[PATCH] ftrace: Add a C/P state tracer to help power optimization
From: Arjan van de Ven
Date: Fri Oct 03 2008 - 13:18:21 EST
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
Impact: New code
Impact: Minor additions to existing code
Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
---
arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c | 4 +
arch/x86/kernel/process.c | 16 +++
include/linux/ftrace.h | 29 +++++
kernel/trace/Kconfig | 11 ++
kernel/trace/Makefile | 1 +
kernel/trace/trace.h | 7 +
kernel/trace/trace_power.c | 184 ++++++++++++++++++++++++++++
7 files changed, 252 insertions(+), 0 deletions(-)
create mode 100644 kernel/trace/trace_power.c
diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index 8e48c5d..88ea02d 100644
--- a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
+++ b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
@@ -33,6 +33,7 @@
#include <linux/cpufreq.h>
#include <linux/compiler.h>
#include <linux/dmi.h>
+#include <linux/ftrace.h>
#include <linux/acpi.h>
#include <acpi/processor.h>
@@ -391,6 +392,7 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
unsigned int next_perf_state = 0; /* Index into perf table */
unsigned int i;
int result = 0;
+ struct power_trace it;
dprintk("acpi_cpufreq_target %d (%d)\n", target_freq, policy->cpu);
@@ -427,6 +429,8 @@ static int acpi_cpufreq_target(struct cpufreq_policy *policy,
}
}
+ trace_power_mark(&it, POWER_PSTATE, next_perf_state);
+
switch (data->cpu_feature) {
case SYSTEM_INTEL_MSR_CAPABLE:
cmd.type = SYSTEM_INTEL_MSR_CAPABLE;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c622772..c27af49 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -7,6 +7,7 @@
#include <linux/module.h>
#include <linux/pm.h>
#include <linux/clockchips.h>
+#include <linux/ftrace.h>
#include <asm/system.h>
unsigned long idle_halt;
@@ -100,6 +101,9 @@ static inline int hlt_use_halt(void)
void default_idle(void)
{
if (hlt_use_halt()) {
+ struct power_trace it;
+
+ trace_power_start(&it, POWER_CSTATE, 1);
current_thread_info()->status &= ~TS_POLLING;
/*
* TS_POLLING-cleared state must be visible before we
@@ -112,6 +116,7 @@ void default_idle(void)
else
local_irq_enable();
current_thread_info()->status |= TS_POLLING;
+ trace_power_end(&it);
} else {
local_irq_enable();
/* loop is done by the caller */
@@ -154,24 +159,31 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
*/
void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
{
+ struct power_trace it;
+
+ trace_power_start(&it, POWER_CSTATE, (ax>>4)+1);
if (!need_resched()) {
__monitor((void *)¤t_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
__mwait(ax, cx);
}
+ trace_power_end(&it);
}
/* Default MONITOR/MWAIT with no hints, used for default C1 state */
static void mwait_idle(void)
{
+ struct power_trace it;
if (!need_resched()) {
+ trace_power_start(&it, POWER_CSTATE, 1);
__monitor((void *)¤t_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
__sti_mwait(0, 0);
else
local_irq_enable();
+ trace_power_end(&it);
} else
local_irq_enable();
}
@@ -183,9 +195,13 @@ static void mwait_idle(void)
*/
static void poll_idle(void)
{
+ struct power_trace it;
+
+ trace_power_start(&it, POWER_CSTATE, 0);
local_irq_enable();
while (!need_resched())
cpu_relax();
+ trace_power_end(&it);
}
/*
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 703eb53..573095b 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -248,6 +248,35 @@ static inline void start_boot_trace(void) { }
static inline void stop_boot_trace(void) { }
#endif
+enum {
+ POWER_NONE = 0,
+ POWER_CSTATE = 1,
+ POWER_PSTATE = 2,
+};
+
+struct power_trace {
+#ifdef CONFIG_POWER_TRACER
+ ktime_t stamp;
