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_branch_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->file + strlen(f->file);
  72         while (p >= f->file && *p != '/')
  73                 p--;
  74         p++;
  75
  76         strncpy(entry->func, f->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->line = f->line;
  81         entry->correct = val == expect;
  82
  83         if (!call_filter_check_discard(call, entry, buffer, event))
  84                 __buffer_unlock_commit(buffer, event);
  85
  86  out:
  87         current->trace_recursion &= ~TRACE_BRANCH_BIT;
  88         raw_local_irq_restore(flags);
  89 }
  90
  91 static inline
  92 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  93 {
  94         if (!branch_tracing_enabled)
  95                 return;
  96
  97         probe_likely_condition(f, val, expect);
  98 }
  99
 100 int enable_branch_tracing(struct trace_array *tr)
 101 {
 102         mutex_lock(&branch_tracing_mutex);
 103         branch_tracer = tr;
 104         /*
 105          * Must be seen before enabling. The reader is a condition
 106          * where we do not need a matching rmb()
 107          */
 108         smp_wmb();
 109         branch_tracing_enabled++;
 110         mutex_unlock(&branch_tracing_mutex);
 111
 112         return 0;
 113 }
 114
 115 void disable_branch_tracing(void)
 116 {
 117         mutex_lock(&branch_tracing_mutex);
 118
 119         if (!branch_tracing_enabled)
 120                 goto out_unlock;
 121
 122         branch_tracing_enabled--;
 123
 124  out_unlock:
 125         mutex_unlock(&branch_tracing_mutex);
 126 }
 127
 128 static void start_branch_trace(struct trace_array *tr)
 129 {
 130         enable_branch_tracing(tr);
 131 }
 132
 133 static void stop_branch_trace(struct trace_array *tr)
 134 {
 135         disable_branch_tracing();
 136 }
 137
 138 static int branch_trace_init(struct trace_array *tr)
 139 {
 140         start_branch_trace(tr);
 141         return 0;
 142 }
 143
 144 static void branch_trace_reset(struct trace_array *tr)
 145 {
 146         stop_branch_trace(tr);
 147 }
 148
 149 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 150                                             int flags, struct trace_event *event)
 151 {
 152         struct trace_branch *field;
 153
 154         trace_assign_type(field, iter->ent);
 155
 156         trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
 157                          field->correct ? "  ok  " : " MISS ",
 158                          field->func,
 159                          field->file,
 160                          field->line);
 161
 162         return trace_handle_return(&iter->seq);
 163 }
 164
 165 static void branch_print_header(struct seq_file *s)
 166 {
 167         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 168                     "  FUNC:FILE:LINE\n"
 169                     "#              | |       |          |         |   "
 170                     "    |\n");
 171 }
 172
 173 static struct trace_event_functions trace_branch_funcs = {
 174         .trace          = trace_branch_print,
 175 };
 176
 177 static struct trace_event trace_branch_event = {
 178         .type           = TRACE_BRANCH,
 179         .funcs          = &trace_branch_funcs,
 180 };
 181
 182 static struct tracer branch_trace __read_mostly =
 183 {
 184         .name           = "branch",
 185         .init           = branch_trace_init,
 186         .reset          = branch_trace_reset,
 187 #ifdef CONFIG_FTRACE_SELFTEST
 188         .selftest       = trace_selftest_startup_branch,
 189 #endif /* CONFIG_FTRACE_SELFTEST */
 190         .print_header   = branch_print_header,
 191 };
 192
 193 __init static int init_branch_tracer(void)
 194 {
 195         int ret;
 196
 197         ret = register_trace_event(&trace_branch_event);
 198         if (!ret) {
 199                 printk(KERN_WARNING "Warning: could not register "
 200                                     "branch events\n");
 201                 return 1;
 202         }
 203         return register_tracer(&branch_trace);
 204 }
 205 core_initcall(init_branch_tracer);
 206
 207 #else
 208 static inline
 209 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 210 {
 211 }
 212 #endif /* CONFIG_BRANCH_TRACER */
 213
 214 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 215 {
 216         /*
 217          * I would love to have a trace point here instead, but the
 218          * trace point code is so inundated with unlikely and likely
 219          * conditions that the recursive nightmare that exists is too
 220          * much to try to get working. At least for now.
