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_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 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                 return 0;
 117         }
 118
 119         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
 120         if (prof_buffer)
 121                 return 0;
 122
 123         prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO);
 124         if (prof_buffer)
 125                 return 0;
 126
 127         prof_buffer = vmalloc(buffer_bytes);
 128         if (prof_buffer)
 129                 return 0;
 130
 131         return -ENOMEM;
 132 }
 133
 134 /* Profile event notifications */
 135
 136 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 137 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 138 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 139
 140 void profile_task_exit(struct task_struct *task)
 141 {
 142         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 143 }
 144
 145 int profile_handoff_task(struct task_struct *task)
 146 {
 147         int ret;
 148         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 149         return (ret == NOTIFY_OK) ? 1 : 0;
 150 }
 151
 152 void profile_munmap(unsigned long addr)
 153 {
 154         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 155 }
 156
 157 int task_handoff_register(struct notifier_block *n)
 158 {
 159         return atomic_notifier_chain_register(&task_free_notifier, n);
 160 }
 161 EXPORT_SYMBOL_GPL(task_handoff_register);
 162
 163 int task_handoff_unregister(struct notifier_block *n)
 164 {
 165         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 166 }
 167 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 168
 169 int profile_event_register(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_register(
 176                                 &task_exit_notifier, n);
 177                 break;
 178         case PROFILE_MUNMAP:
 179                 err = blocking_notifier_chain_register(
 180                                 &munmap_notifier, n);
 181                 break;
 182         }
 183
 184         return err;
 185 }
 186 EXPORT_SYMBOL_GPL(profile_event_register);
 187
 188 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 189 {
 190         int err = -EINVAL;
 191
 192         switch (type) {
 193         case PROFILE_TASK_EXIT:
 194                 err = blocking_notifier_chain_unregister(
 195                                 &task_exit_notifier, n);
 196                 break;
 197         case PROFILE_MUNMAP:
 198                 err = blocking_notifier_chain_unregister(
 199                                 &munmap_notifier, n);
 200                 break;
 201         }
 202
 203         return err;
 204 }
 205 EXPORT_SYMBOL_GPL(profile_event_unregister);
 206
 207 int register_timer_hook(int (*hook)(struct pt_regs *))
 208 {
 209         if (timer_hook)
 210                 return -EBUSY;
 211         timer_hook = hook;
 212         return 0;
 213 }
 214 EXPORT_SYMBOL_GPL(register_timer_hook);
 215
 216 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 217 {
 218         WARN_ON(hook != timer_hook);
 219         timer_hook = NULL;
 220         /* make sure all CPUs see the NULL hook */
 221         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 222 }
 223 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 224
 225
 226 #ifdef CONFIG_SMP
 227 /*
 228  * Each cpu has a pair of open-addressed hashtables for pending
 229  * profile hits. read_profile() IPI's all cpus to request them
 230  * to flip buffers and flushes their contents to prof_buffer itself.
 231  * Flip requests are serialized by the profile_flip_mutex. The sole
 232  * use of having a second hashtable is for avoiding cacheline
 233  * contention that would otherwise happen during flushes of pending
 234  * profile hits required for the accuracy of reported profile hits
 235  * and so resurrect the interrupt livelock issue.
 236  *
 237  * The open-addressed hashtables are indexed by profile buffer slot
 238  * and hold the number of pending hits to that profile buffer slot on
 239  * a cpu in an entry. When the hashtable overflows, all pending hits
 240  * are accounted to their corresponding profile buffer slots with
 241  * atomic_add() and the hashtable emptied. As numerous pending hits
 242  * may be accounted to a profile buffer slot in a hashtable entry,
 243  * this amortizes a number of atomic profile buffer increments likely
 244  * to be far larger than the number of entries in the hashtable,
 245  * particularly given that the number of distinct profile buffer
 246  * positions to which hits are accounted during short intervals (e.g.
 247  * several seconds) is usually very small. Exclusion from buffer
 248  * flipping is provided by interrupt disablement (note that for
 249  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 250  * process context).
 251  * The hash function is meant to be lightweight as opposed to strong,
 252  * and was vaguely inspired by ppc64 firmware-supported inverted
 253  * pagetable hash functions, but uses a full hashtable full of finite
 254  * collision chains, not just pairs of them.
