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/config.h>
  17 #include <linux/module.h>
  18 #include <linux/profile.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/notifier.h>
  21 #include <linux/mm.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/cpu.h>
  24 #include <linux/profile.h>
  25 #include <linux/highmem.h>
  26 #include <asm/sections.h>
  27 #include <asm/semaphore.h>
  28
  29 struct profile_hit {
  30         u32 pc, hits;
  31 };
  32 #define PROFILE_GRPSHIFT        3
  33 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  34 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  35 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  36
  37 /* Oprofile timer tick hook */
  38 int (*timer_hook)(struct pt_regs *);
  39
  40 static atomic_t *prof_buffer;
  41 static unsigned long prof_len, prof_shift;
  42 static int prof_on;
  43 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
  44 #ifdef CONFIG_SMP
  45 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  46 static DEFINE_PER_CPU(int, cpu_profile_flip);
  47 static DECLARE_MUTEX(profile_flip_mutex);
  48 #endif /* CONFIG_SMP */
  49
  50 static int __init profile_setup(char * str)
  51 {
  52         static char __initdata schedstr[] = "schedule";
  53         int par;
  54
  55         if (!strncmp(str, schedstr, strlen(schedstr))) {
  56                 prof_on = SCHED_PROFILING;
  57                 if (str[strlen(schedstr)] == ',')
  58                         str += strlen(schedstr) + 1;
  59                 if (get_option(&str, &par))
  60                         prof_shift = par;
  61                 printk(KERN_INFO
  62                         "kernel schedule profiling enabled (shift: %ld)\n",
  63                         prof_shift);
  64         } else if (get_option(&str, &par)) {
  65                 prof_shift = par;
  66                 prof_on = CPU_PROFILING;
  67                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  68                         prof_shift);
  69         }
  70         return 1;
  71 }
  72 __setup("profile=", profile_setup);
  73
  74
  75 void __init profile_init(void)
  76 {
  77         if (!prof_on)
  78                 return;
  79
  80         /* only text is profiled */
  81         prof_len = (_etext - _stext) >> prof_shift;
  82         prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
  83 }
  84
  85 /* Profile event notifications */
  86
  87 #ifdef CONFIG_PROFILING
  88
  89 static DECLARE_RWSEM(profile_rwsem);
  90 static DEFINE_RWLOCK(handoff_lock);
  91 static struct notifier_block * task_exit_notifier;
  92 static struct notifier_block * task_free_notifier;
  93 static struct notifier_block * munmap_notifier;
  94
  95 void profile_task_exit(struct task_struct * task)
  96 {
  97         down_read(&profile_rwsem);
  98         notifier_call_chain(&task_exit_notifier, 0, task);
  99         up_read(&profile_rwsem);
 100 }
 101
 102 int profile_handoff_task(struct task_struct * task)
 103 {
 104         int ret;
 105         read_lock(&handoff_lock);
 106         ret = notifier_call_chain(&task_free_notifier, 0, task);
 107         read_unlock(&handoff_lock);
 108         return (ret == NOTIFY_OK) ? 1 : 0;
 109 }
 110
 111 void profile_munmap(unsigned long addr)
 112 {
 113         down_read(&profile_rwsem);
 114         notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 115         up_read(&profile_rwsem);
 116 }
 117
 118 int task_handoff_register(struct notifier_block * n)
 119 {
 120         int err = -EINVAL;
 121
 122         write_lock(&handoff_lock);
 123         err = notifier_chain_register(&task_free_notifier, n);
 124         write_unlock(&handoff_lock);
 125         return err;
 126 }
 127
 128 int task_handoff_unregister(struct notifier_block * n)
 129 {
 130         int err = -EINVAL;
 131
 132         write_lock(&handoff_lock);
 133         err = notifier_chain_unregister(&task_free_notifier, n);
