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