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 trace_array_cpu *data;
  36         struct ring_buffer_event *event;
  37         struct trace_branch *entry;
  38         struct ring_buffer *buffer;
  39         unsigned long flags;
  40         int cpu, pc;
  41         const char *p;
  42
  43         /*
  44          * I would love to save just the ftrace_likely_data pointer, but
  45          * this code can also be used by modules. Ugly things can happen
  46          * if the module is unloaded, and then we go and read the
  47          * pointer.  This is slower, but much safer.
  48          */
  49
  50         if (unlikely(!tr))
  51                 return;
  52
  53         local_irq_save(flags);
  54         cpu = raw_smp_processor_id();
  55         data = per_cpu_ptr(tr->trace_buffer.data, cpu);
  56         if (atomic_inc_return(&data->disabled) != 1)
  57                 goto out;
  58
  59         pc = preempt_count();
  60         buffer = tr->trace_buffer.buffer;
  61         event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
  62                                           sizeof(*entry), flags, pc);
  63         if (!event)
  64                 goto out;
  65
  66         entry   = ring_buffer_event_data(event);
  67
  68         /* Strip off the path, only save the file */
  69         p = f->file + strlen(f->file);
  70         while (p >= f->file && *p != '/')
  71                 p--;
  72         p++;
  73
  74         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  75         strncpy(entry->file, p, TRACE_FILE_SIZE);
  76         entry->func[TRACE_FUNC_SIZE] = 0;
  77         entry->file[TRACE_FILE_SIZE] = 0;
  78         entry->line = f->line;
  79         entry->correct = val == expect;
  80
  81         if (!call_filter_check_discard(call, entry, buffer, event))
  82                 __buffer_unlock_commit(buffer, event);
  83
  84  out:
  85         atomic_dec(&data->disabled);
  86         local_irq_restore(flags);
  87 }
  88
  89 static inline
  90 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
  91 {
  92         if (!branch_tracing_enabled)
  93                 return;
  94
  95         probe_likely_condition(f, val, expect);
  96 }
  97
  98 int enable_branch_tracing(struct trace_array *tr)
  99 {
 100         mutex_lock(&branch_tracing_mutex);
 101         branch_tracer = tr;
 102         /*
 103          * Must be seen before enabling. The reader is a condition
 104          * where we do not need a matching rmb()
 105          */
 106         smp_wmb();
 107         branch_tracing_enabled++;
 108         mutex_unlock(&branch_tracing_mutex);
 109
 110         return 0;
 111 }
 112
 113 void disable_branch_tracing(void)
 114 {
 115         mutex_lock(&branch_tracing_mutex);
 116
 117         if (!branch_tracing_enabled)
 118                 goto out_unlock;
 119
 120         branch_tracing_enabled--;
 121
 122  out_unlock:
 123         mutex_unlock(&branch_tracing_mutex);
 124 }
 125
 126 static void start_branch_trace(struct trace_array *tr)
 127 {
 128         enable_branch_tracing(tr);
 129 }
 130
 131 static void stop_branch_trace(struct trace_array *tr)
 132 {
 133         disable_branch_tracing();
 134 }
 135
 136 static int branch_trace_init(struct trace_array *tr)
 137 {
 138         start_branch_trace(tr);
 139         return 0;
 140 }
 141
 142 static void branch_trace_reset(struct trace_array *tr)
 143 {
 144         stop_branch_trace(tr);
 145 }
 146
 147 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
 148                                             int flags, struct trace_event *event)
 149 {
 150         struct trace_branch *field;
 151
 152         trace_assign_type(field, iter->ent);
 153
 154         trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
 155                          field->correct ? "  ok  " : " MISS ",
 156                          field->func,
 157                          field->file,
 158                          field->line);
 159
 160         return trace_handle_return(&iter->seq);
 161 }
 162
 163 static void branch_print_header(struct seq_file *s)
 164 {
 165         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 166                     "  FUNC:FILE:LINE\n"
 167                     "#              | |       |          |         |   "
 168                     "    |\n");
 169 }
 170
 171 static struct trace_event_functions trace_branch_funcs = {
 172         .trace          = trace_branch_print,
 173 };
 174
 175 static struct trace_event trace_branch_event = {
 176         .type           = TRACE_BRANCH,
 177         .funcs          = &trace_branch_funcs,
 178 };
 179
 180 static struct tracer branch_trace __read_mostly =
 181 {
 182         .name           = "branch",
 183         .init           = branch_trace_init,
 184         .reset          = branch_trace_reset,
 185 #ifdef CONFIG_FTRACE_SELFTEST
 186         .selftest       = trace_selftest_startup_branch,
 187 #endif /* CONFIG_FTRACE_SELFTEST */
 188         .print_header   = branch_print_header,
 189 };
 190
 191 __init static int init_branch_tracer(void)
 192 {
 193         int ret;
 194
 195         ret = register_ftrace_event(&trace_branch_event);
 196         if (!ret) {
 197                 printk(KERN_WARNING "Warning: could not register "
 198                                     "branch events\n");
 199                 return 1;
 200         }
 201         return register_tracer(&branch_trace);
 202 }
 203 core_initcall(init_branch_tracer);
 204
 205 #else
 206 static inline
 207 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 208 {
 209 }
 210 #endif /* CONFIG_BRANCH_TRACER */
 211
 212 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 213 {
 214         /*
 215          * I would love to have a trace point here instead, but the
 216          * trace point code is so inundated with unlikely and likely
 217          * conditions that the recursive nightmare that exists is too
 218          * much to try to get working. At least for now.