 134         write_unlock(&handoff_lock);
 135         return err;
 136 }
 137
 138 int profile_event_register(enum profile_type type, struct notifier_block * n)
 139 {
 140         int err = -EINVAL;
 141
 142         down_write(&profile_rwsem);
 143
 144         switch (type) {
 145                 case PROFILE_TASK_EXIT:
 146                         err = notifier_chain_register(&task_exit_notifier, n);
 147                         break;
 148                 case PROFILE_MUNMAP:
 149                         err = notifier_chain_register(&munmap_notifier, n);
 150                         break;
 151         }
 152
 153         up_write(&profile_rwsem);
 154
 155         return err;
 156 }
 157
 158
 159 int profile_event_unregister(enum profile_type type, struct notifier_block * n)
 160 {
 161         int err = -EINVAL;
 162
 163         down_write(&profile_rwsem);
 164
 165         switch (type) {
 166                 case PROFILE_TASK_EXIT:
 167                         err = notifier_chain_unregister(&task_exit_notifier, n);
 168                         break;
 169                 case PROFILE_MUNMAP:
 170                         err = notifier_chain_unregister(&munmap_notifier, n);
 171                         break;
 172         }
 173
 174         up_write(&profile_rwsem);
 175         return err;
 176 }
 177
 178 int register_timer_hook(int (*hook)(struct pt_regs *))
 179 {
 180         if (timer_hook)
 181                 return -EBUSY;
 182         timer_hook = hook;
 183         return 0;
 184 }
 185
 186 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 187 {
 188         WARN_ON(hook != timer_hook);
 189         timer_hook = NULL;
 190         /* make sure all CPUs see the NULL hook */
 191         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 192 }
 193
 194 EXPORT_SYMBOL_GPL(register_timer_hook);
 195 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 196 EXPORT_SYMBOL_GPL(task_handoff_register);
 197 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 198
 199 #endif /* CONFIG_PROFILING */
 200
 201 EXPORT_SYMBOL_GPL(profile_event_register);
 202 EXPORT_SYMBOL_GPL(profile_event_unregister);
 203
 204 #ifdef CONFIG_SMP
 205 /*
 206  * Each cpu has a pair of open-addressed hashtables for pending
 207  * profile hits. read_profile() IPI's all cpus to request them
 208  * to flip buffers and flushes their contents to prof_buffer itself.
 209  * Flip requests are serialized by the profile_flip_mutex. The sole
 210  * use of having a second hashtable is for avoiding cacheline
 211  * contention that would otherwise happen during flushes of pending
 212  * profile hits required for the accuracy of reported profile hits
 213  * and so resurrect the interrupt livelock issue.
 214  *
 215  * The open-addressed hashtables are indexed by profile buffer slot
 216  * and hold the number of pending hits to that profile buffer slot on
 217  * a cpu in an entry. When the hashtable overflows, all pending hits
 218  * are accounted to their corresponding profile buffer slots with
 219  * atomic_add() and the hashtable emptied. As numerous pending hits
 220  * may be accounted to a profile buffer slot in a hashtable entry,
 221  * this amortizes a number of atomic profile buffer increments likely
 222  * to be far larger than the number of entries in the hashtable,
 223  * particularly given that the number of distinct profile buffer
 224  * positions to which hits are accounted during short intervals (e.g.
 225  * several seconds) is usually very small. Exclusion from buffer
 226  * flipping is provided by interrupt disablement (note that for
 227  * SCHED_PROFILING profile_hit() may be called from process context).
 228  * The hash function is meant to be lightweight as opposed to strong,
 229  * and was vaguely inspired by ppc64 firmware-supported inverted
 230  * pagetable hash functions, but uses a full hashtable full of finite
 231  * collision chains, not just pairs of them.
