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 static void branch_print_header(struct seq_file *s)
 161 {
 162         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 163                 "  FUNC:FILE:LINE\n");
 164         seq_puts(s, "#              | |       |          |         |   "
 165                 "    |\n");
 166 }
 167
 168 static struct trace_event trace_branch_event = {
 169         .type           = TRACE_BRANCH,
 170         .trace          = trace_branch_print,
 171 };
 172
 173 static struct tracer branch_trace __read_mostly =
 174 {
 175         .name           = "branch",
 176         .init           = branch_trace_init,
 177         .reset          = branch_trace_reset,
 178 #ifdef CONFIG_FTRACE_SELFTEST
 179         .selftest       = trace_selftest_startup_branch,
 180 #endif /* CONFIG_FTRACE_SELFTEST */
 181         .print_header   = branch_print_header,
 182 };
 183
 184 __init static int init_branch_tracer(void)
 185 {
 186         int ret;
 187
 188         ret = register_ftrace_event(&trace_branch_event);
 189         if (!ret) {
 190                 printk(KERN_WARNING "Warning: could not register "
 191                                     "branch events\n");
 192                 return 1;
 193         }
 194         return register_tracer(&branch_trace);
 195 }
 196 device_initcall(init_branch_tracer);
 197
 198 #else
 199 static inline
 200 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 201 {
 202 }
 203 #endif /* CONFIG_BRANCH_TRACER */
 204
 205 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 206 {
 207         /*
 208          * I would love to have a trace point here instead, but the
 209          * trace point code is so inundated with unlikely and likely
 210          * conditions that the recursive nightmare that exists is too
 211          * much to try to get working. At least for now.
 212          */
 213         trace_likely_condition(f, val, expect);
 214
 215         /* FIXME: Make this atomic! */
 216         if (val == expect)
 217                 f->correct++;
 218         else
 219                 f->incorrect++;
 220 }
 221 EXPORT_SYMBOL(ftrace_likely_update);
 222
 223 extern unsigned long __start_annotated_branch_profile[];
 224 extern unsigned long __stop_annotated_branch_profile[];
 225
 226 static int annotated_branch_stat_headers(struct seq_file *m)
 227 {
 228         seq_printf(m, " correct incorrect  %% ");
 229         seq_printf(m, "       Function                "
 230                               "  File              Line\n"
 231                               " ------- ---------  - "
 232                               "       --------                "
 233                               "  ----              ----\n");
 234         return 0;
 235 }
 236
 237 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 238 {
 239         long percent;
 240
 241         if (p->correct) {
 242                 percent = p->incorrect * 100;
 243                 percent /= p->correct + p->incorrect;
 244         } else
 245                 percent = p->incorrect ? 100 : -1;
 246
 247         return percent;
 248 }
 249
 250 static int branch_stat_show(struct seq_file *m, void *v)
 251 {
 252         struct ftrace_branch_data *p = v;
 253         const char *f;
 254         long percent;
 255
 256         /* Only print the file, not the path */
 257         f = p->file + strlen(p->file);
 258         while (f >= p->file && *f != '/')
 259                 f--;
 260         f++;
 261
 262         /*
 263          * The miss is overlayed on correct, and hit on incorrect.
 264          */
 265         percent = get_incorrect_percent(p);
 266
 267         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 268         if (percent < 0)
 269                 seq_printf(m, "  X ");
 270         else
 271                 seq_printf(m, "%3ld ", percent);
 272         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 273         return 0;
 274 }
 275
 276 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 277 {
 278         return __start_annotated_branch_profile;
 279 }
 280
 281 static void *
 282 annotated_branch_stat_next(void *v, int idx)
 283 {
 284         struct ftrace_branch_data *p = v;
 285
 286         ++p;
 287
 288         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 289                 return NULL;
 290
 291         return p;
 292 }
 293
 294 static int annotated_branch_stat_cmp(void *p1, void *p2)
 295 {
 296         struct ftrace_branch_data *a = p1;
 297         struct ftrace_branch_data *b = p2;
 298
 299         long percent_a, percent_b;
 300
 301         percent_a = get_incorrect_percent(a);
 302         percent_b = get_incorrect_percent(b);
 303
 304         if (percent_a < percent_b)
 305                 return -1;
 306         if (percent_a > percent_b)
 307                 return 1;
 308         else
 309                 return 0;
 310 }
 311
 312 static struct tracer_stat annotated_branch_stats = {
 313         .name = "branch_annotated",
 314         .stat_start = annotated_branch_stat_start,
 315         .stat_next = annotated_branch_stat_next,
 316         .stat_cmp = annotated_branch_stat_cmp,
 317         .stat_headers = annotated_branch_stat_headers,
 318         .stat_show = branch_stat_show
 319 };
 320
 321 __init static int init_annotated_branch_stats(void)
 322 {
 323         int ret;
 324
 325         ret = register_stat_tracer(&annotated_branch_stats);
 326         if (!ret) {
 327                 printk(KERN_WARNING "Warning: could not register "
 328                                     "annotated branches stats\n");
 329                 return 1;
 330         }
 331         return 0;
 332 }
 333 fs_initcall(init_annotated_branch_stats);
 334
 335 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 336
 337 extern unsigned long __start_branch_profile[];
 338 extern unsigned long __stop_branch_profile[];
 339
 340 static int all_branch_stat_headers(struct seq_file *m)
 341 {
 342         seq_printf(m, "   miss      hit    %% ");
 343         seq_printf(m, "       Function                "
 344                               "  File              Line\n"
 345                               " ------- ---------  - "
 346                               "       --------                "
 347                               "  ----              ----\n");
 348         return 0;
 349 }
 350
 351 static void *all_branch_stat_start(struct tracer_stat *trace)
 352 {
 353         return __start_branch_profile;
 354 }
 355
 356 static void *
 357 all_branch_stat_next(void *v, int idx)
 358 {
 359         struct ftrace_branch_data *p = v;
 360
 361         ++p;
 362
 363         if ((void *)p >= (void *)__stop_branch_profile)
 364                 return NULL;
 365
 366         return p;
 367 }
 368
 369 static struct tracer_stat all_branch_stats = {
 370         .name = "branch_all",
 371         .stat_start = all_branch_stat_start,
 372         .stat_next = all_branch_stat_next,
 373         .stat_headers = all_branch_stat_headers,
 374         .stat_show = branch_stat_show
 375 };
 376
 377 __init static int all_annotated_branch_stats(void)
 378 {
 379         int ret;
 380
 381         ret = register_stat_tracer(&all_branch_stats);
 382         if (!ret) {
 383                 printk(KERN_WARNING "Warning: could not register "
 384                                     "all branches stats\n");
 385                 return 1;
 386         }
 387         return 0;
 388 }
 389 fs_initcall(all_annotated_branch_stats);
 390 #endif /* CONFIG_PROFILE_ALL_BRANCHES */