From ed12978453a3845c947695e7ad32bb3ede444813 Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Wed, 4 Feb 2009 01:17:41 +0100 Subject: [CPUFREQ] Introduce /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_transition_latency It's not only useful for the ondemand and conservative governors, but also for userspace daemons to know about the HW transition latency of the CPU. It is especially useful for userspace to know about this value when the ondemand or conservative governors are run. The sampling rate control value depends on it and for userspace being able to set sane tuning values there it has to know about the transition latency. Signed-off-by: Thomas Renninger Signed-off-by: Dave Jones --- Documentation/cpu-freq/user-guide.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation') diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt index 917918f84fc..75f41193f3e 100644 --- a/Documentation/cpu-freq/user-guide.txt +++ b/Documentation/cpu-freq/user-guide.txt @@ -152,6 +152,18 @@ cpuinfo_min_freq : this file shows the minimum operating frequency the processor can run at(in kHz) cpuinfo_max_freq : this file shows the maximum operating frequency the processor can run at(in kHz) +cpuinfo_transition_latency The time it takes on this CPU to + switch between two frequencies in nano + seconds. If unknown or known to be + that high that the driver does not + work with the ondemand governor, -1 + (CPUFREQ_ETERNAL) will be returned. + Using this information can be useful + to choose an appropriate polling + frequency for a kernel governor or + userspace daemon. Make sure to not + switch the frequency too often + resulting in performance loss. scaling_driver : this file shows what cpufreq driver is used to set the frequency on this CPU -- cgit v1.2.3-70-g09d2 From 9411b4ef7fcb534fe1582fe02738254e398dd931 Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Wed, 4 Feb 2009 11:54:04 +0100 Subject: [CPUFREQ] ondemand/conservative: deprecate sampling_rate{min,max} The same info can be obtained via the transition_latency sysfs file Signed-off-by: Thomas Renninger Signed-off-by: Dave Jones --- Documentation/cpu-freq/governors.txt | 10 ++++++++-- drivers/cpufreq/cpufreq_conservative.c | 15 +++++++++++++++ drivers/cpufreq/cpufreq_ondemand.c | 17 +++++++++++++++++ 3 files changed, 40 insertions(+), 2 deletions(-) (limited to 'Documentation') diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index 5b0cfa67aff..9b1851297d4 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -119,8 +119,14 @@ 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. -show_sampling_rate_(min|max): the minimum and maximum sampling rates -available that you may set 'sampling_rate' to. +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). 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 diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c index c6b3c6a02fc..0912d7ca8cd 100644 --- a/drivers/cpufreq/cpufreq_conservative.c +++ b/drivers/cpufreq/cpufreq_conservative.c @@ -140,11 +140,26 @@ 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; + } return sprintf(buf, "%u\n", MAX_SAMPLING_RATE); } 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); } diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c index 1fa4420eb33..32ddeaa4224 100644 --- a/drivers/cpufreq/cpufreq_ondemand.c +++ b/drivers/cpufreq/cpufreq_ondemand.c @@ -21,6 +21,7 @@ #include #include #include +#include /* * dbs is used in this file as a shortform for demandbased switching @@ -203,11 +204,27 @@ 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; + } return sprintf(buf, "%u\n", MAX_SAMPLING_RATE); } 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); } -- cgit v1.2.3-70-g09d2 From 112124ab0a9f507a0d7fdbb1e1ed2b9a24f8c4ea Mon Sep 17 00:00:00 2001 From: Thomas Renninger Date: Wed, 4 Feb 2009 11:55:12 +0100 Subject: [CPUFREQ] ondemand/conservative: sanitize sampling_rate restrictions Limit sampling rate to transition_latency * 100 or kernel limits. If sampling_rate is tried to be set too low, set the lowest allowed value. Signed-off-by: Thomas Renninger Signed-off-by: Dave Jones --- Documentation/cpu-freq/governors.txt | 14 +++++++++++++- drivers/cpufreq/cpufreq_conservative.c | 28 ++++++++++++++++++---------- drivers/cpufreq/cpufreq_ondemand.c | 28 ++++++++++++++++++---------- 3 files changed, 49 insertions(+), 21 deletions(-) (limited to 