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