 232  *
 233  * -- wli
 234  */
 235 static void __profile_flip_buffers(void *unused)
 236 {
 237         int cpu = smp_processor_id();
 238
 239         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 240 }
 241
 242 static void profile_flip_buffers(void)
 243 {
 244         int i, j, cpu;
 245
 246         down(&profile_flip_mutex);
 247         j = per_cpu(cpu_profile_flip, get_cpu());
 248         put_cpu();
 249         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 250         for_each_online_cpu(cpu) {
 251                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 252                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 253                         if (!hits[i].hits) {
 254                                 if (hits[i].pc)
 255                                         hits[i].pc = 0;
 256                                 continue;
 257                         }
 258                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 259                         hits[i].hits = hits[i].pc = 0;
 260                 }
 261         }
 262         up(&profile_flip_mutex);
 263 }
 264
 265 static void profile_discard_flip_buffers(void)
 266 {
 267         int i, cpu;
 268
 269         down(&profile_flip_mutex);
 270         i = per_cpu(cpu_profile_flip, get_cpu());
 271         put_cpu();
 272         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 273         for_each_online_cpu(cpu) {
 274                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 275                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 276         }
 277         up(&profile_flip_mutex);
 278 }
 279
 280 void profile_hit(int type, void *__pc)
 281 {
 282         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 283         int i, j, cpu;
 284         struct profile_hit *hits;
 285
 286         if (prof_on != type || !prof_buffer)
 287                 return;
 288         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 289         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 290         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 291         cpu = get_cpu();
 292         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 293         if (!hits) {
 294                 put_cpu();
 295                 return;
 296         }
 297         local_irq_save(flags);
 298         do {
 299                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 300                         if (hits[i + j].pc == pc) {
 301                                 hits[i + j].hits++;
 302                                 goto out;
 303                         } else if (!hits[i + j].hits) {
 304                                 hits[i + j].pc = pc;
 305                                 hits[i + j].hits = 1;
 306                                 goto out;
 307                         }
 308                 }
 309                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 310         } while (i != primary);
 311         atomic_inc(&prof_buffer[pc]);
 312         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 313                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 314                 hits[i].pc = hits[i].hits = 0;
 315         }
 316 out:
 317         local_irq_restore(flags);
 318         put_cpu();
 319 }
 320
 321 #ifdef CONFIG_HOTPLUG_CPU
 322 static int __devinit profile_cpu_callback(struct notifier_block *info,
 323                                         unsigned long action, void *__cpu)
 324 {
 325         int node, cpu = (unsigned long)__cpu;
 326         struct page *page;
 327
 328         switch (action) {
 329         case CPU_UP_PREPARE:
 330                 node = cpu_to_node(cpu);
 331                 per_cpu(cpu_profile_flip, cpu) = 0;
 332                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 333                         page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 334                         if (!page)
 335                                 return NOTIFY_BAD;
 336                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 337                 }
 338                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 339                         page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 340                         if (!page)
 341                                 goto out_free;
 342                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 343                 }
 344                 break;
 345         out_free:
 346                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 347                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 348                 __free_page(page);
 349                 return NOTIFY_BAD;
 350         case CPU_ONLINE:
 351                 cpu_set(cpu, prof_cpu_mask);
 352                 break;
 353         case CPU_UP_CANCELED:
 354         case CPU_DEAD:
 355                 cpu_clear(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_HOTPLUG_CPU */
 371 #else /* !CONFIG_SMP */
 372 #define profile_flip_buffers()          do { } while (0)
 373 #define profile_discard_flip_buffers()  do { } while (0)
 374
 375 void profile_hit(int type, void *__pc)
 376 {
 377         unsigned long pc;
 378
 379         if (prof_on != type || !prof_buffer)
 380                 return;
 381         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 382         atomic_inc(&prof_buffer[min(pc, prof_len - 1)]);
 383 }
 384 #endif /* !CONFIG_SMP */
 385
 386 void profile_tick(int type, struct pt_regs *regs)
 387 {
 388         if (type == CPU_PROFILING && timer_hook)
 389                 timer_hook(regs);
 390         if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
 391                 profile_hit(type, (void *)profile_pc(regs));
 392 }
 393
 394 #ifdef CONFIG_PROC_FS
 395 #include <linux/proc_fs.h>
 396 #include <asm/uaccess.h>
 397 #include <asm/ptrace.h>
 398
 399 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
 400                         int count, int *eof, void *data)
 401 {
 402         int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
 403         if (count - len < 2)
 404                 return -EINVAL;
 405         len += sprintf(page + len, "\n");
 406         return len;
 407 }
 408
 409 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer,
 410                                         unsigned long count, void *data)
 411 {
 412         cpumask_t *mask = (cpumask_t *)data;
 413         unsigned long full_count = count, err;
 414         cpumask_t new_value;
 415
 416         err = cpumask_parse(buffer, count, new_value);
 417         if (err)
 418                 return err;
 419
 420         *mask = new_value;
 421         return full_count;
 422 }
 423
 424 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 425 {
 426         struct proc_dir_entry *entry;
 427
 428         /* create /proc/irq/prof_cpu_mask */
 429         if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir)))
 430                 return;
 431         entry->nlink = 1;
 432         entry->data = (void *)&prof_cpu_mask;
 433         entry->read_proc = prof_cpu_mask_read_proc;
 434         entry->write_proc = prof_cpu_mask_write_proc;
 435 }
 436
 437 /*
 438  * This function accesses profiling information. The returned data is
 439  * binary: the sampling step and the actual contents of the profile
 440  * buffer. Use of the program readprofile is recommended in order to
 441  * get meaningful info out of these data.
