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/uaccess.h>
  11 #include <linux/module.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/hash.h>
  14 #include <linux/fs.h>
  15 #include <asm/local.h>
  16
  17 #include "trace.h"
  18 #include "trace_stat.h"
  19 #include "trace_output.h"
  20
  21 #ifdef CONFIG_BRANCH_TRACER
  22
  23 static struct tracer branch_trace;
  24 static int branch_tracing_enabled __read_mostly;
  25 static DEFINE_MUTEX(branch_tracing_mutex);
  26
  27 static struct trace_array *branch_tracer;
  28
  29 static void
  30 probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  31 {
  32         struct trace_event_call *call = &event_branch;
  33         struct trace_array *tr = branch_tracer;
  34         struct trace_array_cpu *data;
  35         struct ring_buffer_event *event;
  36         struct trace_branch *entry;
  37         struct ring_buffer *buffer;
  38         unsigned long flags;
  39         int pc;
  40         const char *p;
  41
  42         if (current->trace_recursion & TRACE_BRANCH_BIT)
  43                 return;
  44
  45         /*
  46          * I would love to save just the ftrace_likely_data pointer, but
  47          * this code can also be used by modules. Ugly things can happen
  48          * if the module is unloaded, and then we go and read the
  49          * pointer.  This is slower, but much safer.
  50          */
  51
  52         if (unlikely(!tr))
  53                 return;
  54
  55         raw_local_irq_save(flags);
  56         current->trace_recursion |= TRACE_BRANCH_BIT;
  57         data = this_cpu_ptr(tr->trace_buffer.data);
  58         if (atomic_read(&data->disabled))
  59                 goto out;
  60
  61         pc = preempt_count();
  62         buffer = tr->trace_buffer.buffer;
  63         event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
  64                                           sizeof(*entry), flags, pc);
  65         if (!event)
  66                 goto out;
  67
  68         entry   = ring_buffer_event_data(event);
  69
  70         /* Strip off the path, only save the file */
  71         p = f->data.file + strlen(f->data.file);
  72         while (p >= f->data.file && *p != '/')
  73                 p--;
  74         p++;
  75
  76         strncpy(entry->func, f->data.func, TRACE_FUNC_SIZE);
  77         strncpy(entry->file, p, TRACE_FILE_SIZE);
  78         entry->func[TRACE_FUNC_SIZE] = 0;
  79         entry->file[TRACE_FILE_SIZE] = 0;
  80         entry->constant = f->constant;
  81         entry->line = f->data.line;
  82         entry->correct = val == expect;
  83
  84         if (!call_filter_check_discard(call, entry, buffer, event))
  85                 trace_buffer_unlock_commit_nostack(buffer, event);
  86
  87  out:
  88         current->trace_recursion &= ~TRACE_BRANCH_BIT;
  89         raw_local_irq_restore(flags);
  90 }
  91
  92 static inline
  93 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  94 {
  95         if (!branch_tracing_enabled)
  96                 return;
  97
  98         probe_likely_condition(f, val, expect);
  99 }
 100
 101 int enable_branch_tracing(struct trace_array *tr)
 102 {
 103         mutex_lock(&branch_tracing_mutex);
 104         branch_tracer = tr;
 105         /*
 106          * Must be seen before enabling. The reader is a condition
 107          * where we do not need a matching rmb()
 108          */
 109         smp_wmb();
 110         branch_tracing_enabled++;
 111         mutex_unlock(&branch_tracing_mutex);
 112
 113         return 0;
 114 }
 115
 116 void disable_branch_tracing(void)
 117 {
 118         mutex_lock(&branch_tracing_mutex);
 119
 120         if (!branch_tracing_enabled)
 121                 goto out_unlock;
 122
 123         branch_tracing_enabled--;
 124
 125  out_unlock:
 126         mutex_unlock(&branch_tracing_mutex);
 127 }
 128
 129 static int branch_trace_init(struct trace_array *tr)
 130 {
 131         return enable_branch_tracing(tr);
 132 }
 133
 134 static void branch_trace_reset(struct trace_array *tr)
 135 {
 136         disable_branch_tracing();
 137 }
 138
 139 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 140                                             int flags, struct trace_event *event)
 141 {
 142         struct trace_branch *field;
 143
 144         trace_assign_type(field, iter->ent);
