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 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
  87 static inline
  88 void 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
  96 int 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
 111 void 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
 124 static void start_branch_trace(struct trace_array *tr)
 125 {
 126         enable_branch_tracing(tr);
 127 }
 128
 129 static void stop_branch_trace(struct trace_array *tr)
 130 {
 131         disable_branch_tracing();
 132 }
 133
 134 static int branch_trace_init(struct trace_array *tr)
 135 {
 136         start_branch_trace(tr);
 137         return 0;
 138 }
 139
 140 static void branch_trace_reset(struct trace_array *tr)
 141 {
 142         stop_branch_trace(tr);
 143 }
 144
 145 static 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
 162 static 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
 170 static struct trace_event_functions trace_branch_funcs = {
 171         .trace          = trace_branch_print,
 172 };
 173
 174 static struct trace_event trace_branch_event = {
 175         .type           = TRACE_BRANCH,
 176         .funcs          = &trace_branch_funcs,
 177 };
 178
 179 static 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 }
 202 device_initcall(init_branch_tracer);
 203
 204 #else
 205 static inline
 206 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 207 {
 208 }
 209 #endif /* CONFIG_BRANCH_TRACER */
 210
 211 void 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 }
 227 EXPORT_SYMBOL(ftrace_likely_update);
 228
 229 extern unsigned long __start_annotated_branch_profile[];
 230 extern unsigned long __stop_annotated_branch_profile[];
 231
 232 static 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
 243 static 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
 256 static 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
 282 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 283 {
 284         return __start_annotated_branch_profile;
 285 }
 286
 287 static void *
 288 annotated_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
 300 static 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
 333 static 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 }
 354 fs_initcall(init_annotated_branch_stats);
 355
 356 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 357
 358 extern unsigned long __start_branch_profile[];
 359 extern unsigned long __stop_branch_profile[];
 360
 361 static 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
 372 static void *all_branch_stat_start(struct tracer_stat *trace)
 373 {
 374         return __start_branch_profile;
 375 }
 376
 377 static void *
 378 all_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
 390 static 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 }
 410 fs_initcall(all_annotated_branch_stats);
 411 #endif /* CONFIG_PROFILE_ALL_BRANCHES */