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Message-ID: <20081003165533.249261b1@infradead.org>
Date: Fri, 3 Oct 2008 16:55:33 -0700
From: Arjan van de Ven <arjan@...radead.org>
To: Steven Rostedt <rostedt@...dmis.org>, mingo@...e.hu
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] ftrace: Add a C-state tracer to help power optimization
From: Arjan van de Ven <arjan@...ux.intel.com>
Date: Fri, 3 Oct 2008 10:18:21 -0700
Subject: [PATCH] ftrace: Add a C-state tracer to help power optimization
This patch adds a C-state ftrace plugin that will generate
detailed statistics about the C-states that are being used,
so that we can look at detailed decisions that the C-state
code is making, rather than the too high level "average"
that we have today.
Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
arch/x86/kernel/process.c | 9 +++
include/linux/ftrace.h | 13 +++++
kernel/trace/Kconfig | 11 ++++
kernel/trace/Makefile | 1 +
kernel/trace/trace.h | 5 ++
kernel/trace/trace_cstate.c | 123 +++++++++++++++++++++++++++++++++++++++++++
6 files changed, 162 insertions(+), 0 deletions(-)
create mode 100644 kernel/trace/trace_cstate.c
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 3468131..68c7234 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 +101,8 @@ static inline int hlt_use_halt(void)
void default_idle(void)
{
if (hlt_use_halt()) {
+ struct cstate_trace it;
+ it.stamp = ktime_get();
current_thread_info()->status &= ~TS_POLLING;
/*
* TS_POLLING-cleared state must be visible before we
@@ -112,6 +115,8 @@ void default_idle(void)
else
local_irq_enable();
current_thread_info()->status |= TS_POLLING;
+ it.end = ktime_get();
+ trace_cstate(&it, 1);
} else {
local_irq_enable();
/* loop is done by the caller */
@@ -154,12 +159,16 @@ EXPORT_SYMBOL_GPL(cpu_idle_wait);
*/
void mwait_idle_with_hints(unsigned long ax, unsigned long cx)
{
+ struct cstate_trace it;
+ it.stamp = ktime_get();
if (!need_resched()) {
__monitor((void *)¤t_thread_info()->flags, 0, 0);
smp_mb();
if (!need_resched())
__mwait(ax, cx);
}
+ it.end = ktime_get();
+ trace_cstate(&it, (ax>>4)+1);
}
/* Default MONITOR/MWAIT with no hints, used for default C1 state */
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 91954eb..e6b4da6 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -226,6 +226,19 @@ static inline void trace_boot(struct boot_trace *it) { }
static inline void start_boot_trace(void) { }
#endif
+struct cstate_trace {
+ ktime_t stamp;
+ ktime_t end;
+ int state;
+ int CPU;
+};
+
+#ifdef CONFIG_CSTATE_TRACER
+extern void trace_cstate(struct cstate_trace *it, int state);
+#else
+static inline void trace_cstate(struct cstate_trace *it, int state) { }
+#endif
+
#endif /* _LINUX_FTRACE_H */
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 396aea1..fa2347a 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -134,6 +134,17 @@ config BOOT_TRACER
be enabled if this tracer is selected since only one tracer
should touch the tracing buffer at a time.
+config CSTATE_TRACER
+ bool "Trace C-state behavior"
+ depends on HAVE_FTRACE
+ depends on DEBUG_KERNEL
+ depends on X86
+ select TRACING
+ help
+ This tracer helps developers to analyize and optimize the kernels
+ power management decisions, specifically the C-state behavior.
