Root/kernel/trace/trace_branch.c

1/*
2 * unlikely profiler
3 *
4 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
5 */
6#include <linux/kallsyms.h>
7#include <linux/seq_file.h>
8#include <linux/spinlock.h>
9#include <linux/irqflags.h>
10#include <linux/debugfs.h>
11#include <linux/uaccess.h>
12#include <linux/module.h>
13#include <linux/ftrace.h>
14#include <linux/hash.h>
15#include <linux/fs.h>
16#include <asm/local.h>
17
18#include "trace.h"
19#include "trace_stat.h"
20#include "trace_output.h"
21
22#ifdef CONFIG_BRANCH_TRACER
23
24static struct tracer branch_trace;
25static int branch_tracing_enabled __read_mostly;
26static DEFINE_MUTEX(branch_tracing_mutex);
27
28static struct trace_array *branch_tracer;
29
30static void
31probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
32{
33    struct ftrace_event_call *call = &event_branch;
34    struct trace_array *tr = branch_tracer;
35    struct ring_buffer_event *event;
36    struct trace_branch *entry;
37    struct ring_buffer *buffer;
38    unsigned long flags;
39    int cpu, pc;
40    const char *p;
41
42    /*
43     * I would love to save just the ftrace_likely_data pointer, but
44     * this code can also be used by modules. Ugly things can happen
45     * if the module is unloaded, and then we go and read the
46     * pointer. This is slower, but much safer.
47     */
48
49    if (unlikely(!tr))
50        return;
51
52    local_irq_save(flags);
53    cpu = raw_smp_processor_id();
54    if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
55        goto out;
56
57    pc = preempt_count();
58    buffer = tr->buffer;
59    event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
60                      sizeof(*entry), flags, pc);
61    if (!event)
62        goto out;
63
64    entry = ring_buffer_event_data(event);
65
66    /* Strip off the path, only save the file */
67    p = f->file + strlen(f->file);
68    while (p >= f->file && *p != '/')
69        p--;
70    p++;
71
72    strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
73    strncpy(entry->file, p, TRACE_FILE_SIZE);
74    entry->func[TRACE_FUNC_SIZE] = 0;
75    entry->file[TRACE_FILE_SIZE] = 0;
76    entry->line = f->line;
77    entry->correct = val == expect;
78
79    if (!filter_check_discard(call, entry, buffer, event))
80        ring_buffer_unlock_commit(buffer, event);
81
82 out:
83    atomic_dec(&tr->data[cpu]->disabled);
84    local_irq_restore(flags);
85}
86
87static inline
88void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
89{
90    if (!branch_tracing_enabled)
91        return;
92
93    probe_likely_condition(f, val, expect);
94}
95
96int enable_branch_tracing(struct trace_array *tr)
97{
98    mutex_lock(&branch_tracing_mutex);
99    branch_tracer = tr;
100    /*
101     * Must be seen before enabling. The reader is a condition
102     * where we do not need a matching rmb()
103     */
104    smp_wmb();
105    branch_tracing_enabled++;
106    mutex_unlock(&branch_tracing_mutex);
107
108    return 0;
109}
110
111void disable_branch_tracing(void)
112{
113    mutex_lock(&branch_tracing_mutex);
114
115    if (!branch_tracing_enabled)
116        goto out_unlock;
117
118    branch_tracing_enabled--;
119
120 out_unlock:
121    mutex_unlock(&branch_tracing_mutex);
122}
123
124static void start_branch_trace(struct trace_array *tr)
125{
126    enable_branch_tracing(tr);
127}
128
129static void stop_branch_trace(struct trace_array *tr)
130{
131    disable_branch_tracing();
132}
133
134static int branch_trace_init(struct trace_array *tr)
135{
136    start_branch_trace(tr);
137    return 0;
138}
139
140static void branch_trace_reset(struct trace_array *tr)
141{
142    stop_branch_trace(tr);
143}
144
145static enum print_line_t trace_branch_print(struct trace_iterator *iter,
146                        int flags, struct trace_event *event)
147{
148    struct trace_branch *field;
149
150    trace_assign_type(field, iter->ent);
151
152    if (trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
153                 field->correct ? " ok " : " MISS ",
154                 field->func,
155                 field->file,
156                 field->line))
157        return TRACE_TYPE_PARTIAL_LINE;
158
159    return TRACE_TYPE_HANDLED;
160}
161
162static void branch_print_header(struct seq_file *s)
163{
164    seq_puts(s, "# TASK-PID CPU# TIMESTAMP CORRECT"
165        " FUNC:FILE:LINE\n");
166    seq_puts(s, "# | | | | | "
167        " |\n");
168}
169
170static struct trace_event_functions trace_branch_funcs = {
171    .trace = trace_branch_print,
172};
173
174static struct trace_event trace_branch_event = {
175    .type = TRACE_BRANCH,
176    .funcs = &trace_branch_funcs,
177};
178
179static struct tracer branch_trace __read_mostly =
180{
181    .name = "branch",
182    .init = branch_trace_init,
183    .reset = branch_trace_reset,
184#ifdef CONFIG_FTRACE_SELFTEST
185    .selftest = trace_selftest_startup_branch,
186#endif /* CONFIG_FTRACE_SELFTEST */
187    .print_header = branch_print_header,
188};
189
190__init static int init_branch_tracer(void)
191{
192    int ret;
193
194    ret = register_ftrace_event(&trace_branch_event);
195    if (!ret) {
196        printk(KERN_WARNING "Warning: could not register "
197                    "branch events\n");
198        return 1;
199    }
200    return register_tracer(&branch_trace);
201}
202device_initcall(init_branch_tracer);
203
204#else
205static inline
206void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
207{
208}
209#endif /* CONFIG_BRANCH_TRACER */
210
211void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
212{
213    /*
214     * I would love to have a trace point here instead, but the
215     * trace point code is so inundated with unlikely and likely
216     * conditions that the recursive nightmare that exists is too
217     * much to try to get working. At least for now.
