kernel/profile.c

   1 /*
   2  *  linux/kernel/profile.c
   3  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   4  *  with configurable resolution, support for restricting the cpus on
   5  *  which profiling is done, and switching between cpu time and
   6  *  schedule() calls via kernel command line parameters passed at boot.
   7  *
   8  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
   9  *      Red Hat, July 2004
  10  *  Consolidation of architecture support code for profiling,
  11  *      William Irwin, Oracle, July 2004
  12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13  *      to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/profile.h>
  18 #include <linux/bootmem.h>
  19 #include <linux/notifier.h>
  20 #include <linux/mm.h>
  21 #include <linux/cpumask.h>
  22 #include <linux/cpu.h>
  23 #include <linux/highmem.h>
  24 #include <linux/mutex.h>
  25 #include <linux/slab.h>
  26 #include <linux/vmalloc.h>
  27 #include <asm/sections.h>
  28 #include <asm/irq_regs.h>
  29 #include <asm/ptrace.h>
  30
  31 struct profile_hit {
  32         u32 pc, hits;
  33 };
  34 #define PROFILE_GRPSHIFT        3
  35 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  36 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  37 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  38
  39 /* Oprofile timer tick hook */
  40 static int (*timer_hook)(struct pt_regs *) __read_mostly;
  41
  42 static atomic_t *prof_buffer;
  43 static unsigned long prof_len, prof_shift;
  44
  45 int prof_on __read_mostly;
  46 EXPORT_SYMBOL_GPL(prof_on);
  47
  48 static cpumask_var_t prof_cpu_mask;
  49 #ifdef CONFIG_SMP
  50 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  51 static DEFINE_PER_CPU(int, cpu_profile_flip);
  52 static DEFINE_MUTEX(profile_flip_mutex);
  53 #endif /* CONFIG_SMP */
  54
  55 int profile_setup(char *str)
  56 {
  57         static char schedstr[] = "schedule";
  58         static char sleepstr[] = "sleep";
  59         static char kvmstr[] = "kvm";
  60         int par;
  61
  62         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  63 #ifdef CONFIG_SCHEDSTATS
  64                 prof_on = SLEEP_PROFILING;
  65                 if (str[strlen(sleepstr)] == ',')
  66                         str += strlen(sleepstr) + 1;
  67                 if (get_option(&str, &par))
  68                         prof_shift = par;
  69                 printk(KERN_INFO
  70                         "kernel sleep profiling enabled (shift: %ld)\n",
  71                         prof_shift);
  72 #else
  73                 printk(KERN_WARNING
  74                         "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  75 #endif /* CONFIG_SCHEDSTATS */
  76         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  77                 prof_on = SCHED_PROFILING;
  78                 if (str[strlen(schedstr)] == ',')
  79                         str += strlen(schedstr) + 1;
  80                 if (get_option(&str, &par))
  81                         prof_shift = par;
  82                 printk(KERN_INFO
  83                         "kernel schedule profiling enabled (shift: %ld)\n",
  84                         prof_shift);
  85         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  86                 prof_on = KVM_PROFILING;
  87                 if (str[strlen(kvmstr)] == ',')
  88                         str += strlen(kvmstr) + 1;
  89                 if (get_option(&str, &par))
  90                         prof_shift = par;
  91                 printk(KERN_INFO
  92                         "kernel KVM profiling enabled (shift: %ld)\n",
  93                         prof_shift);
  94         } else if (get_option(&str, &par)) {
  95                 prof_shift = par;
  96                 prof_on = CPU_PROFILING;
  97                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  98                         prof_shift);
  99         }
 100         return 1;
 101 }
 102 __setup("profile=", profile_setup);
 103
 104
 105 int __ref profile_init(void)
 106 {
 107         int buffer_bytes;
 108         if (!prof_on)
 109                 return 0;
 110
 111         /* only text is profiled */
 112         prof_len = (_etext - _stext) >> prof_shift;
 113         buffer_bytes = prof_len*sizeof(atomic_t);
 114         if (!slab_is_available()) {