'Documentation') diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index 9b1851297d4..ce73f3eb5dd 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -117,7 +117,19 @@ accessible parameters: sampling_rate: measured in uS (10^-6 seconds), this is how often you 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. +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 +To set the sampling rate 750 times as high as the transition latency +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 diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c index 0912d7ca8cd..8d541c69aec 100644 --- a/drivers/cpufreq/cpufreq_conservative.c +++ b/drivers/cpufreq/cpufreq_conservative.c @@ -54,8 +54,20 @@ static unsigned int def_sampling_rate; (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10)) #define MIN_SAMPLING_RATE \ (def_sampling_rate / MIN_SAMPLING_RATE_RATIO) +/* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon + * Define the minimal settable sampling rate to the greater of: + * - "HW transition latency" * 100 (same as default sampling / 10) + * - MIN_STAT_SAMPLING_RATE + * To avoid that userspace shoots itself. +*/ +static unsigned int minimum_sampling_rate(void) +{ + return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE); +} + +/* This will also vanish soon with removing sampling_rate_max */ #define MAX_SAMPLING_RATE (500 * def_sampling_rate) -#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) +#define LATENCY_MULTIPLIER (1000) #define DEF_SAMPLING_DOWN_FACTOR (1) #define MAX_SAMPLING_DOWN_FACTOR (10) #define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000) @@ -208,13 +220,11 @@ static ssize_t store_sampling_rate(struct cpufreq_policy *unused, ret = sscanf(buf, "%u", &input); mutex_lock(&dbs_mutex); - if (ret != 1 || input > MAX_SAMPLING_RATE || - input < MIN_SAMPLING_RATE) { + if (ret != 1) { mutex_unlock(&dbs_mutex); return -EINVAL; } - - dbs_tuners_ins.sampling_rate = input; + dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate()); mutex_unlock(&dbs_mutex); return count; @@ -540,11 +550,9 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, if (latency == 0) latency = 1; - def_sampling_rate = 10 * latency * - DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; - - if (def_sampling_rate < MIN_STAT_SAMPLING_RATE) - def_sampling_rate = MIN_STAT_SAMPLING_RATE; + def_sampling_rate = + max(10 * latency * LATENCY_MULTIPLIER, + MIN_STAT_SAMPLING_RATE); dbs_tuners_ins.sampling_rate = def_sampling_rate; diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c index 32ddeaa4224..338f428a15b 100644 --- a/drivers/cpufreq/cpufreq_ondemand.c +++ b/drivers/cpufreq/cpufreq_ondemand.c @@ -52,8 +52,20 @@ static unsigned int def_sampling_rate; (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10)) #define MIN_SAMPLING_RATE \ (def_sampling_rate / MIN_SAMPLING_RATE_RATIO) +/* Above MIN_SAMPLING_RATE will vanish with its sysfs file soon + * Define the minimal settable sampling rate to the greater of: + * - "HW transition latency" * 100 (same as default sampling / 10) + * - MIN_STAT_SAMPLING_RATE + * To avoid that userspace shoots itself. +*/ +static unsigned int minimum_sampling_rate(void) +{ + return max(def_sampling_rate / 10, MIN_STAT_SAMPLING_RATE); +} + +/* This will also vanish soon with removing sampling_rate_max */ #define MAX_SAMPLING_RATE (500 * def_sampling_rate) -#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) +#define LATENCY_MULTIPLIER (1000) #define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000) static void do_dbs_timer(struct work_struct *work); @@ -255,13 +267,11 @@ static ssize_t store_sampling_rate(struct cpufreq_policy *unused, ret = sscanf(buf, "%u", &input); mutex_lock(&dbs_mutex); - if (ret != 1 || input > MAX_SAMPLING_RATE - || input < MIN_SAMPLING_RATE) { + if (ret != 1) { mutex_unlock(&dbs_mutex); return -EINVAL; } - - dbs_tuners_ins.sampling_rate = input; + dbs_tuners_ins.sampling_rate = max(input, minimum_sampling_rate()); mutex_unlock(&dbs_mutex); return count; @@ -607,11 +617,9 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy, if (latency == 0) latency = 1; - def_sampling_rate = latency * - DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; - - if (def_sampling_rate < MIN_STAT_SAMPLING_RATE) - def_sampling_rate = MIN_STAT_SAMPLING_RATE; + def_sampling_rate = + max(latency * LATENCY_MULTIPLIER, + MIN_STAT_SAMPLING_RATE); dbs_tuners_ins.sampling_rate = def_sampling_rate; } -- cgit v1.2.3-70-g09d2