 219          */
 220         trace_likely_condition(f, val, expect);
 221
 222         /* FIXME: Make this atomic! */
 223         if (val == expect)
 224                 f->correct++;
 225         else
 226                 f->incorrect++;
 227 }
 228 EXPORT_SYMBOL(ftrace_likely_update);
 229
 230 extern unsigned long __start_annotated_branch_profile[];
 231 extern unsigned long __stop_annotated_branch_profile[];
 232
 233 static int annotated_branch_stat_headers(struct seq_file *m)
 234 {
 235         seq_puts(m, " correct incorrect  % "
 236                     "       Function                "
 237                     "  File              Line\n"
 238                     " ------- ---------  - "
 239                     "       --------                "
 240                     "  ----              ----\n");
 241         return 0;
 242 }
 243
 244 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 245 {
 246         long percent;
 247
 248         if (p->correct) {
 249                 percent = p->incorrect * 100;
 250                 percent /= p->correct + p->incorrect;
 251         } else
 252                 percent = p->incorrect ? 100 : -1;
 253
 254         return percent;
 255 }
 256
 257 static int branch_stat_show(struct seq_file *m, void *v)
 258 {
 259         struct ftrace_branch_data *p = v;
 260         const char *f;
 261         long percent;
 262
 263         /* Only print the file, not the path */
 264         f = p->file + strlen(p->file);
 265         while (f >= p->file && *f != '/')
 266                 f--;
 267         f++;
 268
 269         /*
 270          * The miss is overlayed on correct, and hit on incorrect.
 271          */
 272         percent = get_incorrect_percent(p);
 273
 274         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 275         if (percent < 0)
 276                 seq_puts(m, "  X ");
 277         else
 278                 seq_printf(m, "%3ld ", percent);
 279         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 280         return 0;
 281 }
 282
 283 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 284 {
 285         return __start_annotated_branch_profile;
 286 }
 287
 288 static void *
 289 annotated_branch_stat_next(void *v, int idx)
 290 {
 291         struct ftrace_branch_data *p = v;
 292
 293         ++p;
 294
 295         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 296                 return NULL;
 297
 298         return p;
 299 }
 300
 301 static int annotated_branch_stat_cmp(void *p1, void *p2)
 302 {
 303         struct ftrace_branch_data *a = p1;
 304         struct ftrace_branch_data *b = p2;
 305
 306         long percent_a, percent_b;
 307
 308         percent_a = get_incorrect_percent(a);
 309         percent_b = get_incorrect_percent(b);
 310
 311         if (percent_a < percent_b)
 312                 return -1;
 313         if (percent_a > percent_b)
 314                 return 1;
 315
 316         if (a->incorrect < b->incorrect)
 317                 return -1;
 318         if (a->incorrect > b->incorrect)
 319                 return 1;
 320
 321         /*
 322          * Since the above shows worse (incorrect) cases
 323          * first, we continue that by showing best (correct)
 324          * cases last.
 325          */
 326         if (a->correct > b->correct)
 327                 return -1;
 328         if (a->correct < b->correct)
 329                 return 1;
 330
 331         return 0;
 332 }
 333
 334 static struct tracer_stat annotated_branch_stats = {
 335         .name = "branch_annotated",
 336         .stat_start = annotated_branch_stat_start,
 337         .stat_next = annotated_branch_stat_next,
 338         .stat_cmp = annotated_branch_stat_cmp,
 339         .stat_headers = annotated_branch_stat_headers,
 340         .stat_show = branch_stat_show
 341 };
 342
 343 __init static int init_annotated_branch_stats(void)
 344 {
 345         int ret;
 346
 347         ret = register_stat_tracer(&annotated_branch_stats);
 348         if (!ret) {
 349                 printk(KERN_WARNING "Warning: could not register "
 350                                     "annotated branches stats\n");
 351                 return 1;
 352         }
 353         return 0;
 354 }
 355 fs_initcall(init_annotated_branch_stats);
 356
 357 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 358
 359 extern unsigned long __start_branch_profile[];
 360 extern unsigned long __stop_branch_profile[];
 361
 362 static int all_branch_stat_headers(struct seq_file *m)
 363 {
 364         seq_puts(m, "   miss      hit    % "
 365                     "       Function                "
 366                     "  File              Line\n"
 367                     " ------- ---------  - "
 368                     "       --------                "
 369                     "  ----              ----\n");
 370         return 0;
 371 }
 372
 373 static void *all_branch_stat_start(struct tracer_stat *trace)
 374 {
 375         return __start_branch_profile;
 376 }
 377
 378 static void *
 379 all_branch_stat_next(void *v, int idx)
 380 {
 381         struct ftrace_branch_data *p = v;
 382
 383         ++p;
 384
 385         if ((void *)p >= (void *)__stop_branch_profile)
 386                 return NULL;
 387
 388         return p;
 389 }
 390
 391 static struct tracer_stat all_branch_stats = {
 392         .name = "branch_all",
 393         .stat_start = all_branch_stat_start,
 394         .stat_next = all_branch_stat_next,
 395         .stat_headers = all_branch_stat_headers,
 396         .stat_show = branch_stat_show
 397 };
 398
 399 __init static int all_annotated_branch_stats(void)
 400 {
 401         int ret;
 402
 403         ret = register_stat_tracer(&all_branch_stats);
 404         if (!ret) {
 405                 printk(KERN_WARNING "Warning: could not register "
 406                                     "all branches stats\n");
 407                 return 1;
 408         }
 409         return 0;
 410 }
 411 fs_initcall(all_annotated_branch_stats);
 412 #endif /* CONFIG_PROFILE_ALL_BRANCHES */