218     */
219    trace_likely_condition(f, val, expect);
220
221    /* FIXME: Make this atomic! */
222    if (val == expect)
223        f->correct++;
224    else
225        f->incorrect++;
226}
227EXPORT_SYMBOL(ftrace_likely_update);
228
229extern unsigned long __start_annotated_branch_profile[];
230extern unsigned long __stop_annotated_branch_profile[];
231
232static int annotated_branch_stat_headers(struct seq_file *m)
233{
234    seq_printf(m, " correct incorrect %% ");
235    seq_printf(m, " Function "
236                  " File Line\n"
237                  " ------- --------- - "
238                  " -------- "
239                  " ---- ----\n");
240    return 0;
241}
242
243static inline long get_incorrect_percent(struct ftrace_branch_data *p)
244{
245    long percent;
246
247    if (p->correct) {
248        percent = p->incorrect * 100;
249        percent /= p->correct + p->incorrect;
250    } else
251        percent = p->incorrect ? 100 : -1;
252
253    return percent;
254}
255
256static int branch_stat_show(struct seq_file *m, void *v)
257{
258    struct ftrace_branch_data *p = v;
259    const char *f;
260    long percent;
261
262    /* Only print the file, not the path */
263    f = p->file + strlen(p->file);
264    while (f >= p->file && *f != '/')
265        f--;
266    f++;
267
268    /*
269     * The miss is overlayed on correct, and hit on incorrect.
270     */
271    percent = get_incorrect_percent(p);
272
273    seq_printf(m, "%8lu %8lu ", p->correct, p->incorrect);
274    if (percent < 0)
275        seq_printf(m, " X ");
276    else
277        seq_printf(m, "%3ld ", percent);
278    seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
279    return 0;
280}
281
282static void *annotated_branch_stat_start(struct tracer_stat *trace)
283{
284    return __start_annotated_branch_profile;
285}
286
287static void *
288annotated_branch_stat_next(void *v, int idx)
289{
290    struct ftrace_branch_data *p = v;
291
292    ++p;
293
294    if ((void *)p >= (void *)__stop_annotated_branch_profile)
295        return NULL;
296
297    return p;
298}
299
300static int annotated_branch_stat_cmp(void *p1, void *p2)
301{
302    struct ftrace_branch_data *a = p1;
303    struct ftrace_branch_data *b = p2;
304
305    long percent_a, percent_b;
306
307    percent_a = get_incorrect_percent(a);
308    percent_b = get_incorrect_percent(b);
309
310    if (percent_a < percent_b)
311        return -1;
312    if (percent_a > percent_b)
313        return 1;
314
315    if (a->incorrect < b->incorrect)
316        return -1;
317    if (a->incorrect > b->incorrect)
318        return 1;
319
320    /*
321     * Since the above shows worse (incorrect) cases
322     * first, we continue that by showing best (correct)
323     * cases last.
324     */
325    if (a->correct > b->correct)
326        return -1;
327    if (a->correct < b->correct)
328        return 1;
329
330    return 0;
331}
332
333static struct tracer_stat annotated_branch_stats = {
334    .name = "branch_annotated",
335    .stat_start = annotated_branch_stat_start,
336    .stat_next = annotated_branch_stat_next,
337    .stat_cmp = annotated_branch_stat_cmp,
338    .stat_headers = annotated_branch_stat_headers,
339    .stat_show = branch_stat_show
340};
341
342__init static int init_annotated_branch_stats(void)
343{
344    int ret;
345
346    ret = register_stat_tracer(&annotated_branch_stats);
347    if (!ret) {
348        printk(KERN_WARNING "Warning: could not register "
349                    "annotated branches stats\n");
350        return 1;
351    }
352    return 0;
353}
354fs_initcall(init_annotated_branch_stats);
355
356#ifdef CONFIG_PROFILE_ALL_BRANCHES
357
358extern unsigned long __start_branch_profile[];
359extern unsigned long __stop_branch_profile[];
360
361static int all_branch_stat_headers(struct seq_file *m)
362{
363    seq_printf(m, " miss hit %% ");
364    seq_printf(m, " Function "
365                  " File Line\n"
366                  " ------- --------- - "
367                  " -------- "
368                  " ---- ----\n");
369    return 0;
370}
371
372static void *all_branch_stat_start(struct tracer_stat *trace)
373{
374    return __start_branch_profile;
375}
376
377static void *
378all_branch_stat_next(void *v, int idx)
379{
380    struct ftrace_branch_data *p = v;
381
382    ++p;
383
384    if ((void *)p >= (void *)__stop_branch_profile)
385        return NULL;
386
387    return p;
388}
389
390static struct tracer_stat all_branch_stats = {
391    .name = "branch_all",
392    .stat_start = all_branch_stat_start,
393    .stat_next = all_branch_stat_next,
394    .stat_headers = all_branch_stat_headers,
395    .stat_show = branch_stat_show
396};
397
398__init static int all_annotated_branch_stats(void)
399{
400    int ret;
401
402    ret = register_stat_tracer(&all_branch_stats);
403    if (!ret) {
404        printk(KERN_WARNING "Warning: could not register "
405                    "all branches stats\n");
406        return 1;
407    }
408    return 0;
409}
410fs_initcall(all_annotated_branch_stats);
411#endif /* CONFIG_PROFILE_ALL_BRANCHES */
412

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