 115                 prof_buffer = alloc_bootmem(buffer_bytes);
 116                 alloc_bootmem_cpumask_var(&prof_cpu_mask);
 117                 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 118                 return 0;
 119         }
 120
 121         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 122                 return -ENOMEM;
 123
 124         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 125
 126         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
 127         if (prof_buffer)
 128                 return 0;
 129
 130         prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO);
 131         if (prof_buffer)
 132                 return 0;
 133
 134         prof_buffer = vmalloc(buffer_bytes);
 135         if (prof_buffer)
 136                 return 0;
 137
 138         free_cpumask_var(prof_cpu_mask);
 139         return -ENOMEM;
 140 }
 141
 142 /* Profile event notifications */
 143
 144 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 145 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 146 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 147
 148 void profile_task_exit(struct task_struct *task)
 149 {
 150         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 151 }
 152
 153 int profile_handoff_task(struct task_struct *task)
 154 {
 155         int ret;
 156         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 157         return (ret == NOTIFY_OK) ? 1 : 0;
 158 }
 159
 160 void profile_munmap(unsigned long addr)
 161 {
 162         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 163 }
 164
 165 int task_handoff_register(struct notifier_block *n)
 166 {
 167         return atomic_notifier_chain_register(&task_free_notifier, n);
 168 }
 169 EXPORT_SYMBOL_GPL(task_handoff_register);
 170
 171 int task_handoff_unregister(struct notifier_block *n)
 172 {
 173         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 174 }
 175 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 176
 177 int profile_event_register(enum profile_type type, struct notifier_block *n)
 178 {
 179         int err = -EINVAL;
 180
 181         switch (type) {
 182         case PROFILE_TASK_EXIT:
 183                 err = blocking_notifier_chain_register(
 184                                 &task_exit_notifier, n);
 185                 break;
 186         case PROFILE_MUNMAP:
 187                 err = blocking_notifier_chain_register(
 188                                 &munmap_notifier, n);
 189                 break;
 190         }
 191
 192         return err;
 193 }
 194 EXPORT_SYMBOL_GPL(profile_event_register);
 195
 196 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 197 {
 198         int err = -EINVAL;
 199
 200         switch (type) {
 201         case PROFILE_TASK_EXIT:
 202                 err = blocking_notifier_chain_unregister(
 203                                 &task_exit_notifier, n);
 204                 break;
 205         case PROFILE_MUNMAP:
 206                 err = blocking_notifier_chain_unregister(
 207                                 &munmap_notifier, n);
 208                 break;
 209         }
 210
 211         return err;
 212 }
 213 EXPORT_SYMBOL_GPL(profile_event_unregister);
 214
 215 int register_timer_hook(int (*hook)(struct pt_regs *))
 216 {
 217         if (timer_hook)
 218                 return -EBUSY;
 219         timer_hook = hook;
 220         return 0;
 221 }
 222 EXPORT_SYMBOL_GPL(register_timer_hook);
 223
 224 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 225 {
 226         WARN_ON(hook != timer_hook);
 227         timer_hook = NULL;
 228         /* make sure all CPUs see the NULL hook */
 229         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 230 }
 231 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 232
 233
 234 #ifdef CONFIG_SMP
 235 /*
 236  * Each cpu has a pair of open-addressed hashtables for pending
 237  * profile hits. read_profile() IPI's all cpus to request them
 238  * to flip buffers and flushes their contents to prof_buffer itself.
 239  * Flip requests are serialized by the profile_flip_mutex. The sole
 240  * use of having a second hashtable is for avoiding cacheline
 241  * contention that would otherwise happen during flushes of pending
 242  * profile hits required for the accuracy of reported profile hits
 243  * and so resurrect the interrupt livelock issue.
