kernel/profile.c

   1 /*
   2  *  linux/kernel/profile.c
   3  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   4  *  with configurable resolution, support for restricting the cpus on
   5  *  which profiling is done, and switching between cpu time and
   6  *  schedule() calls via kernel command line parameters passed at boot.
   7  *
   8  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
   9  *      Red Hat, July 2004
  10  *  Consolidation of architecture support code for profiling,
  11  *      William Irwin, Oracle, July 2004
  12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13  *      to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
  14  */
  15
  16 #include <linux/config.h>
  17 #include <linux/module.h>
  18 #include <linux/profile.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/notifier.h>
  21 #include <linux/mm.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/cpu.h>
  24 #include <linux/profile.h>
  25 #include <linux/highmem.h>
  26 #include <asm/sections.h>
  27 #include <asm/semaphore.h>
  28
  29 struct profile_hit {
  30         u32 pc, hits;
  31 };
  32 #define PROFILE_GRPSHIFT        3
  33 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  34 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  35 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  36
  37 static atomic_t *prof_buffer;
  38 static unsigned long prof_len, prof_shift;
  39 static int prof_on;
  40 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
  41 #ifdef CONFIG_SMP
  42 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  43 static DEFINE_PER_CPU(int, cpu_profile_flip);
  44 static DECLARE_MUTEX(profile_flip_mutex);
  45 #endif /* CONFIG_SMP */
  46
  47 static int __init profile_setup(char * str)
  48 {
  49         int par;
  50
  51         if (!strncmp(str, "schedule", 8)) {
  52                 prof_on = SCHED_PROFILING;
  53                 printk(KERN_INFO "kernel schedule profiling enabled\n");
  54                 if (str[7] == ',')
  55                         str += 8;
  56         }
  57         if (get_option(&str,&par)) {
  58                 prof_shift = par;
  59                 prof_on = CPU_PROFILING;
  60                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  61                         prof_shift);
  62         }
  63         return 1;
  64 }
  65 __setup("profile=", profile_setup);
  66
  67
  68 void __init profile_init(void)
  69 {
  70         if (!prof_on)
  71                 return;
  72
  73         /* only text is profiled */
  74         prof_len = (_etext - _stext) >> prof_shift;
  75         prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
  76 }
  77
  78 /* Profile event notifications */
  79
  80 #ifdef CONFIG_PROFILING
  81
  82 static DECLARE_RWSEM(profile_rwsem);
  83 static rwlock_t handoff_lock = RW_LOCK_UNLOCKED;
  84 static struct notifier_block * task_exit_notifier;
  85 static struct notifier_block * task_free_notifier;
  86 static struct notifier_block * munmap_notifier;
  87
  88 void profile_task_exit(struct task_struct * task)
  89 {
  90         down_read(&profile_rwsem);
  91         notifier_call_chain(&task_exit_notifier, 0, task);
  92         up_read(&profile_rwsem);
  93 }
  94
  95 int profile_handoff_task(struct task_struct * task)
  96 {
  97         int ret;
  98         read_lock(&handoff_lock);
  99         ret = notifier_call_chain(&task_free_notifier, 0, task);
 100         read_unlock(&handoff_lock);
 101         return (ret == NOTIFY_OK) ? 1 : 0;
 102 }
 103
 104 void profile_munmap(unsigned long addr)
 105 {
 106         down_read(&profile_rwsem);
 107         notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 108         up_read(&profile_rwsem);
 109 }
 110
 111 int task_handoff_register(struct notifier_block * n)
 112 {
 113         int err = -EINVAL;
 114
 115         write_lock(&handoff_lock);
 116         err = notifier_chain_register(&task_free_notifier, n);
 117         write_unlock(&handoff_lock);
 118         return err;
 119 }
 120
 121 int task_handoff_unregister(struct notifier_block * n)
 122 {
 123         int err = -EINVAL;
 124
 125         write_lock(&handoff_lock);
 126         err = notifier_chain_unregister(&task_free_notifier, n);
 127         write_unlock(&handoff_lock);
 128         return err;
 129 }
 130
 131 int profile_event_register(enum profile_type type, struct notifier_block * n)
 132 {
 133         int err = -EINVAL;
 134
 135         down_write(&profile_rwsem);
 136
 137         switch (type) {
 138                 case PROFILE_TASK_EXIT:
 139                         err = notifier_chain_register(&task_exit_notifier, n);
 140                         break;
 141                 case PROFILE_MUNMAP:
 142                         err = notifier_chain_register(&munmap_notifier, n);
 143                         break;
 144         }
 145
 146         up_write(&profile_rwsem);
 147
 148         return err;
 149 }
 150
 151
 152 int profile_event_unregister(enum profile_type type, struct notifier_block * n)
 153 {
 154         int err = -EINVAL;
 155
 156         down_write(&profile_rwsem);
 157
 158         switch (type) {
 159                 case PROFILE_TASK_EXIT:
 160                         err = notifier_chain_unregister(&task_exit_notifier, n);
 161                         break;
 162                 case PROFILE_MUNMAP:
 163                         err = notifier_chain_unregister(&munmap_notifier, n);
 164                         break;
 165         }
 166
 167         up_write(&profile_rwsem);
 168         return err;
 169 }
 170
 171 static struct notifier_block * profile_listeners;
 172 static rwlock_t profile_lock = RW_LOCK_UNLOCKED;
 173
 174 int register_profile_notifier(struct notifier_block * nb)
 175 {
 176         int err;
