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/uaccess.h>
  11 #include <linux/module.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/hash.h>
  14 #include <linux/fs.h>
  15 #include <asm/local.h>
  16
  17 #include "trace.h"
  18 #include "trace_stat.h"
  19 #include "trace_output.h"
  20
  21 #ifdef CONFIG_BRANCH_TRACER
  22
  23 static struct tracer branch_trace;
  24 static int branch_tracing_enabled __read_mostly;
  25 static DEFINE_MUTEX(branch_tracing_mutex);
  26
  27 static struct trace_array *branch_tracer;
  28
  29 static void
  30 probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  31 {
  32         struct trace_event_call *call = &event_branch;
  33         struct trace_array *tr = branch_tracer;
  34         struct trace_array_cpu *data;
  35         struct ring_buffer_event *event;
  36         struct trace_branch *entry;
  37         struct ring_buffer *buffer;
  38         unsigned long flags;
  39         int pc;
  40         const char *p;
  41
  42         if (current->trace_recursion & TRACE_BRANCH_BIT)
  43                 return;
  44
  45         /*
  46          * I would love to save just the ftrace_likely_data pointer, but
  47          * this code can also be used by modules. Ugly things can happen
  48          * if the module is unloaded, and then we go and read the
  49          * pointer.  This is slower, but much safer.
  50          */
  51
  52         if (unlikely(!tr))
  53                 return;
  54
  55         raw_local_irq_save(flags);
  56         current->trace_recursion |= TRACE_BRANCH_BIT;
  57         data = this_cpu_ptr(tr->trace_buffer.data);
  58         if (atomic_read(&data->disabled))
  59                 goto out;
  60
  61         pc = preempt_count();
  62         buffer = tr->trace_buffer.buffer;
  63         event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
  64                                           sizeof(*entry), flags, pc);
  65         if (!event)
  66                 goto out;
  67
  68         entry   = ring_buffer_event_data(event);
  69
  70         /* Strip off the path, only save the file */
  71         p = f->file + strlen(f->file);
  72         while (p >= f->file && *p != '/')
  73                 p--;
  74         p++;
  75
  76         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  77         strncpy(entry->file, p, TRACE_FILE_SIZE);
  78         entry->func[TRACE_FUNC_SIZE] = 0;
  79         entry->file[TRACE_FILE_SIZE] = 0;
  80         entry->line = f->line;
  81         entry->correct = val == expect;
  82
  83         if (!call_filter_check_discard(call, entry, buffer, event))
  84                 trace_buffer_unlock_commit_nostack(buffer, event);
  85
  86  out:
  87         current->trace_recursion &= ~TRACE_BRANCH_BIT;
  88         raw_local_irq_restore(flags);
  89 }
  90
  91 static inline
  92 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  93 {
  94         if (!branch_tracing_enabled)
  95                 return;
  96
  97         probe_likely_condition(f, val, expect);
  98 }
  99
 100 int enable_branch_tracing(struct trace_array *tr)
 101 {
 102         mutex_lock(&branch_tracing_mutex);
 103         branch_tracer = tr;
 104         /*
 105          * Must be seen before enabling. The reader is a condition
 106          * where we do not need a matching rmb()
 107          */
 108         smp_wmb();
 109         branch_tracing_enabled++;
 110         mutex_unlock(&branch_tracing_mutex);
 111
 112         return 0;
 113 }
 114
 115 void disable_branch_tracing(void)
 116 {
 117         mutex_lock(&branch_tracing_mutex);
 118
 119         if (!branch_tracing_enabled)
 120                 goto out_unlock;
 121
 122         branch_tracing_enabled--;
 123
 124  out_unlock:
 125         mutex_unlock(&branch_tracing_mutex);
 126 }
 127
 128 static int branch_trace_init(struct trace_array *tr)
 129 {
 130         return enable_branch_tracing(tr);
 131 }
 132
 133 static void branch_trace_reset(struct trace_array *tr)
 134 {
 135         disable_branch_tracing();
 136 }
 137
 138 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 139                                             int flags, struct trace_event *event)
 140 {
 141         struct trace_branch *field;
 142
 143         trace_assign_type(field, iter->ent);
 144
 145         trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
 146                          field->correct ? "  ok  " : " MISS ",
 147                          field->func,
 148                          field->file,
 149                          field->line);
 150
 151         return trace_handle_return(&iter->seq);
 152 }
 153
 154 static void branch_print_header(struct seq_file *s)
 155 {
 156         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 157                     "  FUNC:FILE:LINE\n"
 158                     "#              | |       |          |         |   "
 159                     "    |\n");
 160 }
 161
 162 static struct trace_event_functions trace_branch_funcs = {
 163         .trace          = trace_branch_print,
 164 };
 165
 166 static struct trace_event trace_branch_event = {
 167         .type           = TRACE_BRANCH,
 168         .funcs          = &trace_branch_funcs,
 169 };
 170
 171 static struct tracer branch_trace __read_mostly =
 172 {
 173         .name           = "branch",
 174         .init           = branch_trace_init,
 175         .reset          = branch_trace_reset,
 176 #ifdef CONFIG_FTRACE_SELFTEST
 177         .selftest       = trace_selftest_startup_branch,
 178 #endif /* CONFIG_FTRACE_SELFTEST */
 179         .print_header   = branch_print_header,
 180 };
 181
 182 __init static int init_branch_tracer(void)
 183 {
 184         int ret;
 185
 186         ret = register_trace_event(&trace_branch_event);
 187         if (!ret) {
 188                 printk(KERN_WARNING "Warning: could not register "
 189                                     "branch events\n");
 190                 return 1;
 191         }
 192         return register_tracer(&branch_trace);
 193 }
 194 core_initcall(init_branch_tracer);
 195
 196 #else
 197 static inline
 198 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 199 {
 200 }
 201 #endif /* CONFIG_BRANCH_TRACER */
 202
 203 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 204 {
 205         /*
 206          * I would love to have a trace point here instead, but the
 207          * trace point code is so inundated with unlikely and likely
 208          * conditions that the recursive nightmare that exists is too
 209          * much to try to get working. At least for now.
