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Commit 4f4d1ad6 authored by Thomas Renninger's avatar Thomas Renninger Committed by Dave Jones
Browse files

[CPUFREQ] Only set sampling_rate_max deprecated, sampling_rate_min is useful 



Update the documentation accordingly.
Cleanup and use printk_once.

Signed-off-by: default avatarThomas Renninger <trenn@suse.de>
Signed-off-by: default avatarDave Jones <davej@redhat.com>
parent 86e13684

Documentation/cpu-freq/governors.txt

+14 −12
Original line number Diff line number Diff line
@@ -119,10 +119,6 @@ want the kernel to look at the CPU usage and to make decisions on 
what to do about the frequency.  Typically this is set to values of

around '10000' or more. It's default value is (cmp. with users-guide.txt):

transition_latency * 1000

The lowest value you can set is:

transition_latency * 100 or it may get restricted to a value where it

makes not sense for the kernel anymore to poll that often which depends

on your HZ config variable (HZ=1000: max=20000us, HZ=250: max=5000).

Be aware that transition latency is in ns and sampling_rate is in us, so you

get the same sysfs value by default.

Sampling rate should always get adjusted considering the transition latency
@@ -131,14 +127,20 @@ in the bash (as said, 1000 is default), do: 
echo `$(($(cat cpuinfo_transition_latency) * 750 / 1000)) \

    >ondemand/sampling_rate



show_sampling_rate_(min|max): THIS INTERFACE IS DEPRECATED, DON'T USE IT.

You can use wider ranges now and the general

cpuinfo_transition_latency variable (cmp. with user-guide.txt) can be

used to obtain exactly the same info:

show_sampling_rate_min = transtition_latency * 500    / 1000

show_sampling_rate_max = transtition_latency * 500000 / 1000

(divided by 1000 is to illustrate that sampling rate is in us and

transition latency is exported ns).

show_sampling_rate_min:

The sampling rate is limited by the HW transition latency:

transition_latency * 100

Or by kernel restrictions:

If CONFIG_NO_HZ is set, the limit is 10ms fixed.

If CONFIG_NO_HZ is not set or no_hz=off boot parameter is used, the

limits depend on the CONFIG_HZ option:

HZ=1000: min=20000us  (20ms)

HZ=250:  min=80000us  (80ms)

HZ=100:  min=200000us (200ms)

The highest value of kernel and HW latency restrictions is shown and

used as the minimum sampling rate.



show_sampling_rate_max: THIS INTERFACE IS DEPRECATED, DON'T USE IT.



up_threshold: defines what the average CPU usage between the samplings

of 'sampling_rate' needs to be for the kernel to make a decision on

drivers/cpufreq/cpufreq_conservative.c

+2 −15
Original line number Diff line number Diff line
@@ -167,26 +167,13 @@ static struct notifier_block dbs_cpufreq_notifier_block = { 
/************************** sysfs interface ************************/

static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)

{

	static int print_once;



	if (!print_once) {

		printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "

		       "sysfs file is deprecated - used by: %s\n",

		       current->comm);

		print_once = 1;

	}

	printk_once(KERN_INFO "CPUFREQ: conservative sampling_rate_max "

		    "sysfs file is deprecated - used by: %s\n", current->comm);

	return sprintf(buf, "%u\n", -1U);

}



static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)

{

	static int print_once;



	if (!print_once) {

		printk(KERN_INFO "CPUFREQ: conservative sampling_rate_max "

		       "sysfs file is deprecated - used by: %s\n", current->comm);

		print_once = 1;

	}

	return sprintf(buf, "%u\n", min_sampling_rate);

}

drivers/cpufreq/cpufreq_ondemand.c

+2 −16
Original line number Diff line number Diff line
@@ -205,27 +205,13 @@ static void ondemand_powersave_bias_init(void) 
/************************** sysfs interface ************************/

static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)

{

	static int print_once;



	if (!print_once) {

		printk(KERN_INFO "CPUFREQ: ondemand sampling_rate_max "

		       "sysfs file is deprecated - used by: %s\n",

		       current->comm);

		print_once = 1;

	}

	printk_once(KERN_INFO "CPUFREQ: ondemand sampling_rate_max "

	       "sysfs file is deprecated - used by: %s\n", current->comm);

	return sprintf(buf, "%u\n", -1U);

}



static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)

{

	static int print_once;



	if (!print_once) {

		printk(KERN_INFO "CPUFREQ: ondemand sampling_rate_min "

		       "sysfs file is deprecated - used by: %s\n",

		       current->comm);

		print_once = 1;

	}

	return sprintf(buf, "%u\n", min_sampling_rate);

}