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 (!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         if (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                 return TRACE_TYPE_PARTIAL_LINE;
 160
 161         return TRACE_TYPE_HANDLED;
 162 }
 163
 164 static void branch_print_header(struct seq_file *s)
 165 {
 166         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
 167                 "  FUNC:FILE:LINE\n");
 168         seq_puts(s, "#              | |       |          |         |   "
 169                 "    |\n");
 170 }
 171
 172 static struct trace_event_functions trace_branch_funcs = {
 173         .trace          = trace_branch_print,
 174 };
 175
 176 static struct trace_event trace_branch_event = {
 177         .type           = TRACE_BRANCH,
 178         .funcs          = &trace_branch_funcs,
 179 };
 180
 181 static struct tracer branch_trace __read_mostly =
 182 {
 183         .name           = "branch",
 184         .init           = branch_trace_init,
 185         .reset          = branch_trace_reset,
 186 #ifdef CONFIG_FTRACE_SELFTEST
 187         .selftest       = trace_selftest_startup_branch,
 188 #endif /* CONFIG_FTRACE_SELFTEST */
 189         .print_header   = branch_print_header,
 190 };
 191
 192 __init static int init_branch_tracer(void)
 193 {
 194         int ret;
 195
 196         ret = register_ftrace_event(&trace_branch_event);
 197         if (!ret) {
 198                 printk(KERN_WARNING "Warning: could not register "
 199                                     "branch events\n");
 200                 return 1;
 201         }
 202         return register_tracer(&branch_trace);
 203 }
 204 core_initcall(init_branch_tracer);
 205
 206 #else
 207 static inline
 208 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 209 {
 210 }
 211 #endif /* CONFIG_BRANCH_TRACER */
 212
 213 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
 214 {
 215         /*
 216          * I would love to have a trace point here instead, but the
 217          * trace point code is so inundated with unlikely and likely
 218          * conditions that the recursive nightmare that exists is too
 219          * much to try to get working. At least for now.
 220          */
 221         trace_likely_condition(f, val, expect);
 222
 223         /* FIXME: Make this atomic! */
 224         if (val == expect)
 225                 f->correct++;
 226         else
 227                 f->incorrect++;
 228 }
 229 EXPORT_SYMBOL(ftrace_likely_update);
 230
 231 extern unsigned long __start_annotated_branch_profile[];
 232 extern unsigned long __stop_annotated_branch_profile[];
 233
 234 static int annotated_branch_stat_headers(struct seq_file *m)
 235 {
 236         seq_printf(m, " correct incorrect  %% ");
 237         seq_printf(m, "       Function                "
 238                               "  File              Line\n"
 239                               " ------- ---------  - "
 240                               "       --------                "
 241                               "  ----              ----\n");
 242         return 0;
 243 }
 244
 245 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 246 {
 247         long percent;
 248
 249         if (p->correct) {
 250                 percent = p->incorrect * 100;
 251                 percent /= p->correct + p->incorrect;
 252         } else
 253                 percent = p->incorrect ? 100 : -1;
 254
 255         return percent;
 256 }
 257
 258 static int branch_stat_show(struct seq_file *m, void *v)
 259 {
 260         struct ftrace_branch_data *p = v;
 261         const char *f;
 262         long percent;
 263
 264         /* Only print the file, not the path */
 265         f = p->file + strlen(p->file);
 266         while (f >= p->file && *f != '/')
 267                 f--;
 268         f++;
 269
 270         /*
 271          * The miss is overlayed on correct, and hit on incorrect.
