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         int par;
  53
  54         if (!strncmp(str, "schedule", 8)) {
  55                 prof_on = SCHED_PROFILING;
  56                 printk(KERN_INFO "kernel schedule profiling enabled\n");
  57                 if (str[7] == ',')
  58                         str += 8;
  59         }
  60         if (get_option(&str,&par)) {
  61                 prof_shift = par;
  62                 prof_on = CPU_PROFILING;
  63                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  64                         prof_shift);
  65         }
  66         return 1;
  67 }
  68 __setup("profile=", profile_setup);
  69
  70
  71 void __init profile_init(void)
  72 {
  73         if (!prof_on)
  74                 return;
  75
  76         /* only text is profiled */
  77         prof_len = (_etext - _stext) >> prof_shift;
  78         prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
  79 }
  80
  81 /* Profile event notifications */
  82
  83 #ifdef CONFIG_PROFILING
  84
  85 static DECLARE_RWSEM(profile_rwsem);
  86 static DEFINE_RWLOCK(handoff_lock);
  87 static struct notifier_block * task_exit_notifier;
  88 static struct notifier_block * task_free_notifier;
  89 static struct notifier_block * munmap_notifier;
  90
  91 void profile_task_exit(struct task_struct * task)
  92 {
  93         down_read(&profile_rwsem);
  94         notifier_call_chain(&task_exit_notifier, 0, task);
  95         up_read(&profile_rwsem);
  96 }
  97
  98 int profile_handoff_task(struct task_struct * task)
  99 {
 100         int ret;
 101         read_lock(&handoff_lock);
 102         ret = notifier_call_chain(&task_free_notifier, 0, task);
 103         read_unlock(&handoff_lock);
 104         return (ret == NOTIFY_OK) ? 1 : 0;
 105 }
 106
 107 void profile_munmap(unsigned long addr)
 108 {
 109         down_read(&profile_rwsem);
 110         notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 111         up_read(&profile_rwsem);
 112 }
 113
 114 int task_handoff_register(struct notifier_block * n)
 115 {
 116         int err = -EINVAL;
 117
 118         write_lock(&handoff_lock);
 119         err = notifier_chain_register(&task_free_notifier, n);
 120         write_unlock(&handoff_lock);
 121         return err;
 122 }
 123
 124 int task_handoff_unregister(struct notifier_block * n)
 125 {
 126         int err = -EINVAL;
 127
 128         write_lock(&handoff_lock);
 129         err = notifier_chain_unregister(&task_free_notifier, n);
 130         write_unlock(&handoff_lock);
 131         return err;
 132 }
 133
 134 int profile_event_register(enum profile_type type, struct notifier_block * n)
 135 {
 136         int err = -EINVAL;
 137
 138         down_write(&profile_rwsem);
 139
 140         switch (type) {
 141                 case PROFILE_TASK_EXIT:
 142                         err = notifier_chain_register(&task_exit_notifier, n);
 143                         break;
 144                 case PROFILE_MUNMAP:
 145                         err = notifier_chain_register(&munmap_notifier, n);
 146                         break;
 147         }
 148
 149         up_write(&profile_rwsem);
 150
 151         return err;
 152 }
 153
 154
 155 int profile_event_unregister(enum profile_type type, struct notifier_block * n)
 156 {
 157         int err = -EINVAL;
 158
 159         down_write(&profile_rwsem);
 160
 161         switch (type) {
 162                 case PROFILE_TASK_EXIT:
 163                         err = notifier_chain_unregister(&task_exit_notifier, n);
 164                         break;
 165                 case PROFILE_MUNMAP:
 166                         err = notifier_chain_unregister(&munmap_notifier, n);
 167                         break;
 168         }
 169
 170         up_write(&profile_rwsem);
 171         return err;
 172 }
 173
 174 int register_timer_hook(int (*hook)(struct pt_regs *))
 175 {
 176         if (timer_hook)
 177                 return -EBUSY;
 178         timer_hook = hook;
 179         return 0;
 180 }
 181
 182 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 183 {
 184         WARN_ON(hook != timer_hook);
 185         timer_hook = NULL;
 186         /* make sure all CPUs see the NULL hook */
 187         synchronize_kernel();
 188 }
 189
 190 EXPORT_SYMBOL_GPL(register_timer_hook);
 191 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 192 EXPORT_SYMBOL_GPL(task_handoff_register);
 193 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 194
 195 #endif /* CONFIG_PROFILING */
 196
 197 EXPORT_SYMBOL_GPL(profile_event_register);
 198 EXPORT_SYMBOL_GPL(profile_event_unregister);
 199
 200 #ifdef CONFIG_SMP
 201 /*
 202  * Each cpu has a pair of open-addressed hashtables for pending
 203  * profile hits. read_profile() IPI's all cpus to request them
 204  * to flip buffers and flushes their contents to prof_buffer itself.
