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
 159 static struct trace_event trace_branch_event = {
 160         .type           = TRACE_BRANCH,
 161         .trace          = trace_branch_print,
 162 };
 163
 164 static struct tracer branch_trace __read_mostly =
 165 {
 166         .name           = "branch",
 167         .init           = branch_trace_init,
 168         .reset          = branch_trace_reset,
 169 #ifdef CONFIG_FTRACE_SELFTEST
 170         .selftest       = trace_selftest_startup_branch,
 171 #endif /* CONFIG_FTRACE_SELFTEST */
 172 };
 173
 174 __init static int init_branch_tracer(void)
 175 {
 176         int ret;
 177
 178         ret = register_ftrace_event(&trace_branch_event);
 179         if (!ret) {
 180                 printk(KERN_WARNING "Warning: could not register "
 181                                     "branch events\n");
 182                 return 1;
 183         }
 184         return register_tracer(&branch_trace);
 185 }
 186 device_initcall(init_branch_tracer);
 187
 188 #else
 189 static inline
 190 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 191 {
 192 }
 193 #endif /* CONFIG_BRANCH_TRACER */
 194
 195 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 196 {
 197         /*
 198          * I would love to have a trace point here instead, but the
 199          * trace point code is so inundated with unlikely and likely
 200          * conditions that the recursive nightmare that exists is too
 201          * much to try to get working. At least for now.
 202          */
 203         trace_likely_condition(f, val, expect);
 204
 205         /* FIXME: Make this atomic! */
 206         if (val == expect)
 207                 f->correct++;
 208         else
 209                 f->incorrect++;
 210 }
 211 EXPORT_SYMBOL(ftrace_likely_update);
 212
 213 extern unsigned long __start_annotated_branch_profile[];
 214 extern unsigned long __stop_annotated_branch_profile[];
 215
 216 static int annotated_branch_stat_headers(struct seq_file *m)
 217 {
 218         seq_printf(m, " correct incorrect  %% ");
 219         seq_printf(m, "       Function                "
 220                               "  File              Line\n"
 221                               " ------- ---------  - "
 222                               "       --------                "
 223                               "  ----              ----\n");
 224         return 0;
 225 }
 226
 227 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 228 {
 229         long percent;
 230
 231         if (p->correct) {
 232                 percent = p->incorrect * 100;
 233                 percent /= p->correct + p->incorrect;
 234         } else
 235                 percent = p->incorrect ? 100 : -1;
 236
 237         return percent;
 238 }
 239
 240 static int branch_stat_show(struct seq_file *m, void *v)
 241 {
 242         struct ftrace_branch_data *p = v;
 243         const char *f;
 244         long percent;
 245
 246         /* Only print the file, not the path */
 247         f = p->file + strlen(p->file);
 248         while (f >= p->file && *f != '/')
 249                 f--;
 250         f++;
 251
 252         /*
 253          * The miss is overlayed on correct, and hit on incorrect.
 254          */
 255         percent = get_incorrect_percent(p);
 256
 257         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 258         if (percent < 0)
 259                 seq_printf(m, "  X ");
 260         else
 261                 seq_printf(m, "%3ld ", percent);
 262         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 263         return 0;
 264 }
 265
 266 static void *annotated_branch_stat_start(void)
 267 {
 268         return __start_annotated_branch_profile;
 269 }
 270
 271 static void *
 272 annotated_branch_stat_next(void *v, int idx)
 273 {
 274         struct ftrace_branch_data *p = v;
 275
 276         ++p;
 277
 278         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 279                 return NULL;
 280
 281         return p;
 282 }
 283
 284 static int annotated_branch_stat_cmp(void *p1, void *p2)
 285 {
 286         struct ftrace_branch_data *a = p1;
 287         struct ftrace_branch_data *b = p2;
 288
 289         long percent_a, percent_b;
 290
 291         percent_a = get_incorrect_percent(a);
 292         percent_b = get_incorrect_percent(b);
 293
 294         if (percent_a < percent_b)
 295                 return -1;
 296         if (percent_a > percent_b)
 297                 return 1;
 298         else
 299                 return 0;
 300 }
 301
 302 static struct tracer_stat annotated_branch_stats = {
 303         .name = "branch_annotated",
 304         .stat_start = annotated_branch_stat_start,
 305         .stat_next = annotated_branch_stat_next,
 306         .stat_cmp = annotated_branch_stat_cmp,
 307         .stat_headers = annotated_branch_stat_headers,
 308         .stat_show = branch_stat_show
 309 };
 310
 311 __init static int init_annotated_branch_stats(void)
 312 {
 313         int ret;
 314
 315         ret = register_stat_tracer(&annotated_branch_stats);
 316         if (!ret) {
 317                 printk(KERN_WARNING "Warning: could not register "
 318                                     "annotated branches stats\n");
 319                 return 1;
 320         }
 321         return 0;
 322 }
 323 fs_initcall(init_annotated_branch_stats);
 324
 325 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 326
 327 extern unsigned long __start_branch_profile[];
 328 extern unsigned long __stop_branch_profile[];
 329
 330 static int all_branch_stat_headers(struct seq_file *m)
 331 {
 332         seq_printf(m, "   miss      hit    %% ");
 333         seq_printf(m, "       Function                "
 334                               "  File              Line\n"
 335                               " ------- ---------  - "
 336                               "       --------                "
 337                               "  ----              ----\n");
 338         return 0;
 339 }
 340
 341 static void *all_branch_stat_start(void)
 342 {
 343         return __start_branch_profile;
 344 }
 345
 346 static void *
 347 all_branch_stat_next(void *v, int idx)
 348 {
 349         struct ftrace_branch_data *p = v;
 350
 351         ++p;
 352
 353         if ((void *)p >= (void *)__stop_branch_profile)
 354                 return NULL;
 355
 356         return p;
 357 }
 358
 359 static struct tracer_stat all_branch_stats = {
 360         .name = "branch_all",
 361         .stat_start = all_branch_stat_start,
 362         .stat_next = all_branch_stat_next,
 363         .stat_headers = all_branch_stat_headers,
 364         .stat_show = branch_stat_show
 365 };
 366
 367 __init static int all_annotated_branch_stats(void)
 368 {
 369         int ret;
 370
 371         ret = register_stat_tracer(&all_branch_stats);
 372         if (!ret) {
 373                 printk(KERN_WARNING "Warning: could not register "
 374                                     "all branches stats\n");
 375                 return 1;
 376         }
 377         return 0;
 378 }
 379 fs_initcall(all_annotated_branch_stats);
 380 #endif /* CONFIG_PROFILE_ALL_BRANCHES */