linux/kernel/trace/trace_branch.c

/*
 * unlikely profiler
 *
 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
 */
#include <linux/kallsyms.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/irqflags.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/ftrace.h>
#include <linux/hash.h>
#include <linux/fs.h>
#include <asm/local.h>

#include "trace.h"
#include "trace_output.h"

static struct tracer branch_trace;

#ifdef CONFIG_BRANCH_TRACER

static int branch_tracing_enabled __read_mostly;
static DEFINE_MUTEX(branch_tracing_mutex);

static struct trace_array *branch_tracer;

static void
probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
	struct trace_array *tr = branch_tracer;
	struct ring_buffer_event *event;
	struct trace_branch *entry;
	unsigned long flags, irq_flags;
	int cpu, pc;
	const char *p;

	/*
	 * I would love to save just the ftrace_likely_data pointer, but
	 * this code can also be used by modules. Ugly things can happen
	 * if the module is unloaded, and then we go and read the
	 * pointer.  This is slower, but much safer.
	 */

	if (unlikely(!tr))
		return;

	local_irq_save(flags);
	cpu = raw_smp_processor_id();
	if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
		goto out;

	event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
					 &irq_flags);
	if (!event)
		goto out;

	pc = preempt_count();
	entry	= ring_buffer_event_data(event);
	tracing_generic_entry_update(&entry->ent, flags, pc);
	entry->ent.type		= TRACE_BRANCH;

	/* Strip off the path, only save the file */
	p = f->file + strlen(f->file);
	while (p >= f->file && *p != '/')
		p--;
	p++;

	strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
	strncpy(entry->file, p, TRACE_FILE_SIZE);
	entry->func[TRACE_FUNC_SIZE] = 0;
	entry->file[TRACE_FILE_SIZE] = 0;
	entry->line = f->line;
	entry->correct = val == expect;

	ring_buffer_unlock_commit(tr->buffer, event, irq_flags);

 out:
	atomic_dec(&tr->data[cpu]->disabled);
	local_irq_restore(flags);
}

static inline
void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
	if (!branch_tracing_enabled)
		return;

	probe_likely_condition(f, val, expect);
}

int enable_branch_tracing(struct trace_array *tr)
{
	int ret = 0;

	mutex_lock(&branch_tracing_mutex);
	branch_tracer = tr;
	/*
	 * Must be seen before enabling. The reader is a condition
	 * where we do not need a matching rmb()
	 */
	smp_wmb();
	branch_tracing_enabled++;
	mutex_unlock(&branch_tracing_mutex);

	return ret;
}

void disable_branch_tracing(void)
{
	mutex_lock(&branch_tracing_mutex);

	if (!branch_tracing_enabled)
		goto out_unlock;

	branch_tracing_enabled--;

 out_unlock:
	mutex_unlock(&branch_tracing_mutex);
}

static void start_branch_trace(struct trace_array *tr)
{
	enable_branch_tracing(tr);
}

static void stop_branch_trace(struct trace_array *tr)
{
	disable_branch_tracing();
}

static int branch_trace_init(struct trace_array *tr)
{
	int cpu;

	for_each_online_cpu(cpu)
		tracing_reset(tr, cpu);

	start_branch_trace(tr);
	return 0;
}

static void branch_trace_reset(struct trace_array *tr)
{
	stop_branch_trace(tr);
}

static int
trace_print_print(struct trace_seq *s, struct trace_entry *entry, int flags)
{
	struct print_entry *field;

	trace_assign_type(field, entry);

	if (seq_print_ip_sym(s, field->ip, flags))
		goto partial;

	if (trace_seq_printf(s, ": %s", field->buf))
		goto partial;

 partial:
	return TRACE_TYPE_PARTIAL_LINE;
}

static int
trace_branch_print(struct trace_seq *s, struct trace_entry *entry, int flags)
{
	struct trace_branch *field;

	trace_assign_type(field, entry);

	if (trace_seq_printf(s, "[%s] %s:%s:%d\n",
			     field->correct ? "  ok  " : " MISS ",
			     field->func,
			     field->file,
			     field->line))
		return TRACE_TYPE_PARTIAL_LINE;

	return 0;
}


static struct trace_event trace_branch_event = {
	.type	 	= TRACE_BRANCH,
	.trace		= trace_branch_print,
	.latency_trace	= trace_branch_print,
	.raw		= trace_nop_print,
	.hex		= trace_nop_print,
	.binary		= trace_nop_print,
};

#else
static inline
void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
{
}
#endif /* CONFIG_BRANCH_TRACER */

void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
{
	/*
	 * I would love to have a trace point here instead, but the
	 * trace point code is so inundated with unlikely and likely
	 * conditions that the recursive nightmare that exists is too
	 * much to try to get working. At least for now.
	 */
	trace_likely_condition(f, val, expect);

