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, irq_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         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
  56                                          &irq_flags);
  57         if (!event)
  58                 goto out;
  59
  60         pc = preempt_count();
  61         entry   = ring_buffer_event_data(event);
  62         tracing_generic_entry_update(&entry->ent, flags, pc);
  63         entry->ent.type         = TRACE_BRANCH;
  64
  65         /* Strip off the path, only save the file */
  66         p = f->file + strlen(f->file);
  67         while (p >= f->file && *p != '/')
  68                 p--;
  69         p++;
  70
  71         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  72         strncpy(entry->file, p, TRACE_FILE_SIZE);
  73         entry->func[TRACE_FUNC_SIZE] = 0;
  74         entry->file[TRACE_FILE_SIZE] = 0;
  75         entry->line = f->line;
  76         entry->correct = val == expect;
  77
  78         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
  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         int ret = 0;
  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 ret;
 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         tracing_reset_online_cpus(tr);
 137         start_branch_trace(tr);
 138         return 0;
 139 }
 140
 141 static void branch_trace_reset(struct trace_array *tr)
 142 {
 143         stop_branch_trace(tr);
 144 }
 145
 146 static int
 147 trace_print_print(struct trace_seq *s, struct trace_entry *entry, int flags)
 148 {
 149         struct print_entry *field;
 150
 151         trace_assign_type(field, entry);
 152
 153         if (seq_print_ip_sym(s, field->ip, flags))
 154                 goto partial;
 155
 156         if (trace_seq_printf(s, ": %s", field->buf))
 157                 goto partial;
 158
 159  partial:
 160         return TRACE_TYPE_PARTIAL_LINE;
 161 }
 162
 163 static int
 164 trace_branch_print(struct trace_seq *s, struct trace_entry *entry, int flags)
 165 {
 166         struct trace_branch *field;
 167
 168         trace_assign_type(field, entry);
 169
 170         if (trace_seq_printf(s, "[%s] %s:%s:%d\n",
 171                              field->correct ? "  ok  " : " MISS ",
 172                              field->func,
 173                              field->file,
 174                              field->line))
 175                 return TRACE_TYPE_PARTIAL_LINE;
 176
 177         return 0;
 178 }
 179
 180
 181 static struct trace_event trace_branch_event = {
 182         .type           = TRACE_BRANCH,
 183         .trace          = trace_branch_print,
 184         .latency_trace  = trace_branch_print,
 185         .raw            = trace_nop_print,
 186         .hex            = trace_nop_print,
 187         .binary         = trace_nop_print,
 188 };
 189
 190 static struct tracer branch_trace __read_mostly =
 191 {
 192         .name           = "branch",
 193         .init           = branch_trace_init,
 194         .reset          = branch_trace_reset,
 195 #ifdef CONFIG_FTRACE_SELFTEST
 196         .selftest       = trace_selftest_startup_branch,
 197 #endif /* CONFIG_FTRACE_SELFTEST */
 198 };
 199
 200 __init static int init_branch_tracer(void)
 201 {
 202         int ret;
 203
 204         ret = register_ftrace_event(&trace_branch_event);
 205         if (!ret) {
 206                 printk(KERN_WARNING "Warning: could not register "
 207                                     "branch events\n");
 208                 return 1;
 209         }
 210         return register_tracer(&branch_trace);
 211 }
 212 device_initcall(init_branch_tracer);
 213
 214 #else
 215 static inline
 216 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 217 {
 218 }
 219 #endif /* CONFIG_BRANCH_TRACER */
 220
 221 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 222 {
 223         /*
 224          * I would love to have a trace point here instead, but the
 225          * trace point code is so inundated with unlikely and likely
 226          * conditions that the recursive nightmare that exists is too
 227          * much to try to get working. At least for now.
