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