	/* FIXME: Make this atomic! */
	if (val == expect)
		f->correct++;
	else
		f->incorrect++;
}
EXPORT_SYMBOL(ftrace_likely_update);

extern unsigned long __start_annotated_branch_profile[];
extern unsigned long __stop_annotated_branch_profile[];

static int annotated_branch_stat_headers(struct seq_file *m)
{
	seq_printf(m, " correct incorrect  %% ");
	seq_printf(m, "       Function                "
			      "  File              Line\n"
			      " ------- ---------  - "
			      "       --------                "
			      "  ----              ----\n");
	return 0;
}

static inline long get_incorrect_percent(struct ftrace_branch_data *p)
{
	long percent;

	if (p->correct) {
		percent = p->incorrect * 100;
		percent /= p->correct + p->incorrect;
	} else
		percent = p->incorrect ? 100 : -1;

	return percent;
}

static int branch_stat_show(struct seq_file *m, void *v)
{
	struct ftrace_branch_data *p = v;
	const char *f;
	long percent;

	/* Only print the file, not the path */
	f = p->file + strlen(p->file);
	while (f >= p->file && *f != '/')
		f--;
	f++;

	/*
	 * The miss is overlayed on correct, and hit on incorrect.
	 */
	percent = get_incorrect_percent(p);

	seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
	if (percent < 0)
		seq_printf(m, "  X ");
	else
		seq_printf(m, "%3ld ", percent);
	seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
	return 0;
}

static void *annotated_branch_stat_start(void)
{
	return __start_annotated_branch_profile;
}

static void *
annotated_branch_stat_next(void *v, int idx)
{
	struct ftrace_branch_data *p = v;

	++p;

	if ((void *)p >= (void *)__stop_annotated_branch_profile)
		return NULL;

	return p;
}

static int annotated_branch_stat_cmp(void *p1, void *p2)
{
	struct ftrace_branch_data *a = p1;
	struct ftrace_branch_data *b = p2;

	long percent_a, percent_b;

	percent_a = get_incorrect_percent(a);
	percent_b = get_incorrect_percent(b);

	if (percent_a < percent_b)
		return -1;
	if (percent_a > percent_b)
		return 1;
	else
		return 0;
}

#ifdef CONFIG_PROFILE_ALL_BRANCHES

extern unsigned long __start_branch_profile[];
extern unsigned long __stop_branch_profile[];

static int all_branch_stat_headers(struct seq_file *m)
{
	seq_printf(m, "   miss      hit    %% ");
	seq_printf(m, "       Function                "
			      "  File              Line\n"
			      " ------- ---------  - "
			      "       --------                "
			      "  ----              ----\n");
	return 0;
}

static void *all_branch_stat_start(void)
{
	return __start_branch_profile;
}

static void *
all_branch_stat_next(void *v, int idx)
{
	struct ftrace_branch_data *p = v;

	++p;

	if ((void *)p >= (void *)__stop_branch_profile)
		return NULL;

	return p;
}

static struct tracer_stat branch_stats[] = {
	{.name = "annotated",
	.stat_start = annotated_branch_stat_start,
	.stat_next = annotated_branch_stat_next,
	.stat_cmp = annotated_branch_stat_cmp,
	.stat_headers = annotated_branch_stat_headers,
	.stat_show = branch_stat_show},

	{.name = "all",
	.stat_start = all_branch_stat_start,
	.stat_next = all_branch_stat_next,
	.stat_headers = all_branch_stat_headers,
	.stat_show = branch_stat_show},

	{ }
};
#else
static struct tracer_stat branch_stats[] = {
	{.name = "annotated",
	.stat_start = annotated_branch_stat_start,
	.stat_next = annotated_branch_stat_next,
	.stat_cmp = annotated_branch_stat_cmp,
	.stat_headers = annotated_branch_stat_headers,
	.stat_show = branch_stat_show},

	{ }
};
#endif /* CONFIG_PROFILE_ALL_BRANCHES */


static struct tracer branch_trace __read_mostly =
{
	.name		= "branch",
#ifdef CONFIG_BRANCH_TRACER
	.init		= branch_trace_init,
	.reset		= branch_trace_reset,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest	= trace_selftest_startup_branch,
#endif /* CONFIG_FTRACE_SELFTEST */
#endif
	.stats		= branch_stats
};

__init static int init_branch_trace(void)
{
#ifdef CONFIG_BRANCH_TRACER
	int ret;
	ret = register_ftrace_event(&trace_branch_event);
	if (!ret) {
		printk(KERN_WARNING "Warning: could not register branch events\n");
		return 1;
	}
#endif

	return register_tracer(&branch_trace);
}
device_initcall(init_branch_trace);