+
+
config STACK_TRACER
bool "Trace max stack"
depends on HAVE_FTRACE
diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
index a85dfba..2b85724 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_CSTATE_TRACER) += trace_cstate.o
libftrace-y := ftrace.o
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index a921ba5..1ef1ded 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -117,6 +117,11 @@ struct trace_boot {
struct boot_trace initcall;
};
+struct trace_cstate {
+ struct trace_entry ent;
+ struct cstate_trace state_data;
+};
+
/*
* trace_flag_type is an enumeration that holds different
* states when a trace occurs. These are:
diff --git a/kernel/trace/trace_cstate.c b/kernel/trace/trace_cstate.c
new file mode 100644
index 0000000..fcd4e6e
--- /dev/null
+++ b/kernel/trace/trace_cstate.c
@@ -0,0 +1,123 @@
+/*
+ * ring buffer based C-state tracer
+ *
+ * Arjan van de Ven <arjan@...ux.intel.com>
+ * Copyright (C) 2009 Intel Corporation
+ *
+ * Much is borrowed from trace_boot.c which is
+ * Copyright (C) 2008 Frederic Weisbecker <fweisbec@...il.com>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <linux/ftrace.h>
+#include <linux/kallsyms.h>
+
+#include "trace.h"
+
+static struct trace_array *cstate_trace;
+static int trace_cstate_enabled;
+
+
+/* Should be started after do_pre_smp_initcalls() in init/main.c */
+static void start_cstate_trace(void)
+{
+ trace_cstate_enabled = 1;
+}
+
+void stop_cstate_trace(struct trace_array *tr)
+{
+ trace_cstate_enabled = 0;
+}
+
+static void cstate_trace_init(struct trace_array *tr)
+{
+ int cpu;
+ cstate_trace = tr;
+
+ trace_cstate_enabled = 1;
+
+ for_each_cpu_mask(cpu, cpu_possible_map)
+ tracing_reset(tr, cpu);
+}
+
+static void cstate_trace_ctrl_update(struct trace_array *tr)
+{
+ if (tr->ctrl)
+ start_cstate_trace();
+ else
+ stop_cstate_trace(tr);
+}
+
+static enum print_line_t cstate_print_line(struct trace_iterator *iter)
+{
+ int ret;
+ struct trace_entry *entry = iter->ent;
+ struct trace_cstate *field = (struct trace_cstate *)entry;
+ struct cstate_trace *it = &field->state_data;
+ struct trace_seq *s = &iter->seq;
+ struct timespec stamp = ktime_to_timespec(it->stamp);
+ struct timespec duration = ktime_to_timespec(
+ ktime_sub(it->end, it->stamp));
+
+ if (entry->type == TRACE_BOOT) {
+ ret = trace_seq_printf(s, "[%5ld.%09ld] Going to C%i on cpu %i for %ld.%09ld\n",
+ stamp.tv_sec,
+ stamp.tv_nsec,
+ it->state, it->CPU,
+ duration.tv_sec,
+ duration.tv_nsec);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+ return TRACE_TYPE_HANDLED;
+ }
+ return TRACE_TYPE_UNHANDLED;
+}
+
+struct tracer cstate_tracer __read_mostly =
+{
+ .name = "cstate",
+ .init = cstate_trace_init,
+ .reset = stop_cstate_trace,
+ .ctrl_update = cstate_trace_ctrl_update,
+ .print_line = cstate_print_line,
+};
+
+static int init_cstate_trace(void)
+{
+ return register_tracer(&cstate_tracer);
+}
+device_initcall(init_cstate_trace);
+
+void trace_cstate(struct cstate_trace *it, int level)
+{
+ struct ring_buffer_event *event;
+ struct trace_cstate *entry;
+ struct trace_array_cpu *data;
+ unsigned long irq_flags;
+ struct trace_array *tr = cstate_trace;
+
+ if (!trace_cstate_enabled)
+ return;
+
+ it->state = level;
+ preempt_disable();
+ it->CPU = smp_processor_id();
+ 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);
+ entry->ent.type = TRACE_BOOT;
+ entry->state_data = *it;
+ ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+
+ trace_wake_up();
+
+ out:
+ preempt_enable();
+}
--
1.5.5.1
--
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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