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 enum print_line_t trace_branch_print(struct trace_iterator *iter,
 164                                             int flags)
 165 {
 166         struct trace_branch *field;
 167
 168         trace_assign_type(field, iter->ent);
 169
 170         if (trace_seq_printf(&iter->seq, "[%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 TRACE_TYPE_HANDLED;
 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 };
 186
 187 static struct tracer branch_trace __read_mostly =
 188 {
 189         .name           = "branch",
 190         .init           = branch_trace_init,
 191         .reset          = branch_trace_reset,
 192 #ifdef CONFIG_FTRACE_SELFTEST
 193         .selftest       = trace_selftest_startup_branch,
 194 #endif /* CONFIG_FTRACE_SELFTEST */
 195 };
 196
 197 __init static int init_branch_tracer(void)
 198 {
 199         int ret;
 200
 201         ret = register_ftrace_event(&trace_branch_event);
 202         if (!ret) {
 203                 printk(KERN_WARNING "Warning: could not register "
 204                                     "branch events\n");
 205                 return 1;
 206         }
 207         return register_tracer(&branch_trace);
 208 }
 209 device_initcall(init_branch_tracer);
 210
 211 #else
 212 static inline
 213 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 214 {
 215 }
 216 #endif /* CONFIG_BRANCH_TRACER */
 217
 218 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 219 {
 220         /*
 221          * I would love to have a trace point here instead, but the
 222          * trace point code is so inundated with unlikely and likely
 223          * conditions that the recursive nightmare that exists is too
 224          * much to try to get working. At least for now.
 225          */
 226         trace_likely_condition(f, val, expect);
 227
 228         /* FIXME: Make this atomic! */
 229         if (val == expect)
 230                 f->correct++;
 231         else
 232                 f->incorrect++;
 233 }
 234 EXPORT_SYMBOL(ftrace_likely_update);
 235
 236 extern unsigned long __start_annotated_branch_profile[];
 237 extern unsigned long __stop_annotated_branch_profile[];
 238
 239 static int annotated_branch_stat_headers(struct seq_file *m)
 240 {
 241         seq_printf(m, " correct incorrect  %% ");
 242         seq_printf(m, "       Function                "
 243                               "  File              Line\n"
 244                               " ------- ---------  - "
 245                               "       --------                "
 246                               "  ----              ----\n");
 247         return 0;
 248 }
 249
 250 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 251 {
 252         long percent;
 253
 254         if (p->correct) {
 255                 percent = p->incorrect * 100;
 256                 percent /= p->correct + p->incorrect;
 257         } else
 258                 percent = p->incorrect ? 100 : -1;
 259
 260         return percent;
 261 }
 262
 263 static int branch_stat_show(struct seq_file *m, void *v)
 264 {
 265         struct ftrace_branch_data *p = v;
 266         const char *f;
 267         long percent;
 268
 269         /* Only print the file, not the path */
 270         f = p->file + strlen(p->file);
 271         while (f >= p->file && *f != '/')
 272                 f--;
 273         f++;
 274
 275         /*
 276          * The miss is overlayed on correct, and hit on incorrect.
 277          */
 278         percent = get_incorrect_percent(p);
 279
 280         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 281         if (percent < 0)
 282                 seq_printf(m, "  X ");
 283         else
 284                 seq_printf(m, "%3ld ", percent);
 285         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 286         return 0;
 287 }
 288
 289 static void *annotated_branch_stat_start(void)
 290 {
 291         return __start_annotated_branch_profile;
 292 }
 293
 294 static void *
 295 annotated_branch_stat_next(void *v, int idx)
 296 {
 297         struct ftrace_branch_data *p = v;
 298
 299         ++p;
 300
 301         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 302                 return NULL;
 303
 304         return p;
 305 }
 306
 307 static int annotated_branch_stat_cmp(void *p1, void *p2)
 308 {
 309         struct ftrace_branch_data *a = p1;
 310         struct ftrace_branch_data *b = p2;
 311
 312         long percent_a, percent_b;
 313
 314         percent_a = get_incorrect_percent(a);
 315         percent_b = get_incorrect_percent(b);
 316
 317         if (percent_a < percent_b)
 318                 return -1;
 319         if (percent_a > percent_b)
 320                 return 1;
 321         else
 322                 return 0;
 323 }
 324
 325 static struct tracer_stat annotated_branch_stats = {
 326         .name = "branch_annotated",
 327         .stat_start = annotated_branch_stat_start,
 328         .stat_next = annotated_branch_stat_next,
 329         .stat_cmp = annotated_branch_stat_cmp,
 330         .stat_headers = annotated_branch_stat_headers,
 331         .stat_show = branch_stat_show
 332 };
 333
 334 __init static int init_annotated_branch_stats(void)
 335 {
 336         int ret;
 337
 338         ret = register_stat_tracer(&annotated_branch_stats);
 339         if (!ret) {
 340                 printk(KERN_WARNING "Warning: could not register "
 341                                     "annotated branches stats\n");
 342                 return 1;
 343         }
 344         return 0;
 345 }
 346 fs_initcall(init_annotated_branch_stats);
 347
 348 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 349
 350 extern unsigned long __start_branch_profile[];
 351 extern unsigned long __stop_branch_profile[];
 352
 353 static int all_branch_stat_headers(struct seq_file *m)
 354 {
 355         seq_printf(m, "   miss      hit    %% ");
 356         seq_printf(m, "       Function                "
 357                               "  File              Line\n"
 358                               " ------- ---------  - "
 359                               "       --------                "
 360                               "  ----              ----\n");
 361         return 0;
 362 }
 363
 364 static void *all_branch_stat_start(void)
 365 {
 366         return __start_branch_profile;
 367 }
 368
 369 static void *
 370 all_branch_stat_next(void *v, int idx)
 371 {
 372         struct ftrace_branch_data *p = v;
 373
 374         ++p;
 375
 376         if ((void *)p >= (void *)__stop_branch_profile)
 377                 return NULL;
 378
 379         return p;
 380 }
 381
 382 static struct tracer_stat all_branch_stats = {
 383         .name = "branch_all",
 384         .stat_start = all_branch_stat_start,
 385         .stat_next = all_branch_stat_next,
 386         .stat_headers = all_branch_stat_headers,
 387         .stat_show = branch_stat_show
 388 };
 389
 390 __init static int all_annotated_branch_stats(void)
 391 {
 392         int ret;
 393
 394         ret = register_stat_tracer(&all_branch_stats);
 395         if (!ret) {
 396                 printk(KERN_WARNING "Warning: could not register "
 397                                     "all branches stats\n");
 398                 return 1;
 399         }
 400         return 0;
 401 }
 402 fs_initcall(all_annotated_branch_stats);
 403 #endif /* CONFIG_PROFILE_ALL_BRANCHES */