+ ktime_t end;
+ int type;
+ int state;
+#endif
+};
+
+#ifdef CONFIG_POWER_TRACER
+extern void trace_power_start(struct power_trace *it, unsigned int type,
+ unsigned int state);
+extern void trace_power_mark(struct power_trace *it, unsigned int type,
+ unsigned int state);
+extern void trace_power_end(struct power_trace *it);
+#else
+static inline void trace_power_start(struct power_trace *it, unsigned int type,
+ unsigned int state) { }
+static inline void trace_power_mark(struct power_trace *it, unsigned int type,
+ unsigned int state) { }
+static inline void trace_power_end(struct power_trace *it) { }
+#endif
+
#endif /* _LINUX_FTRACE_H */
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 33dbefd..f5f2363 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -138,6 +138,17 @@ config BOOT_TRACER
selected, because the self-tests are an initcall as well and that
would invalidate the boot trace. )
+config POWER_TRACER
+ bool "Trace power consumption behavior"
+ depends on DEBUG_KERNEL
+ depends on X86
+ select TRACING
+ help
+ This tracer helps developers to analyze and optimize the kernels
+ power management decisions, specifically the C-state and P-state
+ behavior.
+
+
config STACK_TRACER
bool "Trace max stack"
depends on HAVE_FUNCTION_TRACER
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index c8228b1..917b42e 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -24,5 +24,6 @@ obj-$(CONFIG_NOP_TRACER) += trace_nop.o
obj-$(CONFIG_STACK_TRACER) += trace_stack.o
obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
obj-$(CONFIG_BOOT_TRACER) += trace_boot.o
+obj-$(CONFIG_POWER_TRACER) += trace_power.o
libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 8465ad0..77cc01c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -22,6 +22,7 @@ enum trace_type {
TRACE_MMIO_RW,
TRACE_MMIO_MAP,
TRACE_BOOT,
+ TRACE_POWER,
__TRACE_LAST_TYPE
};
@@ -117,6 +118,11 @@ struct trace_boot {
struct boot_trace initcall;
};
+struct trace_power {
+ struct trace_entry ent;
+ struct power_trace state_data;
+};
+
/*
* trace_flag_type is an enumeration that holds different
* states when a trace occurs. These are:
@@ -219,6 +225,7 @@ extern void __ftrace_bad_type(void);
IF_ASSIGN(var, ent, struct trace_mmiotrace_map, \
TRACE_MMIO_MAP); \
IF_ASSIGN(var, ent, struct trace_boot, TRACE_BOOT); \
+ IF_ASSIGN(var, ent, struct trace_power, TRACE_POWER); \
__ftrace_bad_type(); \
} while (0)
diff --git a/kernel/trace/trace_power.c b/kernel/trace/trace_power.c
new file mode 100644
index 0000000..db51f3f
--- /dev/null
+++ b/kernel/trace/trace_power.c
@@ -0,0 +1,184 @@
+/*
+ * ring buffer based C-state tracer
+ *
+ * Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
+ * Copyright (C) 2008 Intel Corporation
+ *
+ * Much is borrowed from trace_boot.c which is
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@xxxxxxxxx>
+ *
+ */
+
+#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(void)
+{
+ trace_power_enabled = 1;
+}
+
+static void stop_power_trace(struct trace_array *tr)
+{
+ trace_power_enabled = 0;
+}
+
+static void 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);
+}
+
+static void power_trace_ctrl_update(struct trace_array *tr)
+{
+ if (tr->ctrl)
+ start_power_trace();
+ else
+ stop_power_trace(tr);
+}
+
+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,
+ .reset = stop_power_trace,
+ .ctrl_update = power_trace_ctrl_update,
+ .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);
--
1.6.0.3
--
Arjan van de Ven Intel Open Source Technology Centre
For development, discussion and tips for power savings,
visit http://www.lesswatts.org
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