 210          */
 211         trace_likely_condition(f, val, expect);
 212
 213         /* FIXME: Make this atomic! */
 214         if (val == expect)
 215                 f->correct++;
 216         else
 217                 f->incorrect++;
 218 }
 219 EXPORT_SYMBOL(ftrace_likely_update);
 220
 221 extern unsigned long __start_annotated_branch_profile[];
 222 extern unsigned long __stop_annotated_branch_profile[];
 223
 224 static int annotated_branch_stat_headers(struct seq_file *m)
 225 {
 226         seq_puts(m, " correct incorrect  % "
 227                     "       Function                "
 228                     "  File              Line\n"
 229                     " ------- ---------  - "
 230                     "       --------                "
 231                     "  ----              ----\n");
 232         return 0;
 233 }
 234
 235 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 236 {
 237         long percent;
 238
 239         if (p->correct) {
 240                 percent = p->incorrect * 100;
 241                 percent /= p->correct + p->incorrect;
 242         } else
 243                 percent = p->incorrect ? 100 : -1;
 244
 245         return percent;
 246 }
 247
 248 static int branch_stat_show(struct seq_file *m, void *v)
 249 {
 250         struct ftrace_branch_data *p = v;
 251         const char *f;
 252         long percent;
 253
 254         /* Only print the file, not the path */
 255         f = p->file + strlen(p->file);
 256         while (f >= p->file && *f != '/')
 257                 f--;
 258         f++;
 259
 260         /*
 261          * The miss is overlayed on correct, and hit on incorrect.
 262          */
 263         percent = get_incorrect_percent(p);
 264
 265         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 266         if (percent < 0)
 267                 seq_puts(m, "  X ");
 268         else
 269                 seq_printf(m, "%3ld ", percent);
 270         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 271         return 0;
 272 }
 273
 274 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 275 {
 276         return __start_annotated_branch_profile;
 277 }
 278
 279 static void *
 280 annotated_branch_stat_next(void *v, int idx)
 281 {
 282         struct ftrace_branch_data *p = v;
 283
 284         ++p;
 285
 286         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 287                 return NULL;
 288
 289         return p;
 290 }
 291
 292 static int annotated_branch_stat_cmp(void *p1, void *p2)
 293 {
 294         struct ftrace_branch_data *a = p1;
 295         struct ftrace_branch_data *b = p2;
 296
 297         long percent_a, percent_b;
 298
 299         percent_a = get_incorrect_percent(a);
 300         percent_b = get_incorrect_percent(b);
 301
 302         if (percent_a < percent_b)
 303                 return -1;
 304         if (percent_a > percent_b)
 305                 return 1;
 306
 307         if (a->incorrect < b->incorrect)
 308                 return -1;
 309         if (a->incorrect > b->incorrect)
 310                 return 1;
 311
 312         /*
 313          * Since the above shows worse (incorrect) cases
 314          * first, we continue that by showing best (correct)
 315          * cases last.
 316          */
 317         if (a->correct > b->correct)
 318                 return -1;
 319         if (a->correct < b->correct)
 320                 return 1;
 321
 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_puts(m, "   miss      hit    % "
 356                     "       Function                "
 357                     "  File              Line\n"
 358                     " ------- ---------  - "
 359                     "       --------                "
 360                     "  ----              ----\n");
 361         return 0;
 362 }
 363
 364 static void *all_branch_stat_start(struct tracer_stat *trace)
 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 */