 205  * Flip requests are serialized by the profile_flip_mutex. The sole
 206  * use of having a second hashtable is for avoiding cacheline
 207  * contention that would otherwise happen during flushes of pending
 208  * profile hits required for the accuracy of reported profile hits
 209  * and so resurrect the interrupt livelock issue.
 210  *
 211  * The open-addressed hashtables are indexed by profile buffer slot
 212  * and hold the number of pending hits to that profile buffer slot on
 213  * a cpu in an entry. When the hashtable overflows, all pending hits
 214  * are accounted to their corresponding profile buffer slots with
 215  * atomic_add() and the hashtable emptied. As numerous pending hits
 216  * may be accounted to a profile buffer slot in a hashtable entry,
 217  * this amortizes a number of atomic profile buffer increments likely
 218  * to be far larger than the number of entries in the hashtable,
 219  * particularly given that the number of distinct profile buffer
 220  * positions to which hits are accounted during short intervals (e.g.
 221  * several seconds) is usually very small. Exclusion from buffer
 222  * flipping is provided by interrupt disablement (note that for
 223  * SCHED_PROFILING profile_hit() may be called from process context).
 224  * The hash function is meant to be lightweight as opposed to strong,
 225  * and was vaguely inspired by ppc64 firmware-supported inverted
 226  * pagetable hash functions, but uses a full hashtable full of finite
 227  * collision chains, not just pairs of them.
 228  *
 229  * -- wli
 230  */
 231 static void __profile_flip_buffers(void *unused)
 232 {
 233         int cpu = smp_processor_id();
 234
 235         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 236 }
 237
 238 static void profile_flip_buffers(void)
 239 {
 240         int i, j, cpu;
 241
 242         down(&profile_flip_mutex);
 243         j = per_cpu(cpu_profile_flip, get_cpu());
 244         put_cpu();
 245         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 246         for_each_online_cpu(cpu) {
 247                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 248                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 249                         if (!hits[i].hits) {
 250                                 if (hits[i].pc)
 251                                         hits[i].pc = 0;
 252                                 continue;
 253                         }
 254                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 255                         hits[i].hits = hits[i].pc = 0;
 256                 }
 257         }
 258         up(&profile_flip_mutex);
 259 }
 260
 261 static void profile_discard_flip_buffers(void)
 262 {
 263         int i, cpu;
 264
 265         down(&profile_flip_mutex);
 266         i = per_cpu(cpu_profile_flip, get_cpu());
 267         put_cpu();
 268         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 269         for_each_online_cpu(cpu) {
 270                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 271                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 272         }
 273         up(&profile_flip_mutex);
 274 }
 275
 276 void profile_hit(int type, void *__pc)
 277 {
 278         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 279         int i, j, cpu;
 280         struct profile_hit *hits;
 281
 282         if (prof_on != type || !prof_buffer)
 283                 return;
 284         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 285         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 286         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 287         cpu = get_cpu();
 288         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 289         if (!hits) {
 290                 put_cpu();
 291                 return;
 292         }
 293         local_irq_save(flags);
 294         do {
 295                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 296                         if (hits[i + j].pc == pc) {
 297                                 hits[i + j].hits++;
 298                                 goto out;
 299                         } else if (!hits[i + j].hits) {
 300                                 hits[i + j].pc = pc;
 301                                 hits[i + j].hits = 1;
 302                                 goto out;
 303                         }
 304                 }
 305                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 306         } while (i != primary);
 307         atomic_inc(&prof_buffer[pc]);
 308         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 309                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 310                 hits[i].pc = hits[i].hits = 0;
 311         }
 312 out:
 313         local_irq_restore(flags);
 314         put_cpu();
