Xen devel - Oct 2007 - [PATCH][retry 2][cpufreq] Xen support for the ondemand governor in Linux dom0

Modify the cpufreq ondemand governor so that it can get idle and
total nsecs from the Xen hypervisor.  Xen uses nsecs to measure
idle time, while Linux uses ticks.  Other than accounting for 
that difference, use the same algorithm to calculate idle time
as Linux does.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>

diff -r 26962454b508 drivers/cpufreq/cpufreq_ondemand.c
--- a/drivers/cpufreq/cpufreq_ondemand.c	Wed Oct 24 17:17:09 2007 +0100
+++ b/drivers/cpufreq/cpufreq_ondemand.c	Mon Oct 29 12:39:23 2007 -0500
@@ -96,6 +96,7 @@ static inline cputime64_t get_cpu_idle_t
 	return retval;
 }
 
+
 /************************** sysfs interface ************************/
 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 {
@@ -221,18 +222,14 @@ static struct attribute_group dbs_attr_g
 };
 
 /************************** sysfs end ************************/
-
-static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
-{
-	unsigned int idle_ticks, total_ticks;
-	unsigned int load;
+#ifndef CONFIG_XEN
+static int dbs_calc_load(struct cpu_dbs_info_s *this_dbs_info)
+{
+	struct cpufreq_policy *policy;
 	cputime64_t cur_jiffies;
-
-	struct cpufreq_policy *policy;
+	cputime64_t total_ticks, idle_ticks;
 	unsigned int j;
-
-	if (!this_dbs_info->enable)
-		return;
+	int load;
 
 	policy = this_dbs_info->cur_policy;
 	cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
@@ -240,7 +237,7 @@ static void dbs_check_cpu(struct cpu_dbs
 			this_dbs_info->prev_cpu_wall);
 	this_dbs_info->prev_cpu_wall = cur_jiffies;
 	if (!total_ticks)
-		return;
+		return 200;
 	/*
 	 * Every sampling_rate, we check, if current idle time is less
 	 * than 20% (default), then we try to increase frequency
@@ -270,6 +267,70 @@ static void dbs_check_cpu(struct cpu_dbs
 			idle_ticks = tmp_idle_ticks;
 	}
 	load = (100 * (total_ticks - idle_ticks)) / total_ticks;
+	return load;
+}
+#else
+
+#include <xen/interface/platform.h>
+static int dbs_calc_load(struct cpu_dbs_info_s *this_dbs_info)
+{
+	int load = 0;
+	struct xen_platform_op op;
+	uint64_t idletime[NR_CPUS];
+	struct cpufreq_policy *policy;
+	unsigned int j;
+	cpumask_t cpumap;
+
+        op.cmd = XENPF_getidletime;
+	set_xen_guest_handle(op.u.getidletime.cpumap_bitmap, (uint8_t *)
cpus_addr(cpumap));
+        op.u.getidletime.cpumap_nr_cpus = NR_CPUS;// num_online_cpus();
+        set_xen_guest_handle(op.u.getidletime.idletime, idletime);
+        if (HYPERVISOR_platform_op(&op))
+		return 200;
+
+	policy = this_dbs_info->cur_policy;
+	cpumap = policy->cpus;
+	for_each_cpu_mask(j, cpumap) {
+		cputime64_t total_idle_nsecs, tmp_idle_nsecs;
+		cputime64_t total_wall_nsecs, tmp_wall_nsecs;
+		struct cpu_dbs_info_s *j_dbs_info;
+		unsigned long tmp_load;
+
+		j_dbs_info = &per_cpu(cpu_dbs_info, j);
+		total_idle_nsecs = idletime[j];
+		tmp_idle_nsecs = cputime64_sub(total_idle_nsecs,
+				j_dbs_info->prev_cpu_idle);
+		total_wall_nsecs = op.u.getidletime.now;
+		tmp_wall_nsecs = cputime64_sub(total_wall_nsecs,
+				j_dbs_info->prev_cpu_wall);
+
+		if (tmp_wall_nsecs == 0)
+			return 200;
+
+		j_dbs_info->prev_cpu_wall = total_wall_nsecs;
+		j_dbs_info->prev_cpu_idle = total_idle_nsecs;
+
+		tmp_load = (100 * (tmp_wall_nsecs - tmp_idle_nsecs)) /
+				tmp_wall_nsecs;
+		load = max(load, min(100, (int) tmp_load));
+	}
+	return load;
+}
+#endif
+
+static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
+{
+	int load;
+
+	struct cpufreq_policy *policy;
+
+	if (!this_dbs_info->enable)
+		return;
+
+	policy = this_dbs_info->cur_policy;
+	load = dbs_calc_load(this_dbs_info);
+	if (load > 100) 
+		return;
 
 	/* Check for frequency increase */
 	if (load > dbs_tuners_ins.up_threshold) {



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