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