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