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