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 <asm/sections.h>
  26 #include <asm/semaphore.h>
  27 #include <asm/irq_regs.h>
  28 #include <asm/ptrace.h>
  29
  30 struct profile_hit {
  31         u32 pc, hits;
  32 };
  33 #define PROFILE_GRPSHIFT        3
  34 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  35 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  36 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  37
  38 /* Oprofile timer tick hook */
  39 static int (*timer_hook)(struct pt_regs *) __read_mostly;
  40
  41 static atomic_t *prof_buffer;
  42 static unsigned long prof_len, prof_shift;
  43
  44 int prof_on __read_mostly;
  45 EXPORT_SYMBOL_GPL(prof_on);
  46
  47 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
  48 #ifdef CONFIG_SMP
  49 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  50 static DEFINE_PER_CPU(int, cpu_profile_flip);
  51 static DEFINE_MUTEX(profile_flip_mutex);
  52 #endif /* CONFIG_SMP */
  53
  54 static int __init profile_setup(char *str)
  55 {
  56         static char __initdata schedstr[] = "schedule";
  57         static char __initdata sleepstr[] = "sleep";
  58         static char __initdata kvmstr[] = "kvm";
  59         int par;
  60
  61         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  62 #ifdef CONFIG_SCHEDSTATS
  63                 prof_on = SLEEP_PROFILING;
  64                 if (str[strlen(sleepstr)] == ',')
  65                         str += strlen(sleepstr) + 1;
  66                 if (get_option(&str, &par))
  67                         prof_shift = par;
  68                 printk(KERN_INFO
  69                         "kernel sleep profiling enabled (shift: %ld)\n",
  70                         prof_shift);
  71 #else
  72                 printk(KERN_WARNING
  73                         "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  74 #endif /* CONFIG_SCHEDSTATS */
  75         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  76                 prof_on = SCHED_PROFILING;
  77                 if (str[strlen(schedstr)] == ',')
  78                         str += strlen(schedstr) + 1;
  79                 if (get_option(&str, &par))
  80                         prof_shift = par;
  81                 printk(KERN_INFO
  82                         "kernel schedule profiling enabled (shift: %ld)\n",
  83                         prof_shift);
  84         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  85                 prof_on = KVM_PROFILING;
  86                 if (str[strlen(kvmstr)] == ',')
  87                         str += strlen(kvmstr) + 1;
  88                 if (get_option(&str, &par))
  89                         prof_shift = par;
  90                 printk(KERN_INFO
  91                         "kernel KVM profiling enabled (shift: %ld)\n",
  92                         prof_shift);
  93         } else if (get_option(&str, &par)) {
  94                 prof_shift = par;
  95                 prof_on = CPU_PROFILING;
  96                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  97                         prof_shift);
  98         }
  99         return 1;
 100 }
 101 __setup("profile=", profile_setup);
 102
 103
 104 void __init profile_init(void)
 105 {
 106         if (!prof_on)
 107                 return;
 108
 109         /* only text is profiled */
 110         prof_len = (_etext - _stext) >> prof_shift;
 111         prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
 112 }
 113
 114 /* Profile event notifications */
 115
 116 #ifdef CONFIG_PROFILING
 117
 118 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 119 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 120 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 121
 122 void profile_task_exit(struct task_struct *task)
 123 {
 124         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 125 }
 126
 127 int profile_handoff_task(struct task_struct *task)
 128 {
 129         int ret;
 130         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 131         return (ret == NOTIFY_OK) ? 1 : 0;
 132 }
 133
 134 void profile_munmap(unsigned long addr)
 135 {
 136         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 137 }
 138
 139 int task_handoff_register(struct notifier_block *n)
 140 {
 141         return atomic_notifier_chain_register(&task_free_notifier, n);
 142 }
 143 EXPORT_SYMBOL_GPL(task_handoff_register);
 144
 145 int task_handoff_unregister(struct notifier_block *n)
 146 {
 147         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 148 }
 149 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 150
 151 int profile_event_register(enum profile_type type, struct notifier_block *n)
 152 {
 153         int err = -EINVAL;
 154
 155         switch (type) {
 156         case PROFILE_TASK_EXIT:
 157                 err = blocking_notifier_chain_register(
 158                                 &task_exit_notifier, n);
 159                 break;
 160         case PROFILE_MUNMAP:
 161                 err = blocking_notifier_chain_register(
 162                                 &munmap_notifier, n);
 163                 break;
 164         }
 165
 166         return err;
 167 }
 168 EXPORT_SYMBOL_GPL(profile_event_register);
 169
 170 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 171 {
 172         int err = -EINVAL;
 173
 174         switch (type) {
 175         case PROFILE_TASK_EXIT:
 176                 err = blocking_notifier_chain_unregister(
 177                                 &task_exit_notifier, n);
 178                 break;
 179         case PROFILE_MUNMAP:
 180                 err = blocking_notifier_chain_unregister(
 181                                 &munmap_notifier, n);
 182                 break;
 183         }
