_info->enable)
return;
policy = this_dbs_info->cur_policy;
if ( init_flag == 0 ) {
for_each_online_cpu(j) {
dbs_info = &per_cpu(cpu_dbs_info, j);
requested_freq[j] = dbs_info->cur_policy->cur;
if ( init_flag != 0 ) {
for_each_cpu(init_flag) {
down_skip[init_flag] = 0;
/* I doubt a CPU exists with a freq of 0hz :) */
requested_freq[init_flag] = 0;
}
init_flag = 1;
init_flag = 0;
}
/*
* If its a freshly initialised cpu we setup requested_freq. This
* check could be avoided if we did not care about a first time
* stunted increase in CPU speed when there is a load. I feel we
* should be initialising this to something. The removal of a CPU
* is not a problem, after a short time the CPU should settle down
* to a 'natural' frequency.
*/
if (requested_freq[cpu] == 0)
requested_freq[cpu] = this_dbs_info->cur_policy->cur;
policy = this_dbs_info->cur_policy;
/*
* The default safe range is 20% to 80%
* Every sampling_rate, we check
@ -335,20 +344,15 @@ static void dbs_check_cpu(int cpu)
/* Check for frequency increase */
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 increase */
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;
/* Check for frequency increase */
total_idle_ticks = get_cpu_idle_time(cpu);
tmp_idle_ticks = total_idle_ticks -
this_dbs_info->prev_cpu_idle_up;
this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
}
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
/* Scale idle ticks by 100 and compare with up and down ticks */
idle_ticks *= 100;
@ -357,13 +361,9 @@ static void dbs_check_cpu(int cpu)
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;
this_dbs_info->prev_cpu_idle_down =
this_dbs_info->prev_cpu_idle_up;
j_dbs_info = &per_cpu(cpu_dbs_info, j);
j_dbs_info->prev_cpu_idle_down =
j_dbs_info->prev_cpu_idle_up;
}
/* if we are already at full speed then break out early */
if (requested_freq[cpu] == policy->max)
return;
@ -388,21 +388,14 @@ static void dbs_check_cpu(int 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;
/* Check for frequency decrease */
total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
tmp_idle_ticks = total_idle_ticks -
this_dbs_info->prev_cpu_idle_down;
this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
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;
}
if (tmp_idle_ticks < idle_ticks)
idle_ticks = tmp_idle_ticks;
/* Scale idle ticks by 100 and compare with up and down ticks */
idle_ticks *= 100;
@ -491,7 +484,7 @@ 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_up = get_cpu_idle_time(cpu);
j_dbs_info->prev_cpu_idle_down
= j_dbs_info->prev_cpu_idle_up;
}