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