 184
 185         return err;
 186 }
 187 EXPORT_SYMBOL_GPL(profile_event_unregister);
 188
 189 int register_timer_hook(int (*hook)(struct pt_regs *))
 190 {
 191         if (timer_hook)
 192                 return -EBUSY;
 193         timer_hook = hook;
 194         return 0;
 195 }
 196 EXPORT_SYMBOL_GPL(register_timer_hook);
 197
 198 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 199 {
 200         WARN_ON(hook != timer_hook);
 201         timer_hook = NULL;
 202         /* make sure all CPUs see the NULL hook */
 203         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 204 }
 205 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 206
 207 #endif /* CONFIG_PROFILING */
 208
 209
 210 #ifdef CONFIG_SMP
 211 /*
 212  * Each cpu has a pair of open-addressed hashtables for pending
 213  * profile hits. read_profile() IPI's all cpus to request them
 214  * to flip buffers and flushes their contents to prof_buffer itself.
 215  * Flip requests are serialized by the profile_flip_mutex. The sole
 216  * use of having a second hashtable is for avoiding cacheline
 217  * contention that would otherwise happen during flushes of pending
 218  * profile hits required for the accuracy of reported profile hits
 219  * and so resurrect the interrupt livelock issue.
 220  *
 221  * The open-addressed hashtables are indexed by profile buffer slot
 222  * and hold the number of pending hits to that profile buffer slot on
 223  * a cpu in an entry. When the hashtable overflows, all pending hits
 224  * are accounted to their corresponding profile buffer slots with
 225  * atomic_add() and the hashtable emptied. As numerous pending hits
 226  * may be accounted to a profile buffer slot in a hashtable entry,
 227  * this amortizes a number of atomic profile buffer increments likely
 228  * to be far larger than the number of entries in the hashtable,
 229  * particularly given that the number of distinct profile buffer
 230  * positions to which hits are accounted during short intervals (e.g.
 231  * several seconds) is usually very small. Exclusion from buffer
 232  * flipping is provided by interrupt disablement (note that for
 233  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 234  * process context).
 235  * The hash function is meant to be lightweight as opposed to strong,
 236  * and was vaguely inspired by ppc64 firmware-supported inverted
 237  * pagetable hash functions, but uses a full hashtable full of finite
 238  * collision chains, not just pairs of them.
 239  *
 240  * -- wli
 241  */
 242 static void __profile_flip_buffers(void *unused)
 243 {
 244         int cpu = smp_processor_id();
 245
 246         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 247 }
 248
 249 static void profile_flip_buffers(void)
 250 {
 251         int i, j, cpu;
 252
 253         mutex_lock(&profile_flip_mutex);
 254         j = per_cpu(cpu_profile_flip, get_cpu());
 255         put_cpu();
 256         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 257         for_each_online_cpu(cpu) {
 258                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 259                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 260                         if (!hits[i].hits) {
 261                                 if (hits[i].pc)
 262                                         hits[i].pc = 0;
 263                                 continue;
 264                         }
 265                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 266                         hits[i].hits = hits[i].pc = 0;
 267                 }
 268         }
 269         mutex_unlock(&profile_flip_mutex);
 270 }
 271
 272 static void profile_discard_flip_buffers(void)
 273 {
 274         int i, cpu;
 275
 276         mutex_lock(&profile_flip_mutex);
 277         i = per_cpu(cpu_profile_flip, get_cpu());
 278         put_cpu();
 279         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 280         for_each_online_cpu(cpu) {
 281                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 282                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 283         }
 284         mutex_unlock(&profile_flip_mutex);
 285 }
 286
 287 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 288 {
 289         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 290         int i, j, cpu;
 291         struct profile_hit *hits;
 292
 293         if (prof_on != type || !prof_buffer)
 294                 return;
 295         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 296         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 297         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 298         cpu = get_cpu();
 299         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 300         if (!hits) {
 301                 put_cpu();
 302                 return;
 303         }
 304         /*
 305          * We buffer the global profiler buffer into a per-CPU
 306          * queue and thus reduce the number of global (and possibly
 307          * NUMA-alien) accesses. The write-queue is self-coalescing:
 308          */
 309         local_irq_save(flags);
 310         do {
 311                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 312                         if (hits[i + j].pc == pc) {
 313                                 hits[i + j].hits += nr_hits;
 314                                 goto out;
 315                         } else if (!hits[i + j].hits) {
 316                                 hits[i + j].pc = pc;
 317                                 hits[i + j].hits = nr_hits;
 318                                 goto out;
 319                         }
 320                 }
 321                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 322         } while (i != primary);
