Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
/*
 * 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_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 trace_array_cpu *data;
	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();
	data = per_cpu_ptr(tr->trace_buffer.data, cpu);
	if (atomic_inc_return(&data->disabled) != 1)
		goto out;

	pc = preempt_count();
	buffer = tr->trace_buffer.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 (!call_filter_check_discard(call, entry, buffer, event))
		__buffer_unlock_commit(buffer, event);

 out:
	atomic_dec(&data->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);
}
core_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 */