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 <[email protected]>
--- linux-2.6.16/drivers/cpufreq/cpufreq_conservative.c.orig 2006-03-21 21:27:58.333834500 +0000
+++ linux-2.6.16/drivers/cpufreq/cpufreq_conservative.c 2006-03-21 21:28:53.969311500 +0000
@@ -294,31 +294,40 @@
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 @@
/* 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 @@
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;
- }
+ this_dbs_info->prev_cpu_idle_down =
+ this_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 @@
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;
+ /* 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;
- 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 @@
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;
}
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