tracing: add "power-tracer": C/P state tracer to help power optimization

Impact: new "power-tracer" ftrace plugin

This patch adds a C/P-state ftrace plugin that will generate
detailed statistics about the C/P-states that are being used,
so that we can look at detailed decisions that the C/P-state
code is making, rather than the too high level "average"
that we have today.

An example way of using this is:

 mount -t debugfs none /sys/kernel/debug
 echo cstate > /sys/kernel/debug/tracing/current_tracer
 echo 1 > /sys/kernel/debug/tracing/tracing_enabled
 sleep 1
 echo 0 > /sys/kernel/debug/tracing/tracing_enabled
 cat /sys/kernel/debug/tracing/trace | perl scripts/trace/cstate.pl > out.svg

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 179 insertions, 0 deletions

diff --git a/kernel/trace/trace_power.c b/kernel/trace/trace_power.c
new file mode 100644
index 000000000000..a7172a352f62
--- /dev/null
+++ b/kernel/trace/trace_power.c
@@ -0,0 +1,179 @@
+/*
+ * ring buffer based C-state tracer
+ *
+ * Arjan van de Ven <arjan@linux.intel.com>
+ * Copyright (C) 2008 Intel Corporation
+ *
+ * Much is borrowed from trace_boot.c which is
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <linux/ftrace.h>
+#include <linux/kallsyms.h>
+#include <linux/module.h>
+
+#include "trace.h"
+
+static struct trace_array *power_trace;
+static int __read_mostly trace_power_enabled;
+
+
+static void start_power_trace(struct trace_array *tr)
+{
+	trace_power_enabled = 1;
+}
+
+static void stop_power_trace(struct trace_array *tr)
+{
+	trace_power_enabled = 0;
+}
+
+
+static int power_trace_init(struct trace_array *tr)
+{
+	int cpu;
+	power_trace = tr;
+
+	trace_power_enabled = 1;
+
+	for_each_cpu_mask(cpu, cpu_possible_map)
+		tracing_reset(tr, cpu);
+	return 0;
+}
+
+static enum print_line_t power_print_line(struct trace_iterator *iter)
+{
+	int ret = 0;
+	struct trace_entry *entry = iter->ent;
+	struct trace_power *field ;
+	struct power_trace *it;
+	struct trace_seq *s = &iter->seq;
+	struct timespec stamp;
+	struct timespec duration;
+
+	trace_assign_type(field, entry);
+	it = &field->state_data;
+	stamp = ktime_to_timespec(it->stamp);
+	duration = ktime_to_timespec(ktime_sub(it->end, it->stamp));
+
+	if (entry->type == TRACE_POWER) {
+		if (it->type == POWER_CSTATE)
+			ret = trace_seq_printf(s, "[%5ld.%09ld] CSTATE: Going to C%i on cpu %i for %ld.%09ld\n",
+					  stamp.tv_sec,
+					  stamp.tv_nsec,
+					  it->state, iter->cpu,
+					  duration.tv_sec,
+					  duration.tv_nsec);
+		if (it->type == POWER_PSTATE)
+			ret = trace_seq_printf(s, "[%5ld.%09ld] PSTATE: Going to P%i on cpu %i\n",
+					  stamp.tv_sec,
+					  stamp.tv_nsec,
+					  it->state, iter->cpu);
+		if (!ret)
+			return TRACE_TYPE_PARTIAL_LINE;
+		return TRACE_TYPE_HANDLED;
+	}
+	return TRACE_TYPE_UNHANDLED;
+}
+
+static struct tracer power_tracer __read_mostly =
+{
+	.name		= "power",
+	.init		= power_trace_init,
+	.start		= start_power_trace,
+	.stop		= stop_power_trace,
+	.reset		= stop_power_trace,
+	.print_line	= power_print_line,
+};
+
+static int init_power_trace(void)
+{
+	return register_tracer(&power_tracer);
+}
+device_initcall(init_power_trace);
+
+void trace_power_start(struct power_trace *it, unsigned int type,
+			 unsigned int level)
+{
+	if (!trace_power_enabled)
+		return;
+
+	memset(it, 0, sizeof(struct power_trace));
+	it->state = level;
+	it->type = type;
+	it->stamp = ktime_get();
+}
+EXPORT_SYMBOL_GPL(trace_power_start);
+
+
+void trace_power_end(struct power_trace *it)
+{
+	struct ring_buffer_event *event;
+	struct trace_power *entry;
+	struct trace_array_cpu *data;
+	unsigned long irq_flags;
+	struct trace_array *tr = power_trace;
+
+	if (!trace_power_enabled)
+		return;
+
+	preempt_disable();
+	it->end = ktime_get();
+	data = tr->data[smp_processor_id()];
+
+	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
+					 &irq_flags);
+	if (!event)
+		goto out;
+	entry	= ring_buffer_event_data(event);
+	tracing_generic_entry_update(&entry->ent, 0, 0);
+	entry->ent.type = TRACE_POWER;
+	entry->state_data = *it;
+	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+
+	trace_wake_up();
+
+ out:
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(trace_power_end);
+
+void trace_power_mark(struct power_trace *it, unsigned int type,
+			 unsigned int level)
+{
+	struct ring_buffer_event *event;
+	struct trace_power *entry;
+	struct trace_array_cpu *data;
+	unsigned long irq_flags;
+	struct trace_array *tr = power_trace;
+
+	if (!trace_power_enabled)
+		return;
+
+	memset(it, 0, sizeof(struct power_trace));
+	it->state = level;
+	it->type = type;
+	it->stamp = ktime_get();
+	preempt_disable();
+	it->end = it->stamp;
+	data = tr->data[smp_processor_id()];
+
+	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
+					 &irq_flags);
+	if (!event)
+		goto out;
+	entry	= ring_buffer_event_data(event);
+	tracing_generic_entry_update(&entry->ent, 0, 0);
+	entry->ent.type = TRACE_POWER;
+	entry->state_data = *it;
+	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+
+	trace_wake_up();
+
+ out:
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(trace_power_mark);