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,
 204                           int expect, int is_constant)
 205 {
 206         /* A constant is always correct */
 207         if (is_constant)
 208                 val = expect;
 209         /*
 210          * I would love to have a trace point here instead, but the
 211          * trace point code is so inundated with unlikely and likely
 212          * conditions that the recursive nightmare that exists is too
 213          * much to try to get working. At least for now.
 214          */
 215         trace_likely_condition(f, val, expect);
 216
 217         /* FIXME: Make this atomic! */
 218         if (val == expect)
 219                 f->correct++;
 220         else
 221                 f->incorrect++;
 222 }
 223 EXPORT_SYMBOL(ftrace_likely_update);
 224
 225 extern unsigned long __start_annotated_branch_profile[];
 226 extern unsigned long __stop_annotated_branch_profile[];
 227
 228 static int annotated_branch_stat_headers(struct seq_file *m)
 229 {
 230         seq_puts(m, " correct incorrect  % "
 231                     "       Function                "
 232                     "  File              Line\n"
 233                     " ------- ---------  - "
 234                     "       --------                "
 235                     "  ----              ----\n");
 236         return 0;
 237 }
 238
 239 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 240 {
 241         long percent;
 242
 243         if (p->correct) {
 244                 percent = p->incorrect * 100;
 245                 percent /= p->correct + p->incorrect;
 246         } else
 247                 percent = p->incorrect ? 100 : -1;
 248
 249         return percent;
 250 }
 251
 252 static int branch_stat_show(struct seq_file *m, void *v)
 253 {
 254         struct ftrace_branch_data *p = v;
 255         const char *f;
 256         long percent;
 257
 258         /* Only print the file, not the path */
 259         f = p->file + strlen(p->file);
 260         while (f >= p->file && *f != '/')
 261                 f--;
 262         f++;
 263
 264         /*
 265          * The miss is overlayed on correct, and hit on incorrect.
 266          */
 267         percent = get_incorrect_percent(p);
 268
 269         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 270         if (percent < 0)
 271                 seq_puts(m, "  X ");
 272         else
 273                 seq_printf(m, "%3ld ", percent);
 274         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 275         return 0;
 276 }
 277
 278 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 279 {
 280         return __start_annotated_branch_profile;
 281 }
 282
 283 static void *
 284 annotated_branch_stat_next(void *v, int idx)
 285 {
 286         struct ftrace_branch_data *p = v;
 287
 288         ++p;
 289
 290         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 291                 return NULL;
 292
 293         return p;
 294 }
 295
 296 static int annotated_branch_stat_cmp(void *p1, void *p2)
 297 {
 298         struct ftrace_branch_data *a = p1;
 299         struct ftrace_branch_data *b = p2;
 300
 301         long percent_a, percent_b;
 302
 303         percent_a = get_incorrect_percent(a);
 304         percent_b = get_incorrect_percent(b);
 305
 306         if (percent_a < percent_b)
 307                 return -1;
 308         if (percent_a > percent_b)
 309                 return 1;
 310
 311         if (a->incorrect < b->incorrect)
 312                 return -1;
 313         if (a->incorrect > b->incorrect)
 314                 return 1;
 315
 316         /*
 317          * Since the above shows worse (incorrect) cases
 318          * first, we continue that by showing best (correct)
 319          * cases last.
 320          */
 321         if (a->correct > b->correct)
 322                 return -1;
 323         if (a->correct < b->correct)
 324                 return 1;
 325
 326         return 0;
 327 }
 328
 329 static struct tracer_stat annotated_branch_stats = {
 330         .name = "branch_annotated",
 331         .stat_start = annotated_branch_stat_start,
 332         .stat_next = annotated_branch_stat_next,
 333         .stat_cmp = annotated_branch_stat_cmp,
 334         .stat_headers = annotated_branch_stat_headers,
 335         .stat_show = branch_stat_show
 336 };
 337
 338 __init static int init_annotated_branch_stats(void)
 339 {
 340         int ret;
 341
 342         ret = register_stat_tracer(&annotated_branch_stats);
 343         if (!ret) {
 344                 printk(KERN_WARNING "Warning: could not register "
 345                                     "annotated branches stats\n");
 346                 return 1;
 347         }
 348         return 0;
 349 }
 350 fs_initcall(init_annotated_branch_stats);
 351
 352 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 353
 354 extern unsigned long __start_branch_profile[];
 355 extern unsigned long __stop_branch_profile[];
 356
 357 static int all_branch_stat_headers(struct seq_file *m)
 358 {
 359         seq_puts(m, "   miss      hit    % "
 360                     "       Function                "
 361                     "  File              Line\n"
 362                     " ------- ---------  - "
 363                     "       --------                "
 364                     "  ----              ----\n");
 365         return 0;
 366 }
 367
 368 static void *all_branch_stat_start(struct tracer_stat *trace)
 369 {
 370         return __start_branch_profile;
 371 }
 372
 373 static void *
 374 all_branch_stat_next(void *v, int idx)
 375 {
 376         struct ftrace_branch_data *p = v;
 377
 378         ++p;
 379
 380         if ((void *)p >= (void *)__stop_branch_profile)
 381                 return NULL;
 382
 383         return p;
 384 }
 385
 386 static struct tracer_stat all_branch_stats = {
 387         .name = "branch_all",
 388         .stat_start = all_branch_stat_start,
 389         .stat_next = all_branch_stat_next,
 390         .stat_headers = all_branch_stat_headers,
 391         .stat_show = branch_stat_show
 392 };
 393
 394 __init static int all_annotated_branch_stats(void)
 395 {
 396         int ret;
 397
 398         ret = register_stat_tracer(&all_branch_stats);
 399         if (!ret) {
 400                 printk(KERN_WARNING "Warning: could not register "
 401                                     "all branches stats\n");
 402                 return 1;
 403         }
 404         return 0;
 405 }
 406 fs_initcall(all_annotated_branch_stats);
 407 #endif /* CONFIG_PROFILE_ALL_BRANCHES */