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