[PATCH] 2/3 A dynamic cpufreq governor

[Pallipadi, Venkatesh]

ondemand2.patch - basic cpufreq_ondemand governor, with some changes 
since the last time.

diffstat ondemand2.patch
 Kconfig            |   15 +++
 Makefile           |    1 
 cpufreq_ondemand.c |  236
+++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 252 insertions(+)


diff -purN linux-2.6.0-test8/drivers/cpufreq/cpufreq_ondemand.c
linux-2.6.0-test8-dbs/drivers/cpufreq/cpufreq_ondemand.c
--- linux-2.6.0-test8/drivers/cpufreq/cpufreq_ondemand.c
1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.0-test8-dbs/drivers/cpufreq/cpufreq_ondemand.c
2003-10-25 13:38:27.000000000 -0700
@@ -0,0 +1,236 @@
+/*
+ *  drivers/cpufreq/cpufreq_ondemand.c
+ *
+ *  Copyright (C)  2001 Russell King
+ *            (C)  2003 Venkatesh Pallipadi
<venkatesh.pallipadi@xxxxxxxxx>.
+ *                      Jun Nakajima <jun.nakajima@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/smp.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ctype.h>
+#include <linux/cpufreq.h>
+#include <linux/sysctl.h>
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/sysfs.h>
+#include <linux/sched.h>
+#include <linux/kmod.h>
+#include <linux/workqueue.h>
+#include <linux/jiffies.h>
+#include <linux/config.h>
+#include <linux/kernel_stat.h>
+
+/*
+ * dbs is used in this file as a shortform for demandbased switching
+ * It helps to keep variable names smaller, simpler
+ */
+
+#define DEF_SAMPLING_RATE			(HZ/4)	/* 250ms */
+#define MIN_SAMPLING_RATE			(HZ/10)
+#define MAX_SAMPLING_RATE			(10*HZ)
+
+#define DEF_FREQUENCY_UP_THRESHOLD		(80)
+#define MIN_FREQUENCY_UP_THRESHOLD		(0)
+#define MAX_FREQUENCY_UP_THRESHOLD		(100)
+
+#define DEF_FREQUENCY_DOWN_THRESHOLD		(20)
+#define MIN_FREQUENCY_DOWN_THRESHOLD		(0)
+#define MAX_FREQUENCY_DOWN_THRESHOLD		(100)
+
+#define LOW_LATENCY_FREQUENCY_CHANGE_LIMIT 	(100*1000) /* in nS */
+
+static void do_dbs_timer(void *data);
+
+typedef struct {
+	struct cpufreq_policy 	*cur_policy;
+	unsigned int 		prev_cpu_idle;
+	unsigned int 		enable;
+} ____cacheline_aligned cpu_dbs_info_t;
+static cpu_dbs_info_t cpu_dbs_info[NR_CPUS];
+
+static unsigned int dbs_enable;	/* number of CPUs using this
policy */
+
+static DECLARE_MUTEX 	(dbs_sem);
+static DECLARE_WORK	(dbs_work, do_dbs_timer, NULL);
+
+struct dbs_tuners {
+	unsigned int 		sampling_rate;
+	unsigned int		up_threshold;
+	unsigned int		down_threshold;
+};
+
+struct dbs_tuners dbs_tuners_ins = {
+	.sampling_rate = DEF_SAMPLING_RATE,
+	.up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
+	.down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD,
+};
+
+static void dbs_check_cpu(int cpu)
+{
+	unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
+
+	if (!cpu_dbs_info[cpu].enable)
+		return;
+
+	idle_ticks = kstat_cpu(cpu).cpustat.idle - 
+		cpu_dbs_info[cpu].prev_cpu_idle;
+	cpu_dbs_info[cpu].prev_cpu_idle = kstat_cpu(cpu).cpustat.idle;
+
+	/* 
+	 * The default safe range is 20% to 80% 
+	 * - If current idle time is less than 20%, then we try to 
+	 * increase frequency
+	 * - If current idle time is more than 80%, then we try to
+	 * decrease frequency
+	 */
+	up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
+			dbs_tuners_ins.sampling_rate / 100;
+
+	if (idle_ticks < up_idle_ticks) {
+		cpufreq_driver_target(cpu_dbs_info[cpu].cur_policy,
+			cpu_dbs_info[cpu].cur_policy->cur + 1, 
+			CPUFREQ_RELATION_L);
+		return;
+	}
+
+	down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
+			dbs_tuners_ins.sampling_rate / 100;
+
+	if (idle_ticks > down_idle_ticks ) {