 323
 324         /*
 325          * Add the current hit(s) and flush the write-queue out
 326          * to the global buffer:
 327          */
 328         atomic_add(nr_hits, &prof_buffer[pc]);
 329         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 330                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 331                 hits[i].pc = hits[i].hits = 0;
 332         }
 333 out:
 334         local_irq_restore(flags);
 335         put_cpu();
 336 }
 337
 338 static int __devinit profile_cpu_callback(struct notifier_block *info,
 339                                         unsigned long action, void *__cpu)
 340 {
 341         int node, cpu = (unsigned long)__cpu;
 342         struct page *page;
 343
 344         switch (action) {
 345         case CPU_UP_PREPARE:
 346         case CPU_UP_PREPARE_FROZEN:
 347                 node = cpu_to_node(cpu);
 348                 per_cpu(cpu_profile_flip, cpu) = 0;
 349                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 350                         page = alloc_pages_node(node,
 351                                         GFP_KERNEL | __GFP_ZERO,
 352                                         0);
 353                         if (!page)
 354                                 return NOTIFY_BAD;
 355                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 356                 }
 357                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 358                         page = alloc_pages_node(node,
 359                                         GFP_KERNEL | __GFP_ZERO,
 360                                         0);
 361                         if (!page)
 362                                 goto out_free;
 363                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 364                 }
 365                 break;
 366 out_free:
 367                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 368                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 369                 __free_page(page);
 370                 return NOTIFY_BAD;
 371         case CPU_ONLINE:
 372         case CPU_ONLINE_FROZEN:
 373                 cpu_set(cpu, prof_cpu_mask);
 374                 break;
 375         case CPU_UP_CANCELED:
 376         case CPU_UP_CANCELED_FROZEN:
 377         case CPU_DEAD:
 378         case CPU_DEAD_FROZEN:
 379                 cpu_clear(cpu, prof_cpu_mask);
 380                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 381                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 382                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 383                         __free_page(page);
 384                 }
 385                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 386                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 387                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 388                         __free_page(page);
 389                 }
 390                 break;
 391         }
 392         return NOTIFY_OK;
 393 }
 394 #else /* !CONFIG_SMP */
 395 #define profile_flip_buffers()          do { } while (0)
 396 #define profile_discard_flip_buffers()  do { } while (0)
 397 #define profile_cpu_callback            NULL
 398
 399 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 400 {
 401         unsigned long pc;
 402
 403         if (prof_on != type || !prof_buffer)
 404                 return;
 405         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 406         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 407 }
 408 #endif /* !CONFIG_SMP */
 409 EXPORT_SYMBOL_GPL(profile_hits);
 410
 411 void profile_tick(int type)
 412 {
 413         struct pt_regs *regs = get_irq_regs();
 414
 415         if (type == CPU_PROFILING && timer_hook)
 416                 timer_hook(regs);
 417         if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
 418                 profile_hit(type, (void *)profile_pc(regs));
 419 }
 420
 421 #ifdef CONFIG_PROC_FS
 422 #include <linux/proc_fs.h>
 423 #include <asm/uaccess.h>
 424 #include <asm/ptrace.h>
 425
 426 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
 427                         int count, int *eof, void *data)
 428 {
 429         int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
 430         if (count - len < 2)
 431                 return -EINVAL;
 432         len += sprintf(page + len, "\n");
 433         return len;
 434 }
 435
 436 static int prof_cpu_mask_write_proc(struct file *file,
 437         const char __user *buffer,  unsigned long count, void *data)
 438 {
 439         cpumask_t *mask = (cpumask_t *)data;
 440         unsigned long full_count = count, err;
 441         cpumask_t new_value;
 442
 443         err = cpumask_parse_user(buffer, count, new_value);
 444         if (err)
 445                 return err;
 446
 447         *mask = new_value;
 448         return full_count;
 449 }
 450
 451 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 452 {
 453         struct proc_dir_entry *entry;
 454
 455         /* create /proc/irq/prof_cpu_mask */
 456         entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
 457         if (!entry)
 458                 return;
 459         entry->data = (void *)&prof_cpu_mask;
 460         entry->read_proc = prof_cpu_mask_read_proc;
 461         entry->write_proc = prof_cpu_mask_write_proc;
 462 }
 463
 464 /*
 465  * This function accesses profiling information. The returned data is
 466  * binary: the sampling step and the actual contents of the profile
 467  * buffer. Use of the program readprofile is recommended in order to
 468  * get meaningful info out of these data.