 145
 146         trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
 147                          field->correct ? "  ok  " : " MISS ",
 148                          field->func,
 149                          field->file,
 150                          field->line);
 151
 152         return trace_handle_return(&iter->seq);
 153 }
 154
 155 static void branch_print_header(struct seq_file *s)
 156 {
 157         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 158                     "  FUNC:FILE:LINE\n"
 159                     "#              | |       |          |         |   "
 160                     "    |\n");
 161 }
 162
 163 static struct trace_event_functions trace_branch_funcs = {
 164         .trace          = trace_branch_print,
 165 };
 166
 167 static struct trace_event trace_branch_event = {
 168         .type           = TRACE_BRANCH,
 169         .funcs          = &trace_branch_funcs,
 170 };
 171
 172 static struct tracer branch_trace __read_mostly =
 173 {
 174         .name           = "branch",
 175         .init           = branch_trace_init,
 176         .reset          = branch_trace_reset,
 177 #ifdef CONFIG_FTRACE_SELFTEST
 178         .selftest       = trace_selftest_startup_branch,
 179 #endif /* CONFIG_FTRACE_SELFTEST */
 180         .print_header   = branch_print_header,
 181 };
 182
 183 __init static int init_branch_tracer(void)
 184 {
 185         int ret;
 186
 187         ret = register_trace_event(&trace_branch_event);
 188         if (!ret) {
 189                 printk(KERN_WARNING "Warning: could not register "
 190                                     "branch events\n");
 191                 return 1;
 192         }
 193         return register_tracer(&branch_trace);
 194 }
 195 core_initcall(init_branch_tracer);
 196
 197 #else
 198 static inline
 199 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 200 {
 201 }
 202 #endif /* CONFIG_BRANCH_TRACER */
 203
 204 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 205                           int expect, int is_constant)
 206 {
 207         /* A constant is always correct */
 208         if (is_constant) {
 209                 f->constant++;
 210                 val = expect;
 211         }
 212         /*
 213          * I would love to have a trace point here instead, but the
 214          * trace point code is so inundated with unlikely and likely
 215          * conditions that the recursive nightmare that exists is too
 216          * much to try to get working. At least for now.
 217          */
 218         trace_likely_condition(f, val, expect);
 219
 220         /* FIXME: Make this atomic! */
 221         if (val == expect)
 222                 f->data.correct++;
 223         else
 224                 f->data.incorrect++;
 225 }
 226 EXPORT_SYMBOL(ftrace_likely_update);
 227
 228 extern unsigned long __start_annotated_branch_profile[];
 229 extern unsigned long __stop_annotated_branch_profile[];
 230
 231 static int annotated_branch_stat_headers(struct seq_file *m)
 232 {
 233         seq_puts(m, " correct incorrect  % "
 234                     "       Function                "
 235                     "  File              Line\n"
 236                     " ------- ---------  - "
 237                     "       --------                "
 238                     "  ----              ----\n");
 239         return 0;
 240 }
 241
 242 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 243 {
 244         long percent;
 245
 246         if (p->correct) {
 247                 percent = p->incorrect * 100;
 248                 percent /= p->correct + p->incorrect;
 249         } else
 250                 percent = p->incorrect ? 100 : -1;
 251
 252         return percent;
 253 }
 254
 255 static const char *branch_stat_process_file(struct ftrace_branch_data *p)
 256 {
 257         const char *f;
 258
 259         /* Only print the file, not the path */
 260         f = p->file + strlen(p->file);
 261         while (f >= p->file && *f != '/')
 262                 f--;
 263         return ++f;
 264 }
 265
 266 static void branch_stat_show(struct seq_file *m,
 267                              struct ftrace_branch_data *p, const char *f)
 268 {
 269         long percent;
 270
 271         /*
 272          * The miss is overlayed on correct, and hit on incorrect.