+		cpufreq_driver_target(cpu_dbs_info[cpu].cur_policy,
+			cpu_dbs_info[cpu].cur_policy->cur - 1, 
+			CPUFREQ_RELATION_H);
+		return;
+	}
+}
+
+static void do_dbs_timer(void *data)
+{ 
+	int i;
+	down(&dbs_sem);
+	for (i = 0; i < NR_CPUS; i++)
+		if (cpu_online(i))
+			dbs_check_cpu(i);
+	schedule_delayed_work(&dbs_work, dbs_tuners_ins.sampling_rate); 
+	up(&dbs_sem);
+} 
+
+
+static inline void dbs_timer_init(void)
+{
+	INIT_WORK(&dbs_work, do_dbs_timer, NULL);
+	schedule_work(&dbs_work);
+	return;
+}
+
+static inline void dbs_timer_exit(void)
+{
+	cancel_delayed_work(&dbs_work);
+	return;
+}
+
+static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
+				   unsigned int event)
+{
+	unsigned int cpu = policy->cpu;
+
+	switch (event) {
+	case CPUFREQ_GOV_START:
+		if ((!cpu_online(cpu)) || !policy->cur)
+			return -EINVAL;
+		if (policy->cpuinfo.transition_latency > 
+				LOW_LATENCY_FREQUENCY_CHANGE_LIMIT)
+			return -EINVAL;
+		if (cpu_dbs_info[cpu].enable) /* Already enabled */
+			break;
+
+		printk(KERN_DEBUG 
+			"ONDEMAND START: cpu %d, max %d, min %d, cur
%d\n",
+			policy->cpu, policy->max, policy->min,
policy->cur);
+		down(&dbs_sem);
+		cpu_dbs_info[cpu].cur_policy = policy;
+		cpu_dbs_info[cpu].prev_cpu_idle = 
+				kstat_cpu(cpu).cpustat.idle;
+		cpu_dbs_info[cpu].enable = 1;
+		dbs_enable++;
+		/*
+		 * Start the timerschedule work, when this governor
+		 * is used for first time
+		 */
+		if (dbs_enable == 1)
+			dbs_timer_init();
+		
+		up(&dbs_sem);
+		break;
+
+	case CPUFREQ_GOV_STOP:
+		printk(KERN_DEBUG 
+			"ONDEMAND STOP: cpu %d, max %d, min %d, cur
%d\n",
+			policy->cpu, policy->max, policy->min,
policy->cur);
+		down(&dbs_sem);
+		cpu_dbs_info[cpu].enable = 0;
+		dbs_enable--;
+		/*
+		 * Stop the timerschedule work, when this governor
+		 * is used for first time
+		 */
+		if (dbs_enable == 0) 
+			dbs_timer_exit();
+		
+		up(&dbs_sem);
+		break;
+
+	case CPUFREQ_GOV_LIMITS:
+		printk(KERN_DEBUG 
+			"ONDEMAND LIMIT: cpu %d, max %d, min %d, cur
%d\n",
+			policy->cpu, policy->max, policy->min,
policy->cur);
+		down(&dbs_sem);
+		if (policy->max < cpu_dbs_info[cpu].cur_policy->cur)
+			__cpufreq_driver_target(
+					cpu_dbs_info[cpu].cur_policy,
+				       	policy->max,
CPUFREQ_RELATION_H);
+		else if (policy->min >
cpu_dbs_info[cpu].cur_policy->cur)
+			__cpufreq_driver_target(
+					cpu_dbs_info[cpu].cur_policy,
+				       	policy->min,
CPUFREQ_RELATION_L);
+		up(&dbs_sem);
+		break;
+	}
+	return 0;
+}
+
+struct cpufreq_governor cpufreq_gov_dbs = {
+	.name		= "ondemand",
+	.governor	= cpufreq_governor_dbs,
+	.owner		= THIS_MODULE,
+};
+EXPORT_SYMBOL(cpufreq_gov_dbs);
+
+static int __init cpufreq_gov_dbs_init(void)
+{
+	return cpufreq_register_governor(&cpufreq_gov_dbs);
+}
+
+static void __exit cpufreq_gov_dbs_exit(void)
+{
+	/* Make sure that the scheduled work is indeed not running */
+	flush_scheduled_work();
+	cpufreq_unregister_governor(&cpufreq_gov_dbs);
+}
+
+
+MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@xxxxxxxxx>");
+MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor
for "
+		"Low Latency Frequency Transition capable processors");
+MODULE_LICENSE ("GPL");
+
+module_init(cpufreq_gov_dbs_init);
+module_exit(cpufreq_gov_dbs_exit);
diff -purN linux-2.6.0-test8/drivers/cpufreq/Kconfig
linux-2.6.0-test8-dbs/drivers/cpufreq/Kconfig
--- linux-2.6.0-test8/drivers/cpufreq/Kconfig	2003-10-17
14:43:29.000000000 -0700
+++ linux-2.6.0-test8-dbs/drivers/cpufreq/Kconfig	2003-10-25
13:34:09.000000000 -0700
@@ -68,6 +68,21 @@ config CPU_FREQ_GOV_USERSPACE
 