 272          */
 273         percent = get_incorrect_percent(p);
 274
 275         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 276         if (percent < 0)
 277                 seq_printf(m, "  X ");
 278         else
 279                 seq_printf(m, "%3ld ", percent);
 280         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 281         return 0;
 282 }
 283
 284 static void *annotated_branch_stat_start(struct tracer_stat *trace)
 285 {
 286         return __start_annotated_branch_profile;
 287 }
 288
 289 static void *
 290 annotated_branch_stat_next(void *v, int idx)
 291 {
 292         struct ftrace_branch_data *p = v;
 293
 294         ++p;
 295
 296         if ((void *)p >= (void *)__stop_annotated_branch_profile)
 297                 return NULL;
 298
 299         return p;
 300 }
 301
 302 static int annotated_branch_stat_cmp(void *p1, void *p2)
 303 {
 304         struct ftrace_branch_data *a = p1;
 305         struct ftrace_branch_data *b = p2;
 306
 307         long percent_a, percent_b;
 308
 309         percent_a = get_incorrect_percent(a);
 310         percent_b = get_incorrect_percent(b);
 311
 312         if (percent_a < percent_b)
 313                 return -1;
 314         if (percent_a > percent_b)
 315                 return 1;
 316
 317         if (a->incorrect < b->incorrect)
 318                 return -1;
 319         if (a->incorrect > b->incorrect)
 320                 return 1;
 321
 322         /*
 323          * Since the above shows worse (incorrect) cases
 324          * first, we continue that by showing best (correct)
 325          * cases last.
 326          */
 327         if (a->correct > b->correct)
 328                 return -1;
 329         if (a->correct < b->correct)
 330                 return 1;
 331
 332         return 0;
 333 }
 334
 335 static struct tracer_stat annotated_branch_stats = {
 336         .name = "branch_annotated",
 337         .stat_start = annotated_branch_stat_start,
 338         .stat_next = annotated_branch_stat_next,
 339         .stat_cmp = annotated_branch_stat_cmp,
 340         .stat_headers = annotated_branch_stat_headers,
 341         .stat_show = branch_stat_show
 342 };
 343
 344 __init static int init_annotated_branch_stats(void)
 345 {
 346         int ret;
 347
 348         ret = register_stat_tracer(&annotated_branch_stats);
 349         if (!ret) {
 350                 printk(KERN_WARNING "Warning: could not register "
 351                                     "annotated branches stats\n");
 352                 return 1;
 353         }
 354         return 0;
 355 }
 356 fs_initcall(init_annotated_branch_stats);
 357
 358 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 359
 360 extern unsigned long __start_branch_profile[];
 361 extern unsigned long __stop_branch_profile[];
 362
 363 static int all_branch_stat_headers(struct seq_file *m)
 364 {
 365         seq_printf(m, "   miss      hit    %% ");
 366         seq_printf(m, "       Function                "
 367                               "  File              Line\n"
 368                               " ------- ---------  - "
 369                               "       --------                "
 370                               "  ----              ----\n");
 371         return 0;
 372 }
 373
 374 static void *all_branch_stat_start(struct tracer_stat *trace)
 375 {
 376         return __start_branch_profile;
 377 }
 378
 379 static void *
 380 all_branch_stat_next(void *v, int idx)
 381 {
 382         struct ftrace_branch_data *p = v;
 383
 384         ++p;
 385
 386         if ((void *)p >= (void *)__stop_branch_profile)
 387                 return NULL;
 388
 389         return p;
 390 }
 391
 392 static struct tracer_stat all_branch_stats = {
 393         .name = "branch_all",
 394         .stat_start = all_branch_stat_start,
 395         .stat_next = all_branch_stat_next,
 396         .stat_headers = all_branch_stat_headers,
 397         .stat_show = branch_stat_show
 398 };
 399
 400 __init static int all_annotated_branch_stats(void)
 401 {
 402         int ret;
 403
 404         ret = register_stat_tracer(&all_branch_stats);
 405         if (!ret) {
 406                 printk(KERN_WARNING "Warning: could not register "
 407                                     "all branches stats\n");
 408                 return 1;
 409         }
 410         return 0;
 411 }
 412 fs_initcall(all_annotated_branch_stats);
 413 #endif /* CONFIG_PROFILE_ALL_BRANCHES */