 255  *
 256  * -- wli
 257  */
 258 static void __profile_flip_buffers(void *unused)
 259 {
 260         int cpu = smp_processor_id();
 261
 262         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 263 }
 264
 265 static void profile_flip_buffers(void)
 266 {
 267         int i, j, cpu;
 268
 269         mutex_lock(&profile_flip_mutex);
 270         j = per_cpu(cpu_profile_flip, get_cpu());
 271         put_cpu();
 272         on_each_cpu(__profile_flip_buffers, NULL, 1);
 273         for_each_online_cpu(cpu) {
 274                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 275                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 276                         if (!hits[i].hits) {
 277                                 if (hits[i].pc)
 278                                         hits[i].pc = 0;
 279                                 continue;
 280                         }
 281                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 282                         hits[i].hits = hits[i].pc = 0;
 283                 }
 284         }
 285         mutex_unlock(&profile_flip_mutex);
 286 }
 287
 288 static void profile_discard_flip_buffers(void)
 289 {
 290         int i, cpu;
 291
 292         mutex_lock(&profile_flip_mutex);
 293         i = per_cpu(cpu_profile_flip, get_cpu());
 294         put_cpu();
 295         on_each_cpu(__profile_flip_buffers, NULL, 1);
 296         for_each_online_cpu(cpu) {
 297                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 298                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 299         }
 300         mutex_unlock(&profile_flip_mutex);
 301 }
 302
 303 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 304 {
 305         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 306         int i, j, cpu;
 307         struct profile_hit *hits;
 308
 309         if (prof_on != type || !prof_buffer)
 310                 return;
 311         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 312         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 313         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 314         cpu = get_cpu();
 315         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 316         if (!hits) {
 317                 put_cpu();
 318                 return;
 319         }
 320         /*
 321          * We buffer the global profiler buffer into a per-CPU
 322          * queue and thus reduce the number of global (and possibly
 323          * NUMA-alien) accesses. The write-queue is self-coalescing:
 324          */
 325         local_irq_save(flags);
 326         do {
 327                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 328                         if (hits[i + j].pc == pc) {
 329                                 hits[i + j].hits += nr_hits;
 330                                 goto out;
 331                         } else if (!hits[i + j].hits) {
 332                                 hits[i + j].pc = pc;
 333                                 hits[i + j].hits = nr_hits;
 334                                 goto out;
 335                         }
 336                 }
 337                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 338         } while (i != primary);
 339
 340         /*
 341          * Add the current hit(s) and flush the write-queue out
 342          * to the global buffer:
 343          */
 344         atomic_add(nr_hits, &prof_buffer[pc]);
 345         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 346                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 347                 hits[i].pc = hits[i].hits = 0;
 348         }
 349 out:
 350         local_irq_restore(flags);
 351         put_cpu();
 352 }
 353
 354 static int __cpuinit profile_cpu_callback(struct notifier_block *info,
 355                                         unsigned long action, void *__cpu)
 356 {
 357         int node, cpu = (unsigned long)__cpu;
 358         struct page *page;
 359
 360         switch (action) {
 361         case CPU_UP_PREPARE:
 362         case CPU_UP_PREPARE_FROZEN:
 363                 node = cpu_to_node(cpu);
 364                 per_cpu(cpu_profile_flip, cpu) = 0;
 365                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 366                         page = alloc_pages_node(node,
 367                                         GFP_KERNEL | __GFP_ZERO,
 368                                         0);
 369                         if (!page)
 370                                 return NOTIFY_BAD;
 371                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 372                 }
 373                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 374                         page = alloc_pages_node(node,
 375                                         GFP_KERNEL | __GFP_ZERO,
 376                                         0);
 377                         if (!page)
 378                                 goto out_free;
 379                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 380                 }
 381                 break;
 382 out_free:
 383                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 384                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 385                 __free_page(page);
 386                 return NOTIFY_BAD;
 387         case CPU_ONLINE:
 388         case CPU_ONLINE_FROZEN:
 389                 cpu_set(cpu, prof_cpu_mask);
 390                 break;
 391         case CPU_UP_CANCELED:
 392         case CPU_UP_CANCELED_FROZEN:
 393         case CPU_DEAD:
 394         case CPU_DEAD_FROZEN:
 395                 cpu_clear(cpu, prof_cpu_mask);
 396                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 397                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 398                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 399                         __free_page(page);
 400                 }
 401                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 402                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 403                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 404                         __free_page(page);
 405                 }
 406                 break;
 407         }
 408         return NOTIFY_OK;
 409 }
 410 #else /* !CONFIG_SMP */
 411 #define profile_flip_buffers()          do { } while (0)
 412 #define profile_discard_flip_buffers()  do { } while (0)
 413 #define profile_cpu_callback            NULL
 414
 415 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 416 {
 417         unsigned long pc;
 418
 419         if (prof_on != type || !prof_buffer)
 420                 return;
 421         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 422         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 423 }
 424 #endif /* !CONFIG_SMP */
 425 EXPORT_SYMBOL_GPL(profile_hits);
 426
 427 void profile_tick(int type)
 428 {
 429         struct pt_regs *regs = get_irq_regs();
 430
 431         if (type == CPU_PROFILING && timer_hook)
 432                 timer_hook(regs);
 433         if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
 434                 profile_hit(type, (void *)profile_pc(regs));
 435 }
 436
 437 #ifdef CONFIG_PROC_FS
 438 #include <linux/proc_fs.h>
 439 #include <asm/uaccess.h>
 440 #include <asm/ptrace.h>
 441
 442 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
 443                         int count, int *eof, void *data)
 444 {
 445         int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
 446         if (count - len < 2)
 447                 return -EINVAL;
 448         len += sprintf(page + len, "\n");
 449         return len;
 450 }
 451
 452 static int prof_cpu_mask_write_proc(struct file *file,
 453         const char __user *buffer,  unsigned long count, void *data)
 454 {
 455         cpumask_t *mask = (cpumask_t *)data;
 456         unsigned long full_count = count, err;
 457         cpumask_t new_value;
 458
 459         err = cpumask_parse_user(buffer, count, new_value);
 460         if (err)
 461                 return err;
 462
 463         *mask = new_value;
 464         return full_count;
 465 }
 466
 467 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 468 {
 469         struct proc_dir_entry *entry;
 470
 471         /* create /proc/irq/prof_cpu_mask */
 472         entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
 473         if (!entry)
 474                 return;
 475         entry->data = (void *)&prof_cpu_mask;
 476         entry->read_proc = prof_cpu_mask_read_proc;
 477         entry->write_proc = prof_cpu_mask_write_proc;
 478 }
 479
 480 /*
 481  * This function accesses profiling information. The returned data is
 482  * binary: the sampling step and the actual contents of the profile
 483  * buffer. Use of the program readprofile is recommended in order to
 484  * get meaningful info out of these data.