 315 }
 316
 317 #ifdef CONFIG_HOTPLUG_CPU
 318 static int __devinit profile_cpu_callback(struct notifier_block *info,
 319                                         unsigned long action, void *__cpu)
 320 {
 321         int node, cpu = (unsigned long)__cpu;
 322         struct page *page;
 323
 324         switch (action) {
 325         case CPU_UP_PREPARE:
 326                 node = cpu_to_node(cpu);
 327                 per_cpu(cpu_profile_flip, cpu) = 0;
 328                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 329                         page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 330                         if (!page)
 331                                 return NOTIFY_BAD;
 332                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 333                 }
 334                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 335                         page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 336                         if (!page)
 337                                 goto out_free;
 338                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 339                 }
 340                 break;
 341         out_free:
 342                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 343                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 344                 __free_page(page);
 345                 return NOTIFY_BAD;
 346         case CPU_ONLINE:
 347                 cpu_set(cpu, prof_cpu_mask);
 348                 break;
 349         case CPU_UP_CANCELED:
 350         case CPU_DEAD:
 351                 cpu_clear(cpu, prof_cpu_mask);
 352                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 353                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 354                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 355                         __free_page(page);
 356                 }
 357                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 358                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 359                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 360                         __free_page(page);
 361                 }
 362                 break;
 363         }
 364         return NOTIFY_OK;
 365 }
 366 #endif /* CONFIG_HOTPLUG_CPU */
 367 #else /* !CONFIG_SMP */
 368 #define profile_flip_buffers()          do { } while (0)
 369 #define profile_discard_flip_buffers()  do { } while (0)
 370
 371 void profile_hit(int type, void *__pc)
 372 {
 373         unsigned long pc;
 374
 375         if (prof_on != type || !prof_buffer)
 376                 return;
 377         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 378         atomic_inc(&prof_buffer[min(pc, prof_len - 1)]);
 379 }
 380 #endif /* !CONFIG_SMP */
 381
 382 void profile_tick(int type, struct pt_regs *regs)
 383 {
 384         if (type == CPU_PROFILING && timer_hook)
 385                 timer_hook(regs);
 386         if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
 387                 profile_hit(type, (void *)profile_pc(regs));
 388 }
 389
 390 #ifdef CONFIG_PROC_FS
 391 #include <linux/proc_fs.h>
 392 #include <asm/uaccess.h>
 393 #include <asm/ptrace.h>
 394
 395 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
 396                         int count, int *eof, void *data)
 397 {
 398         int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
 399         if (count - len < 2)
 400                 return -EINVAL;
 401         len += sprintf(page + len, "\n");
 402         return len;
 403 }
 404
 405 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer,
 406                                         unsigned long count, void *data)
 407 {
 408         cpumask_t *mask = (cpumask_t *)data;
 409         unsigned long full_count = count, err;
 410         cpumask_t new_value;
 411
 412         err = cpumask_parse(buffer, count, new_value);
 413         if (err)
 414                 return err;
 415
 416         *mask = new_value;
 417         return full_count;
 418 }
 419
 420 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 421 {
 422         struct proc_dir_entry *entry;
 423
 424         /* create /proc/irq/prof_cpu_mask */
 425         if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir)))
 426                 return;
 427         entry->nlink = 1;
 428         entry->data = (void *)&prof_cpu_mask;
 429         entry->read_proc = prof_cpu_mask_read_proc;
 430         entry->write_proc = prof_cpu_mask_write_proc;
 431 }
 432
 433 /*
 434  * This function accesses profiling information. The returned data is
 435  * binary: the sampling step and the actual contents of the profile
 436  * buffer. Use of the program readprofile is recommended in order to
 437  * get meaningful info out of these data.