 221          */
 222         trace_likely_condition(f, val, expect);
 223
 224         /* FIXME: Make this atomic! */
 225         if (val == expect)
 226                 f->correct++;
 227         else
 228                 f->incorrect++;
 229 }
 230 EXPORT_SYMBOL(ftrace_likely_update);
 231
 232 extern unsigned long __start_annotated_branch_profile[];
 233 extern unsigned long __stop_annotated_branch_profile[];
 234
 235 static int annotated_branch_stat_headers(struct seq_file *m)
 236 {
 237         seq_puts(m, " correct incorrect  % "
 238                     "       Function                "
 239                     "  File              Line\n"
 240                     " ------- ---------  - "
 241                     "       --------                "
 242                     "  ----              ----\n");
 243         return 0;
 244 }
 245
 246 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 247 {
 248         long percent;
 249
 250         if (p->correct) {
 251                 percent = p->incorrect * 100;
 252                 percent /= p->correct + p->incorrect;
 253         } else
 254                 percent = p->incorrect ? 100 : -1;
 255
 256         return percent;
 257 }
 258
 259 static int branch_stat_show(struct seq_file *m, void *v)
 260 {
 261         struct ftrace_branch_data *p = v;
 262         const char *f;
 263         long percent;
 264
 265         /* Only print the file, not the path */
 266         f = p->file + strlen(p->file);
 267         while (f >= p->file && *f != '/')
 268                 f--;
 269         f++;
 270
 271         /*
 272          * The miss is overlayed on correct, and hit on incorrect.
 273          */
 274         percent = get_incorrect_percent(p);
 275
 276         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 277         if (percent < 0)
 278                 seq_puts(m, "  X ");
 279         else
 280                 seq_printf(m, "%3ld ", percent);
 281         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 282         return 0;
 283 }
 284
 285 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 286 {
 287         return __start_annotated_branch_profile;
 288 }
 289
 290 static void *
 291 annotated_branch_stat_next(void *v, int idx)
 292 {
 293         struct ftrace_branch_data *p = v;
 294
 295         ++p;
 296
 297         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 298                 return NULL;
 299
 300         return p;
 301 }
 302
 303 static int annotated_branch_stat_cmp(void *p1, void *p2)
 304 {
 305         struct ftrace_branch_data *a = p1;
 306         struct ftrace_branch_data *b = p2;
 307
 308         long percent_a, percent_b;
 309
 310         percent_a = get_incorrect_percent(a);
 311         percent_b = get_incorrect_percent(b);
 312
 313         if (percent_a < percent_b)
 314                 return -1;
 315         if (percent_a > percent_b)
 316                 return 1;
 317
 318         if (a->incorrect < b->incorrect)
 319                 return -1;
 320         if (a->incorrect > b->incorrect)
 321                 return 1;
 322
 323         /*
 324          * Since the above shows worse (incorrect) cases
 325          * first, we continue that by showing best (correct)
 326          * cases last.
 327          */
 328         if (a->correct > b->correct)
 329                 return -1;
 330         if (a->correct < b->correct)
 331                 return 1;
 332
 333         return 0;
 334 }
 335
 336 static struct tracer_stat annotated_branch_stats = {
 337         .name = "branch_annotated",
 338         .stat_start = annotated_branch_stat_start,
 339         .stat_next = annotated_branch_stat_next,
 340         .stat_cmp = annotated_branch_stat_cmp,
 341         .stat_headers = annotated_branch_stat_headers,
 342         .stat_show = branch_stat_show
 343 };
 344
 345 __init static int init_annotated_branch_stats(void)
 346 {
 347         int ret;
 348
 349         ret = register_stat_tracer(&annotated_branch_stats);
 350         if (!ret) {
 351                 printk(KERN_WARNING "Warning: could not register "
 352                                     "annotated branches stats\n");
 353                 return 1;
 354         }
 355         return 0;
 356 }
 357 fs_initcall(init_annotated_branch_stats);
 358
 359 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 360
 361 extern unsigned long __start_branch_profile[];
 362 extern unsigned long __stop_branch_profile[];
 363
 364 static int all_branch_stat_headers(struct seq_file *m)
 365 {
 366         seq_puts(m, "   miss      hit    % "
 367                     "       Function                "
 368                     "  File              Line\n"
 369                     " ------- ---------  - "
 370                     "       --------                "
 371                     "  ----              ----\n");
 372         return 0;
 373 }
 374
 375 static void *all_branch_stat_start(struct tracer_stat *trace)
 376 {
 377         return __start_branch_profile;
 378 }
 379
 380 static void *
 381 all_branch_stat_next(void *v, int idx)
 382 {
 383         struct ftrace_branch_data *p = v;
 384
 385         ++p;
 386
 387         if ((void *)p >= (void *)__stop_branch_profile)
 388                 return NULL;
 389
 390         return p;
 391 }
 392
 393 static struct tracer_stat all_branch_stats = {
 394         .name = "branch_all",
 395         .stat_start = all_branch_stat_start,
 396         .stat_next = all_branch_stat_next,
 397         .stat_headers = all_branch_stat_headers,
 398         .stat_show = branch_stat_show
 399 };
 400
 401 __init static int all_annotated_branch_stats(void)
 402 {
 403         int ret;
 404
 405         ret = register_stat_tracer(&all_branch_stats);
 406         if (!ret) {
 407                 printk(KERN_WARNING "Warning: could not register "
 408                                     "all branches stats\n");
 409                 return 1;
 410         }
 411         return 0;
 412 }
 413 fs_initcall(all_annotated_branch_stats);
 414 #endif /* CONFIG_PROFILE_ALL_BRANCHES */