 273          */
 274         percent = get_incorrect_percent(p);
 275
 276         if (percent < 0)
 277                 seq_puts(m, "  X ");
 278         else
 279                 seq_printf(m, "%3ld ", percent);
 280
 281         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 282 }
 283
 284 static int branch_stat_show_normal(struct seq_file *m,
 285                                    struct ftrace_branch_data *p, const char *f)
 286 {
 287         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 288         branch_stat_show(m, p, f);
 289         return 0;
 290 }
 291
 292 static int annotate_branch_stat_show(struct seq_file *m, void *v)
 293 {
 294         struct ftrace_likely_data *p = v;
 295         const char *f;
 296         int l;
 297
 298         f = branch_stat_process_file(&p->data);
 299
 300         if (!p->constant)
 301                 return branch_stat_show_normal(m, &p->data, f);
 302
 303         l = snprintf(NULL, 0, "/%lu", p->constant);
 304         l = l > 8 ? 0 : 8 - l;
 305
 306         seq_printf(m, "%8lu/%lu %*lu ",
 307                    p->data.correct, p->constant, l, p->data.incorrect);
 308         branch_stat_show(m, &p->data, f);
 309         return 0;
 310 }
 311
 312 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 313 {
 314         return __start_annotated_branch_profile;
 315 }
 316
 317 static void *
 318 annotated_branch_stat_next(void *v, int idx)
 319 {
 320         struct ftrace_likely_data *p = v;
 321
 322         ++p;
 323
 324         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 325                 return NULL;
 326
 327         return p;
 328 }
 329
 330 static int annotated_branch_stat_cmp(void *p1, void *p2)
 331 {
 332         struct ftrace_branch_data *a = p1;
 333         struct ftrace_branch_data *b = p2;
 334
 335         long percent_a, percent_b;
 336
 337         percent_a = get_incorrect_percent(a);
 338         percent_b = get_incorrect_percent(b);
 339
 340         if (percent_a < percent_b)
 341                 return -1;
 342         if (percent_a > percent_b)
 343                 return 1;
 344
 345         if (a->incorrect < b->incorrect)
 346                 return -1;
 347         if (a->incorrect > b->incorrect)
 348                 return 1;
 349
 350         /*
 351          * Since the above shows worse (incorrect) cases
 352          * first, we continue that by showing best (correct)
 353          * cases last.
 354          */
 355         if (a->correct > b->correct)
 356                 return -1;
 357         if (a->correct < b->correct)
 358                 return 1;
 359
 360         return 0;
 361 }
 362
 363 static struct tracer_stat annotated_branch_stats = {
 364         .name = "branch_annotated",
 365         .stat_start = annotated_branch_stat_start,
 366         .stat_next = annotated_branch_stat_next,
 367         .stat_cmp = annotated_branch_stat_cmp,
 368         .stat_headers = annotated_branch_stat_headers,
 369         .stat_show = annotate_branch_stat_show
 370 };
 371
 372 __init static int init_annotated_branch_stats(void)
 373 {
 374         int ret;
 375
 376         ret = register_stat_tracer(&annotated_branch_stats);
 377         if (!ret) {
 378                 printk(KERN_WARNING "Warning: could not register "
 379                                     "annotated branches stats\n");
 380                 return 1;
 381         }
 382         return 0;
 383 }
 384 fs_initcall(init_annotated_branch_stats);
 385
 386 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 387
 388 extern unsigned long __start_branch_profile[];
 389 extern unsigned long __stop_branch_profile[];
 390
 391 static int all_branch_stat_headers(struct seq_file *m)
 392 {
 393         seq_puts(m, "   miss      hit    % "
 394                     "       Function                "
 395                     "  File              Line\n"
 396                     " ------- ---------  - "
 397                     "       --------                "
 398                     "  ----              ----\n");
 399         return 0;
 400 }
 401
 402 static void *all_branch_stat_start(struct tracer_stat *trace)
 403 {
 404         return __start_branch_profile;
 405 }
 406
 407 static void *
 408 all_branch_stat_next(void *v, int idx)
 409 {
 410         struct ftrace_branch_data *p = v;
 411
 412         ++p;
 413
 414         if ((void *)p >= (void *)__stop_branch_profile)
 415                 return NULL;
 416
 417         return p;
 418 }
 419
 420 static int all_branch_stat_show(struct seq_file *m, void *v)
 421 {
 422         struct ftrace_branch_data *p = v;
 423         const char *f;
 424
 425         f = branch_stat_process_file(p);
 426         return branch_stat_show_normal(m, p, f);
 427 }
 428
 429 static struct tracer_stat all_branch_stats = {
 430         .name = "branch_all",
 431         .stat_start = all_branch_stat_start,
 432         .stat_next = all_branch_stat_next,
 433         .stat_headers = all_branch_stat_headers,
 434         .stat_show = all_branch_stat_show
 435 };
 436
 437 __init static int all_annotated_branch_stats(void)
 438 {
 439         int ret;
 440
 441         ret = register_stat_tracer(&all_branch_stats);
 442         if (!ret) {
 443                 printk(KERN_WARNING "Warning: could not register "
 444                                     "all branches stats\n");
 445                 return 1;
 446         }
 447         return 0;
 448 }
 449 fs_initcall(all_annotated_branch_stats);
 450 #endif /* CONFIG_PROFILE_ALL_BRANCHES */