 485  */
 486 static ssize_t
 487 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 488 {
 489         unsigned long p = *ppos;
 490         ssize_t read;
 491         char *pnt;
 492         unsigned int sample_step = 1 << prof_shift;
 493
 494         profile_flip_buffers();
 495         if (p >= (prof_len+1)*sizeof(unsigned int))
 496                 return 0;
 497         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 498                 count = (prof_len+1)*sizeof(unsigned int) - p;
 499         read = 0;
 500
 501         while (p < sizeof(unsigned int) && count > 0) {
 502                 if (put_user(*((char *)(&sample_step)+p), buf))
 503                         return -EFAULT;
 504                 buf++; p++; count--; read++;
 505         }
 506         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 507         if (copy_to_user(buf, (void *)pnt, count))
 508                 return -EFAULT;
 509         read += count;
 510         *ppos += read;
 511         return read;
 512 }
 513
 514 /*
 515  * Writing to /proc/profile resets the counters
 516  *
 517  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 518  * interrupt frequency, on architectures that support this.
 519  */
 520 static ssize_t write_profile(struct file *file, const char __user *buf,
 521                              size_t count, loff_t *ppos)
 522 {
 523 #ifdef CONFIG_SMP
 524         extern int setup_profiling_timer(unsigned int multiplier);
 525
 526         if (count == sizeof(int)) {
 527                 unsigned int multiplier;
 528
 529                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 530                         return -EFAULT;
 531
 532                 if (setup_profiling_timer(multiplier))
 533                         return -EINVAL;
 534         }
 535 #endif
 536         profile_discard_flip_buffers();
 537         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 538         return count;
 539 }
 540
 541 static const struct file_operations proc_profile_operations = {
 542         .read           = read_profile,
 543         .write          = write_profile,
 544 };
 545
 546 #ifdef CONFIG_SMP
 547 static void profile_nop(void *unused)
 548 {
 549 }
 550
 551 static int create_hash_tables(void)
 552 {
 553         int cpu;
 554
 555         for_each_online_cpu(cpu) {
 556                 int node = cpu_to_node(cpu);
 557                 struct page *page;
 558
 559                 page = alloc_pages_node(node,
 560                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 561                                 0);
 562                 if (!page)
 563                         goto out_cleanup;
 564                 per_cpu(cpu_profile_hits, cpu)[1]
 565                                 = (struct profile_hit *)page_address(page);
 566                 page = alloc_pages_node(node,
 567                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 568                                 0);
 569                 if (!page)
 570                         goto out_cleanup;
 571                 per_cpu(cpu_profile_hits, cpu)[0]
 572                                 = (struct profile_hit *)page_address(page);
 573         }
 574         return 0;
 575 out_cleanup:
 576         prof_on = 0;
 577         smp_mb();
 578         on_each_cpu(profile_nop, NULL, 1);
 579         for_each_online_cpu(cpu) {
 580                 struct page *page;
 581
 582                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 583                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 584                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 585                         __free_page(page);
 586                 }
 587                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 588                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 589                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 590                         __free_page(page);
 591                 }
 592         }
 593         return -1;
 594 }
 595 #else
 596 #define create_hash_tables()                    ({ 0; })
 597 #endif
 598
 599 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 600 {
 601         struct proc_dir_entry *entry;
 602
 603         if (!prof_on)
 604                 return 0;
 605         if (create_hash_tables())
 606                 return -ENOMEM;
 607         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 608                             NULL, &proc_profile_operations);
 609         if (!entry)
 610                 return 0;
 611         entry->size = (1+prof_len) * sizeof(atomic_t);
 612         hotcpu_notifier(profile_cpu_callback, 0);
 613         return 0;
 614 }
 615 module_init(create_proc_profile);
 616 #endif /* CONFIG_PROC_FS */