 442  */
 443 static ssize_t
 444 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 445 {
 446         unsigned long p = *ppos;
 447         ssize_t read;
 448         char * pnt;
 449         unsigned int sample_step = 1 << prof_shift;
 450
 451         profile_flip_buffers();
 452         if (p >= (prof_len+1)*sizeof(unsigned int))
 453                 return 0;
 454         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 455                 count = (prof_len+1)*sizeof(unsigned int) - p;
 456         read = 0;
 457
 458         while (p < sizeof(unsigned int) && count > 0) {
 459                 put_user(*((char *)(&sample_step)+p),buf);
 460                 buf++; p++; count--; read++;
 461         }
 462         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 463         if (copy_to_user(buf,(void *)pnt,count))
 464                 return -EFAULT;
 465         read += count;
 466         *ppos += read;
 467         return read;
 468 }
 469
 470 /*
 471  * Writing to /proc/profile resets the counters
 472  *
 473  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 474  * interrupt frequency, on architectures that support this.
 475  */
 476 static ssize_t write_profile(struct file *file, const char __user *buf,
 477                              size_t count, loff_t *ppos)
 478 {
 479 #ifdef CONFIG_SMP
 480         extern int setup_profiling_timer (unsigned int multiplier);
 481
 482         if (count == sizeof(int)) {
 483                 unsigned int multiplier;
 484
 485                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 486                         return -EFAULT;
 487
 488                 if (setup_profiling_timer(multiplier))
 489                         return -EINVAL;
 490         }
 491 #endif
 492         profile_discard_flip_buffers();
 493         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 494         return count;
 495 }
 496
 497 static struct file_operations proc_profile_operations = {
 498         .read           = read_profile,
 499         .write          = write_profile,
 500 };
 501
 502 #ifdef CONFIG_SMP
 503 static void __init profile_nop(void *unused)
 504 {
 505 }
 506
 507 static int __init create_hash_tables(void)
 508 {
 509         int cpu;
 510
 511         for_each_online_cpu(cpu) {
 512                 int node = cpu_to_node(cpu);
 513                 struct page *page;
 514
 515                 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 516                 if (!page)
 517                         goto out_cleanup;
 518                 per_cpu(cpu_profile_hits, cpu)[1]
 519                                 = (struct profile_hit *)page_address(page);
 520                 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 521                 if (!page)
 522                         goto out_cleanup;
 523                 per_cpu(cpu_profile_hits, cpu)[0]
 524                                 = (struct profile_hit *)page_address(page);
 525         }
 526         return 0;
 527 out_cleanup:
 528         prof_on = 0;
 529         smp_mb();
 530         on_each_cpu(profile_nop, NULL, 0, 1);
 531         for_each_online_cpu(cpu) {
 532                 struct page *page;
 533
 534                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 535                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 536                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 537                         __free_page(page);
 538                 }
 539                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 540                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 541                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 542                         __free_page(page);
 543                 }
 544         }
 545         return -1;
 546 }
 547 #else
 548 #define create_hash_tables()                    ({ 0; })
 549 #endif
 550
 551 static int __init create_proc_profile(void)
 552 {
 553         struct proc_dir_entry *entry;
 554
 555         if (!prof_on)
 556                 return 0;
 557         if (create_hash_tables())
 558                 return -1;
 559         if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL)))
 560                 return 0;
 561         entry->proc_fops = &proc_profile_operations;
 562         entry->size = (1+prof_len) * sizeof(atomic_t);
 563         hotcpu_notifier(profile_cpu_callback, 0);
 564         return 0;
 565 }
 566 module_init(create_proc_profile);
 567 #endif /* CONFIG_PROC_FS */