 438  */
 439 static ssize_t
 440 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 441 {
 442         unsigned long p = *ppos;
 443         ssize_t read;
 444         char * pnt;
 445         unsigned int sample_step = 1 << prof_shift;
 446
 447         profile_flip_buffers();
 448         if (p >= (prof_len+1)*sizeof(unsigned int))
 449                 return 0;
 450         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 451                 count = (prof_len+1)*sizeof(unsigned int) - p;
 452         read = 0;
 453
 454         while (p < sizeof(unsigned int) && count > 0) {
 455                 put_user(*((char *)(&sample_step)+p),buf);
 456                 buf++; p++; count--; read++;
 457         }
 458         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 459         if (copy_to_user(buf,(void *)pnt,count))
 460                 return -EFAULT;
 461         read += count;
 462         *ppos += read;
 463         return read;
 464 }
 465
 466 /*
 467  * Writing to /proc/profile resets the counters
 468  *
 469  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 470  * interrupt frequency, on architectures that support this.
 471  */
 472 static ssize_t write_profile(struct file *file, const char __user *buf,
 473                              size_t count, loff_t *ppos)
 474 {
 475 #ifdef CONFIG_SMP
 476         extern int setup_profiling_timer (unsigned int multiplier);
 477
 478         if (count == sizeof(int)) {
 479                 unsigned int multiplier;
 480
 481                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 482                         return -EFAULT;
 483
 484                 if (setup_profiling_timer(multiplier))
 485                         return -EINVAL;
 486         }
 487 #endif
 488         profile_discard_flip_buffers();
 489         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 490         return count;
 491 }
 492
 493 static struct file_operations proc_profile_operations = {
 494         .read           = read_profile,
 495         .write          = write_profile,
 496 };
 497
 498 #ifdef CONFIG_SMP
 499 static void __init profile_nop(void *unused)
 500 {
 501 }
 502
 503 static int __init create_hash_tables(void)
 504 {
 505         int cpu;
 506
 507         for_each_online_cpu(cpu) {
 508                 int node = cpu_to_node(cpu);
 509                 struct page *page;
 510
 511                 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 512                 if (!page)
 513                         goto out_cleanup;
 514                 per_cpu(cpu_profile_hits, cpu)[1]
 515                                 = (struct profile_hit *)page_address(page);
 516                 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 517                 if (!page)
 518                         goto out_cleanup;
 519                 per_cpu(cpu_profile_hits, cpu)[0]
 520                                 = (struct profile_hit *)page_address(page);
 521         }
 522         return 0;
 523 out_cleanup:
 524         prof_on = 0;
 525         mb();
 526         on_each_cpu(profile_nop, NULL, 0, 1);
 527         for_each_online_cpu(cpu) {
 528                 struct page *page;
 529
 530                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 531                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 532                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 533                         __free_page(page);
 534                 }
 535                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 536                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 537                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 538                         __free_page(page);
 539                 }
 540         }
 541         return -1;
 542 }
 543 #else
 544 #define create_hash_tables()                    ({ 0; })
 545 #endif
 546
 547 static int __init create_proc_profile(void)
 548 {
 549         struct proc_dir_entry *entry;
 550
 551         if (!prof_on)
 552                 return 0;
 553         if (create_hash_tables())
 554                 return -1;
 555         if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL)))
 556                 return 0;
 557         entry->proc_fops = &proc_profile_operations;
 558         entry->size = (1+prof_len) * sizeof(atomic_t);
 559         hotcpu_notifier(profile_cpu_callback, 0);
 560         return 0;
 561 }
 562 module_init(create_proc_profile);
 563 #endif /* CONFIG_PROC_FS */