 228          */
 229         trace_likely_condition(f, val, expect);
 230
 231         /* FIXME: Make this atomic! */
 232         if (val == expect)
 233                 f->correct++;
 234         else
 235                 f->incorrect++;
 236 }
 237 EXPORT_SYMBOL(ftrace_likely_update);
 238
 239 extern unsigned long __start_annotated_branch_profile[];
 240 extern unsigned long __stop_annotated_branch_profile[];
 241
 242 static int annotated_branch_stat_headers(struct seq_file *m)
 243 {
 244         seq_printf(m, " correct incorrect  %% ");
 245         seq_printf(m, "       Function                "
 246                               "  File              Line\n"
 247                               " ------- ---------  - "
 248                               "       --------                "
 249                               "  ----              ----\n");
 250         return 0;
 251 }
 252
 253 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 254 {
 255         long percent;
 256
 257         if (p->correct) {
 258                 percent = p->incorrect * 100;
 259                 percent /= p->correct + p->incorrect;
 260         } else
 261                 percent = p->incorrect ? 100 : -1;
 262
 263         return percent;
 264 }
 265
 266 static int branch_stat_show(struct seq_file *m, void *v)
 267 {
 268         struct ftrace_branch_data *p = v;
 269         const char *f;
 270         long percent;
 271
 272         /* Only print the file, not the path */
 273         f = p->file + strlen(p->file);
 274         while (f >= p->file && *f != '/')
 275                 f--;
 276         f++;
 277
 278         /*
 279          * The miss is overlayed on correct, and hit on incorrect.
 280          */
 281         percent = get_incorrect_percent(p);
 282
 283         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 284         if (percent < 0)
 285                 seq_printf(m, "  X ");
 286         else
 287                 seq_printf(m, "%3ld ", percent);
 288         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 289         return 0;
 290 }
 291
 292 static void *annotated_branch_stat_start(void)
 293 {
 294         return __start_annotated_branch_profile;
 295 }
 296
 297 static void *
 298 annotated_branch_stat_next(void *v, int idx)
 299 {
 300         struct ftrace_branch_data *p = v;
 301
 302         ++p;
 303
 304         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 305                 return NULL;
 306
 307         return p;
 308 }
 309
 310 static int annotated_branch_stat_cmp(void *p1, void *p2)
 311 {
 312         struct ftrace_branch_data *a = p1;
 313         struct ftrace_branch_data *b = p2;
 314
 315         long percent_a, percent_b;
 316
 317         percent_a = get_incorrect_percent(a);
 318         percent_b = get_incorrect_percent(b);
 319
 320         if (percent_a < percent_b)
 321                 return -1;
 322         if (percent_a > percent_b)
 323                 return 1;
 324         else
 325                 return 0;
 326 }
 327
 328 static struct tracer_stat annotated_branch_stats = {
 329         .name = "branch_annotated",
 330         .stat_start = annotated_branch_stat_start,
 331         .stat_next = annotated_branch_stat_next,
 332         .stat_cmp = annotated_branch_stat_cmp,
 333         .stat_headers = annotated_branch_stat_headers,
 334         .stat_show = branch_stat_show
 335 };
 336
 337 __init static int init_annotated_branch_stats(void)
 338 {
 339         int ret;
 340
 341         ret = register_stat_tracer(&annotated_branch_stats);
 342         if (!ret) {
 343                 printk(KERN_WARNING "Warning: could not register "
 344                                     "annotated branches stats\n");
 345                 return 1;
 346         }
 347         return 0;
 348 }
 349 fs_initcall(init_annotated_branch_stats);
 350
 351 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 352
 353 extern unsigned long __start_branch_profile[];
 354 extern unsigned long __stop_branch_profile[];
 355
 356 static int all_branch_stat_headers(struct seq_file *m)
 357 {
 358         seq_printf(m, "   miss      hit    %% ");
 359         seq_printf(m, "       Function                "
 360                               "  File              Line\n"
 361                               " ------- ---------  - "
 362                               "       --------                "
 363                               "  ----              ----\n");
 364         return 0;
 365 }
 366
 367 static void *all_branch_stat_start(void)
 368 {
 369         return __start_branch_profile;
 370 }
 371
 372 static void *
 373 all_branch_stat_next(void *v, int idx)
 374 {
 375         struct ftrace_branch_data *p = v;
 376
 377         ++p;
 378
 379         if ((void *)p >= (void *)__stop_branch_profile)
 380                 return NULL;
 381
 382         return p;
 383 }
 384
 385 static struct tracer_stat all_branch_stats = {
 386         .name = "branch_all",
 387         .stat_start = all_branch_stat_start,
 388         .stat_next = all_branch_stat_next,
 389         .stat_headers = all_branch_stat_headers,
 390         .stat_show = branch_stat_show
 391 };
 392
 393 __init static int all_annotated_branch_stats(void)
 394 {
 395         int ret;
 396
 397         ret = register_stat_tracer(&all_branch_stats);
 398         if (!ret) {
 399                 printk(KERN_WARNING "Warning: could not register "
 400                                     "all branches stats\n");
 401                 return 1;
 402         }
 403         return 0;
 404 }
 405 fs_initcall(all_annotated_branch_stats);
 406 #endif /* CONFIG_PROFILE_ALL_BRANCHES */