 	  If in doubt, say Y.
 
+config CPU_FREQ_GOV_ONDEMAND
+	tristate "'ondemand' cpufreq policy governor"
+	depends on CPU_FREQ
+	help
+	  'ondemand' - This driver adds a dynamic cpufreq policy
governor.
+	  The governor does a periodic polling and 
+	  changes frequency based on the CPU utilization.
+	  The support for this governor depends on CPU capability to
+	  do fast frequency switching (i.e, very low latency frequency
+	  transitions). 
+
+	  For details, take a look at linux/Documentation/cpu-freq.
+
+	  If in doubt, say N.
+
 config CPU_FREQ_24_API
 	bool "/proc/sys/cpu/ interface (2.4. / OLD)"
 	depends on CPU_FREQ && SYSCTL && CPU_FREQ_GOV_USERSPACE
diff -purN linux-2.6.0-test8/drivers/cpufreq/Makefile
linux-2.6.0-test8-dbs/drivers/cpufreq/Makefile
--- linux-2.6.0-test8/drivers/cpufreq/Makefile	2003-10-17
14:43:38.000000000 -0700
+++ linux-2.6.0-test8-dbs/drivers/cpufreq/Makefile	2003-10-25
13:34:09.000000000 -0700
@@ -5,6 +5,7 @@ obj-$(CONFIG_CPU_FREQ)			+= cpufreq.o
 obj-$(CONFIG_CPU_FREQ_GOV_PERFORMANCE)	+= cpufreq_performance.o
 obj-$(CONFIG_CPU_FREQ_GOV_POWERSAVE)	+= cpufreq_powersave.o
 obj-$(CONFIG_CPU_FREQ_GOV_USERSPACE)	+= cpufreq_userspace.o
+obj-$(CONFIG_CPU_FREQ_GOV_ONDEMAND)	+= cpufreq_ondemand.o
 
 # CPUfreq cross-arch helpers
 obj-$(CONFIG_CPU_FREQ_TABLE)		+= freq_table.o

Attachment: ondemand2.patch
Description: ondemand2.patch