 244  *
 245  * The open-addressed hashtables are indexed by profile buffer slot
 246  * and hold the number of pending hits to that profile buffer slot on
 247  * a cpu in an entry. When the hashtable overflows, all pending hits
 248  * are accounted to their corresponding profile buffer slots with
 249  * atomic_add() and the hashtable emptied. As numerous pending hits
 250  * may be accounted to a profile buffer slot in a hashtable entry,
 251  * this amortizes a number of atomic profile buffer increments likely
 252  * to be far larger than the number of entries in the hashtable,
 253  * particularly given that the number of distinct profile buffer
 254  * positions to which hits are accounted during short intervals (e.g.
 255  * several seconds) is usually very small. Exclusion from buffer
 256  * flipping is provided by interrupt disablement (note that for
 257  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 258  * process context).
 259  * The hash function is meant to be lightweight as opposed to strong,
 260  * and was vaguely inspired by ppc64 firmware-supported inverted
 261  * pagetable hash functions, but uses a full hashtable full of finite
 262  * collision chains, not just pairs of them.
 263  *
 264  * -- wli
 265  */
 266 #ifdef CONFIG_PROC_FS
 267 static void __profile_flip_buffers(void *unused)
 268 {
 269         int cpu = smp_processor_id();
 270
 271         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 272 }
 273
 274 static void profile_flip_buffers(void)
 275 {
 276         int i, j, cpu;
 277
 278         mutex_lock(&profile_flip_mutex);
 279         j = per_cpu(cpu_profile_flip, get_cpu());
 280         put_cpu();
 281         on_each_cpu(__profile_flip_buffers, NULL, 1);
 282         for_each_online_cpu(cpu) {
 283                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 284                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 285                         if (!hits[i].hits) {
 286                                 if (hits[i].pc)
 287                                         hits[i].pc = 0;
 288                                 continue;
 289                         }
 290                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 291                         hits[i].hits = hits[i].pc = 0;
 292                 }
 293         }
 294         mutex_unlock(&profile_flip_mutex);
 295 }
 296
 297 static void profile_discard_flip_buffers(void)
 298 {
 299         int i, cpu;
 300
 301         mutex_lock(&profile_flip_mutex);
 302         i = per_cpu(cpu_profile_flip, get_cpu());
 303         put_cpu();
 304         on_each_cpu(__profile_flip_buffers, NULL, 1);
 305         for_each_online_cpu(cpu) {
 306                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 307                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 308         }
 309         mutex_unlock(&profile_flip_mutex);
 310 }
 311
 312 static int __cpuinit profile_cpu_callback(struct notifier_block *info,
 313                                         unsigned long action, void *__cpu)
 314 {
 315         int node, cpu = (unsigned long)__cpu;
 316         struct page *page;
 317
 318         switch (action) {
 319         case CPU_UP_PREPARE:
 320         case CPU_UP_PREPARE_FROZEN:
 321                 node = cpu_to_node(cpu);
 322                 per_cpu(cpu_profile_flip, cpu) = 0;
 323                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 324                         page = alloc_pages_node(node,
 325                                         GFP_KERNEL | __GFP_ZERO,
 326                                         0);
 327                         if (!page)
 328                                 return NOTIFY_BAD;
 329                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 330                 }
 331                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 332                         page = alloc_pages_node(node,
 333                                         GFP_KERNEL | __GFP_ZERO,
 334                                         0);
 335                         if (!page)
 336                                 goto out_free;
 337                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 338                 }
 339                 break;
 340 out_free:
 341                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 342                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 343                 __free_page(page);
 344                 return NOTIFY_BAD;
 345         case CPU_ONLINE:
 346         case CPU_ONLINE_FROZEN:
 347                 if (prof_cpu_mask != NULL)
 348                         cpumask_set_cpu(cpu, prof_cpu_mask);
 349                 break;
 350         case CPU_UP_CANCELED:
 351         case CPU_UP_CANCELED_FROZEN:
 352         case CPU_DEAD:
 353         case CPU_DEAD_FROZEN:
 354                 if (prof_cpu_mask != NULL)
 355                         cpumask_clear_cpu(cpu, prof_cpu_mask);
 356                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 357                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 358                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 359                         __free_page(page);
 360                 }
