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>

8 files changed, 355 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/x86/kernel/cpu/cpufreq/acpi-cpufreq.c
index 8e48c5d4467d..88ea02dcb622 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 c622772744d8..c27af49a4ede 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 *)&current_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 *)&current_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 7854d87b97b2..0df288666201 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -311,6 +311,35 @@ ftrace_init_module(struct module *mod,
                    unsigned long *start, unsigned long *end) { }
 #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
+
 
 /*
  * Structure that defines a return function trace.
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 620feadff67a..d151aab48ed6 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -217,6 +217,17 @@ config BRANCH_TRACER
 
           Say N if unsure.
 
+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 cef4bcb4e822..acaa06553eca 100644
--- a/kernel/trace/Makefile
+++ b/kernel/trace/Makefile
@@ -32,5 +32,6 @@ obj-$(CONFIG_BOOT_TRACER) += trace_boot.o
 obj-$(CONFIG_FUNCTION_RET_TRACER) += trace_functions_return.o
 obj-$(CONFIG_TRACE_BRANCH_PROFILING) += trace_branch.o
 obj-$(CONFIG_BTS_TRACER) += trace_bts.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 3abd645e8af2..4c453778a6ab 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -28,6 +28,7 @@ enum trace_type {
         TRACE_FN_RET,
         TRACE_USER_STACK,
         TRACE_BTS,
+        TRACE_POWER,
 
         __TRACE_LAST_TYPE
 };
@@ -160,6 +161,11 @@ struct bts_entry {
         unsigned long           to;
 };
 
+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:
@@ -266,6 +272,7 @@ extern void __ftrace_bad_type(void);
                 IF_ASSIGN(var, ent, struct trace_branch, TRACE_BRANCH); \
                 IF_ASSIGN(var, ent, struct ftrace_ret_entry, TRACE_FN_RET);\
                 IF_ASSIGN(var, ent, struct bts_entry, TRACE_BTS);\
+                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 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);
diff --git a/scripts/trace/power.pl b/scripts/trace/power.pl
new file mode 100644
index 000000000000..4f729b3501e0
--- /dev/null
+++ b/scripts/trace/power.pl
@@ -0,0 +1,108 @@
+#!/usr/bin/perl
+
+# Copyright 2008, Intel Corporation
+#
+# This file is part of the Linux kernel
+#
+# This program file is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by the
+# Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+# for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program in a file named COPYING; if not, write to the
+# Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor,
+# Boston, MA 02110-1301 USA
+#
+# Authors:
+#       Arjan van de Ven <arjan@linux.intel.com>
+
+
+#
+# This script turns a cstate ftrace output into a SVG graphic that shows
+# historic C-state information
+#
+#
+#       cat /sys/kernel/debug/tracing/trace | perl power.pl > out.svg
+#
+
+my @styles;
+my $base = 0;
+
+my @pstate_last;
+my @pstate_level;
+
+$styles[0] = "fill:rgb(0,0,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[1] = "fill:rgb(0,255,0);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[2] = "fill:rgb(255,0,20);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[3] = "fill:rgb(255,255,20);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[4] = "fill:rgb(255,0,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[5] = "fill:rgb(0,255,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[6] = "fill:rgb(0,128,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[7] = "fill:rgb(0,255,128);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[8] = "fill:rgb(0,25,20);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+
+
+print "<?xml version=\"1.0\" standalone=\"no\"?> \n";
+print "<svg width=\"10000\" height=\"100%\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\">\n";
+
+my $scale = 30000.0;
+while (<>) {
+        my $line = $_;
+        if ($line =~ /([0-9\.]+)\] CSTATE: Going to C([0-9]) on cpu ([0-9]+) for ([0-9\.]+)/) {
+                if ($base == 0) {
+                        $base = $1;
+                }
+                my $time = $1 - $base;
+                $time = $time * $scale;
+                my $C = $2;
+                my $cpu = $3;
+                my $y = 400 * $cpu;
+                my $duration = $4 * $scale;
+                my $msec = int($4 * 100000)/100.0;
+                my $height = $C * 20;
+                $style = $styles[$C];
+
+                $y = $y + 140 - $height;
+
+                $x2 = $time + 4;
+                $y2 = $y + 4;
+
+
+                print "<rect x=\"$time\" width=\"$duration\" y=\"$y\" height=\"$height\" style=\"$style\"/>\n";
+                print "<text transform=\"translate($x2,$y2) rotate(90)\">C$C $msec</text>\n";
+        }
+        if ($line =~ /([0-9\.]+)\] PSTATE: Going to P([0-9]) on cpu ([0-9]+)/) {
+                my $time = $1 - $base;
+                my $state = $2;
+                my $cpu = $3;
+
+                if (defined($pstate_last[$cpu])) {
+                        my $from = $pstate_last[$cpu];
+                        my $oldstate = $pstate_state[$cpu];
+                        my $duration = ($time-$from) * $scale;
+
+                        $from = $from * $scale;
+                        my $to = $from + $duration;
+                        my $height = 140 - ($oldstate * (140/8));
+
+                        my $y = 400 * $cpu + 200 + $height;
+                        my $y2 = $y+4;
+                        my $style = $styles[8];
+
+                        print "<rect x=\"$from\" y=\"$y\" width=\"$duration\" height=\"5\" style=\"$style\"/>\n";
+                        print "<text transform=\"translate($from,$y2)\">P$oldstate (cpu $cpu)</text>\n";
+                };
+
+                $pstate_last[$cpu] = $time;
+                $pstate_state[$cpu] = $state;
+        }
+}
+
+
+print "</svg>\n";