 469  */
 470 static ssize_t
 471 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 472 {
 473         unsigned long p = *ppos;
 474         ssize_t read;
 475         char *pnt;
 476         unsigned int sample_step = 1 << prof_shift;
 477
 478         profile_flip_buffers();
 479         if (p >= (prof_len+1)*sizeof(unsigned int))
 480                 return 0;
 481         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 482                 count = (prof_len+1)*sizeof(unsigned int) - p;
 483         read = 0;
 484
 485         while (p < sizeof(unsigned int) && count > 0) {
 486                 if (put_user(*((char *)(&sample_step)+p), buf))
 487                         return -EFAULT;
 488                 buf++; p++; count--; read++;
 489         }
 490         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 491         if (copy_to_user(buf, (void *)pnt, count))
 492                 return -EFAULT;
 493         read += count;
 494         *ppos += read;
 495         return read;
 496 }
 497
 498 /*
 499  * Writing to /proc/profile resets the counters
 500  *
 501  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 502  * interrupt frequency, on architectures that support this.
 503  */
 504 static ssize_t write_profile(struct file *file, const char __user *buf,
 505                              size_t count, loff_t *ppos)
 506 {
 507 #ifdef CONFIG_SMP
 508         extern int setup_profiling_timer(unsigned int multiplier);
 509
 510         if (count == sizeof(int)) {
 511                 unsigned int multiplier;
 512
 513                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 514                         return -EFAULT;
 515
 516                 if (setup_profiling_timer(multiplier))
 517                         return -EINVAL;
 518         }
 519 #endif
 520         profile_discard_flip_buffers();
 521         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 522         return count;
 523 }
 524
 525 static const struct file_operations proc_profile_operations = {
 526         .read           = read_profile,
 527         .write          = write_profile,
 528 };
 529
 530 #ifdef CONFIG_SMP
 531 static void __init profile_nop(void *unused)
 532 {
 533 }
 534
 535 static int __init create_hash_tables(void)
 536 {
 537         int cpu;
 538
 539         for_each_online_cpu(cpu) {
 540                 int node = cpu_to_node(cpu);
 541                 struct page *page;
 542
 543                 page = alloc_pages_node(node,
 544                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 545                                 0);
 546                 if (!page)
 547                         goto out_cleanup;
 548                 per_cpu(cpu_profile_hits, cpu)[1]
 549                                 = (struct profile_hit *)page_address(page);
 550                 page = alloc_pages_node(node,
 551                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 552                                 0);
 553                 if (!page)
 554                         goto out_cleanup;
 555                 per_cpu(cpu_profile_hits, cpu)[0]
 556                                 = (struct profile_hit *)page_address(page);
 557         }
 558         return 0;
 559 out_cleanup:
 560         prof_on = 0;
 561         smp_mb();
 562         on_each_cpu(profile_nop, NULL, 0, 1);
 563         for_each_online_cpu(cpu) {
 564                 struct page *page;
 565
 566                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 567                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 568                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 569                         __free_page(page);
 570                 }
 571                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 572                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 573                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 574                         __free_page(page);
 575                 }
 576         }
 577         return -1;
 578 }
 579 #else
 580 #define create_hash_tables()                    ({ 0; })
 581 #endif
 582
 583 static int __init create_proc_profile(void)
 584 {
 585         struct proc_dir_entry *entry;
 586
 587         if (!prof_on)
 588                 return 0;
 589         if (create_hash_tables())
 590                 return -1;
 591         entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL);
 592         if (!entry)
 593                 return 0;
 594         entry->proc_fops = &proc_profile_operations;
 595         entry->size = (1+prof_len) * sizeof(atomic_t);
 596         hotcpu_notifier(profile_cpu_callback, 0);
 597         return 0;
 598 }
 599 module_init(create_proc_profile);
 600 #endif /* CONFIG_PROC_FS */