 361                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 362                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 363                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 364                         __free_page(page);
 365                 }
 366                 break;
 367         }
 368         return NOTIFY_OK;
 369 }
 370 #endif /* CONFIG_PROC_FS */
 371
 372 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 373 {
 374         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 375         int i, j, cpu;
 376         struct profile_hit *hits;
 377
 378         if (prof_on != type || !prof_buffer)
 379                 return;
 380         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 381         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 382         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 383         cpu = get_cpu();
 384         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 385         if (!hits) {
 386                 put_cpu();
 387                 return;
 388         }
 389         /*
 390          * We buffer the global profiler buffer into a per-CPU
 391          * queue and thus reduce the number of global (and possibly
 392          * NUMA-alien) accesses. The write-queue is self-coalescing:
 393          */
 394         local_irq_save(flags);
 395         do {
 396                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 397                         if (hits[i + j].pc == pc) {
 398                                 hits[i + j].hits += nr_hits;
 399                                 goto out;
 400                         } else if (!hits[i + j].hits) {
 401                                 hits[i + j].pc = pc;
 402                                 hits[i + j].hits = nr_hits;
 403                                 goto out;
 404                         }
 405                 }
 406                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 407         } while (i != primary);
 408
 409         /*
 410          * Add the current hit(s) and flush the write-queue out
 411          * to the global buffer:
 412          */
 413         atomic_add(nr_hits, &prof_buffer[pc]);
 414         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 415                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 416                 hits[i].pc = hits[i].hits = 0;
 417         }
 418 out:
 419         local_irq_restore(flags);
 420         put_cpu();
 421 }
 422
 423
 424 #else /* !CONFIG_SMP */
 425 #define profile_flip_buffers()          do { } while (0)
 426 #define profile_discard_flip_buffers()  do { } while (0)
 427 #define profile_cpu_callback            NULL
 428
 429 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 430 {
 431         unsigned long pc;
 432
 433         if (prof_on != type || !prof_buffer)
 434                 return;
 435         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 436         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 437 }
 438 #endif /* !CONFIG_SMP */
 439 EXPORT_SYMBOL_GPL(profile_hits);
 440
 441 void profile_tick(int type)
 442 {
 443         struct pt_regs *regs = get_irq_regs();
 444
 445         if (type == CPU_PROFILING && timer_hook)
 446                 timer_hook(regs);
 447         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 448             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 449                 profile_hit(type, (void *)profile_pc(regs));
 450 }
 451
 452 #ifdef CONFIG_PROC_FS
 453 #include <linux/proc_fs.h>
 454 #include <asm/uaccess.h>
 455
 456 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
 457                         int count, int *eof, void *data)
 458 {
 459         int len = cpumask_scnprintf(page, count, data);
 460         if (count - len < 2)
 461                 return -EINVAL;
 462         len += sprintf(page + len, "\n");
 463         return len;
 464 }
 465
 466 static int prof_cpu_mask_write_proc(struct file *file,
 467         const char __user *buffer,  unsigned long count, void *data)
 468 {
 469         struct cpumask *mask = data;
 470         unsigned long full_count = count, err;
 471         cpumask_var_t new_value;
 472
 473         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 474                 return -ENOMEM;
 475
 476         err = cpumask_parse_user(buffer, count, new_value);
 477         if (!err) {
 478                 cpumask_copy(mask, new_value);
 479                 err = full_count;
 480         }
 481         free_cpumask_var(new_value);
 482         return err;
 483 }
 484
 485 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 486 {
 487         struct proc_dir_entry *entry;
 488
 489         /* create /proc/irq/prof_cpu_mask */
 490         entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
 491         if (!entry)
 492                 return;
 493         entry->data = prof_cpu_mask;
 494         entry->read_proc = prof_cpu_mask_read_proc;
 495         entry->write_proc = prof_cpu_mask_write_proc;
 496 }
 497
 498 /*
 499  * This function accesses profiling information. The returned data is
 500  * binary: the sampling step and the actual contents of the profile
 501  * buffer. Use of the program readprofile is recommended in order to
 502  * get meaningful info out of these data.
