trace_branch.c

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/*
 * unlikely profiler
 *
 * Copyright (C) 2008 Steven Rostedt <[email protected]>
 */
#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_stat.h"
#include "trace_output.h"

#ifdef CONFIG_BRANCH_TRACER

static struct tracer branch_trace;
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 ftrace_event_call *call = &event_branch;
    struct trace_array *tr = branch_tracer;
    struct ring_buffer_event *event;
    struct trace_branch *entry;
    struct ring_buffer *buffer;
    unsigned long 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;

    pc = preempt_count();
    buffer = tr->buffer;
    event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
                      sizeof(*entry), flags, pc);
    if (!event)
        goto out;

    entry   = ring_buffer_event_data(event);

    /* 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;

    if (!filter_check_discard(call, entry, buffer, event))
        ring_buffer_unlock_commit(buffer, event);

 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)
{
    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 0;
}

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)
{
    start_branch_trace(tr);
    return 0;
}

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

static enum print_line_t trace_branch_print(struct trace_iterator *iter,
                        int flags, struct trace_event *event)
{
    struct trace_branch *field;

    trace_assign_type(field, iter->ent);

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

    return TRACE_TYPE_HANDLED;
}

static void branch_print_header(struct seq_file *s)
{
    seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
        "  FUNC:FILE:LINE\n");
    seq_puts(s, "#              | |       |          |         |   "
        "    |\n");
}

static struct trace_event_functions trace_branch_funcs = {
    .trace      = trace_branch_print,
};

static struct trace_event trace_branch_event = {
    .type       = TRACE_BRANCH,
    .funcs      = &trace_branch_funcs,
};

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

__init static int init_branch_tracer(void)
{
    int ret;

    ret = register_ftrace_event(&trace_branch_event);
    if (!ret) {
        printk(KERN_WARNING "Warning: could not register "
                    "branch events\n");
        return 1;
    }
    return register_tracer(&branch_trace);
}
device_initcall(init_branch_tracer);

#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(struct tracer_stat *trace)
{
    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;

    if (a->incorrect < b->incorrect)
        return -1;
    if (a->incorrect > b->incorrect)
        return 1;

    /*
     * Since the above shows worse (incorrect) cases
     * first, we continue that by showing best (correct)
     * cases last.
     */
    if (a->correct > b->correct)
        return -1;
    if (a->correct < b->correct)
        return 1;

    return 0;
}

static struct tracer_stat annotated_branch_stats = {
    .name = "branch_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
};

__init static int init_annotated_branch_stats(void)
{
    int ret;

    ret = register_stat_tracer(&annotated_branch_stats);
    if (!ret) {
        printk(KERN_WARNING "Warning: could not register "
                    "annotated branches stats\n");
        return 1;
    }
    return 0;
}
fs_initcall(init_annotated_branch_stats);

#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(struct tracer_stat *trace)
{
    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 all_branch_stats = {
    .name = "branch_all",
    .stat_start = all_branch_stat_start,
    .stat_next = all_branch_stat_next,
    .stat_headers = all_branch_stat_headers,
    .stat_show = branch_stat_show
};

__init static int all_annotated_branch_stats(void)
{
    int ret;

    ret = register_stat_tracer(&all_branch_stats);
    if (!ret) {
        printk(KERN_WARNING "Warning: could not register "
                    "all branches stats\n");
        return 1;
    }
    return 0;
}
fs_initcall(all_annotated_branch_stats);
#endif /* CONFIG_PROFILE_ALL_BRANCHES */