 503  */
 504 static ssize_t
 505 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 506 {
 507         unsigned long p = *ppos;
 508         ssize_t read;
 509         char *pnt;
 510         unsigned int sample_step = 1 << prof_shift;
 511
 512         profile_flip_buffers();
 513         if (p >= (prof_len+1)*sizeof(unsigned int))
 514                 return 0;
 515         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 516                 count = (prof_len+1)*sizeof(unsigned int) - p;
 517         read = 0;
 518
 519         while (p < sizeof(unsigned int) && count > 0) {
 520                 if (put_user(*((char *)(&sample_step)+p), buf))
 521                         return -EFAULT;
 522                 buf++; p++; count--; read++;
 523         }
 524         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 525         if (copy_to_user(buf, (void *)pnt, count))
 526                 return -EFAULT;
 527         read += count;
 528         *ppos += read;
 529         return read;
 530 }
 531
 532 /*
 533  * Writing to /proc/profile resets the counters
 534  *
 535  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 536  * interrupt frequency, on architectures that support this.
 537  */
 538 static ssize_t write_profile(struct file *file, const char __user *buf,
 539                              size_t count, loff_t *ppos)
 540 {
 541 #ifdef CONFIG_SMP
 542         extern int setup_profiling_timer(unsigned int multiplier);
 543
 544         if (count == sizeof(int)) {
 545                 unsigned int multiplier;
 546
 547                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 548                         return -EFAULT;
 549
 550                 if (setup_profiling_timer(multiplier))
 551                         return -EINVAL;
 552         }
 553 #endif
 554         profile_discard_flip_buffers();
 555         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 556         return count;
 557 }
 558
 559 static const struct file_operations proc_profile_operations = {
 560         .read           = read_profile,
 561         .write          = write_profile,
 562 };
 563
 564 #ifdef CONFIG_SMP
 565 static void profile_nop(void *unused)
 566 {
 567 }
 568
 569 static int create_hash_tables(void)
 570 {
 571         int cpu;
 572
 573         for_each_online_cpu(cpu) {
 574                 int node = cpu_to_node(cpu);
 575                 struct page *page;
 576
 577                 page = alloc_pages_node(node,
 578                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 579                                 0);
 580                 if (!page)
 581                         goto out_cleanup;
 582                 per_cpu(cpu_profile_hits, cpu)[1]
 583                                 = (struct profile_hit *)page_address(page);
 584                 page = alloc_pages_node(node,
 585                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 586                                 0);
 587                 if (!page)
 588                         goto out_cleanup;
 589                 per_cpu(cpu_profile_hits, cpu)[0]
 590                                 = (struct profile_hit *)page_address(page);
 591         }
 592         return 0;
 593 out_cleanup:
 594         prof_on = 0;
 595         smp_mb();
 596         on_each_cpu(profile_nop, NULL, 1);
 597         for_each_online_cpu(cpu) {
 598                 struct page *page;
 599
 600                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 601                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 602                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 603                         __free_page(page);
 604                 }
 605                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 606                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 607                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 608                         __free_page(page);
 609                 }
 610         }
 611         return -1;
 612 }
 613 #else
 614 #define create_hash_tables()                    ({ 0; })
 615 #endif
 616
 617 int create_proc_profile(void)
 618 {
 619         struct proc_dir_entry *entry;
 620
 621         if (!prof_on)
 622                 return 0;
 623         if (create_hash_tables())
 624                 return -ENOMEM;
 625         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 626                             NULL, &proc_profile_operations);
 627         if (!entry)
 628                 return 0;
 629         entry->size = (1+prof_len) * sizeof(atomic_t);
 630         hotcpu_notifier(profile_cpu_callback, 0);
 631         return 0;
 632 }
 633 module_init(create_proc_profile);
 634 #endif /* CONFIG_PROC_FS */