 177         write_lock_irq(&profile_lock);
 178         err = notifier_chain_register(&profile_listeners, nb);
 179         write_unlock_irq(&profile_lock);
 180         return err;
 181 }
 182
 183
 184 int unregister_profile_notifier(struct notifier_block * nb)
 185 {
 186         int err;
 187         write_lock_irq(&profile_lock);
 188         err = notifier_chain_unregister(&profile_listeners, nb);
 189         write_unlock_irq(&profile_lock);
 190         return err;
 191 }
 192
 193
 194 void profile_hook(struct pt_regs * regs)
 195 {
 196         read_lock(&profile_lock);
 197         notifier_call_chain(&profile_listeners, 0, regs);
 198         read_unlock(&profile_lock);
 199 }
 200
 201 EXPORT_SYMBOL_GPL(register_profile_notifier);
 202 EXPORT_SYMBOL_GPL(unregister_profile_notifier);
 203 EXPORT_SYMBOL_GPL(task_handoff_register);
 204 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 205
 206 #endif /* CONFIG_PROFILING */
 207
 208 EXPORT_SYMBOL_GPL(profile_event_register);
 209 EXPORT_SYMBOL_GPL(profile_event_unregister);
 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 profile_hit() may be called from 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         down(&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         up(&profile_flip_mutex);
 270 }
 271
 272 static void profile_discard_flip_buffers(void)
 273 {
 274         int i, cpu;
 275
 276         down(&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         up(&profile_flip_mutex);
 285 }
 286
 287 void profile_hit(int type, void *__pc)
 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         local_irq_save(flags);
 305         do {
 306                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 307                         if (hits[i + j].pc == pc) {
 308                                 hits[i + j].hits++;
 309                                 goto out;
 310                         } else if (!hits[i + j].hits) {
 311                                 hits[i + j].pc = pc;
 312                                 hits[i + j].hits = 1;
 313                                 goto out;
 314                         }
 315                 }
 316                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 317         } while (i != primary);
 318         atomic_inc(&prof_buffer[pc]);
 319         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 320                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 321                 hits[i].pc = hits[i].hits = 0;
 322         }
 323 out:
 324         local_irq_restore(flags);
 325         put_cpu();
 326 }
 327
 328 #ifdef CONFIG_HOTPLUG_CPU
 329 static int __devinit profile_cpu_callback(struct notifier_block *info,
 330                                         unsigned long action, void *__cpu)
 331 {
 332         int node, cpu = (unsigned long)__cpu;
 333         struct page *page;
 334
 335         switch (action) {
 336         case CPU_UP_PREPARE:
 337                 node = cpu_to_node(cpu);
 338                 per_cpu(cpu_profile_flip, cpu) = 0;
 339                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 340                         page = alloc_pages_node(node, GFP_KERNEL, 0);
 341                         if (!page)
 342                                 return NOTIFY_BAD;
 343                         clear_highpage(page);
 344                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 345                 }
 346                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 347                         page = alloc_pages_node(node, GFP_KERNEL, 0);
 348                         if (!page)
 349                                 goto out_free;
 350                         clear_highpage(page);
 351                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 352                 }
 353                 break;
 354         out_free:
 355                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 356                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 357                 __free_page(page);
 358                 return NOTIFY_BAD;
 359         case CPU_ONLINE:
 360                 cpu_set(cpu, prof_cpu_mask);
 361                 break;
 362         case CPU_UP_CANCELED:
 363         case CPU_DEAD:
 364                 cpu_clear(cpu, prof_cpu_mask);
 365                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 366                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 367                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 368                         __free_page(page);
 369                 }
 370                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 371                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 372                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 373                         __free_page(page);
 374                 }
 375                 break;
 376         }
 377         return NOTIFY_OK;
 378 }
 379 #endif /* CONFIG_HOTPLUG_CPU */
 380 #else /* !CONFIG_SMP */
 381 #define profile_flip_buffers()          do { } while (0)
 382 #define profile_discard_flip_buffers()  do { } while (0)
 383
 384 void profile_hit(int type, void *__pc)
 385 {
 386         unsigned long pc;
 387
 388         if (prof_on != type || !prof_buffer)
 389                 return;
 390         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 391         atomic_inc(&prof_buffer[min(pc, prof_len - 1)]);
 392 }
 393 #endif /* !CONFIG_SMP */
 394
 395 void profile_tick(int type, struct pt_regs *regs)
 396 {
 397         if (type == CPU_PROFILING)
 398                 profile_hook(regs);
 399         if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask))
 400                 profile_hit(type, (void *)profile_pc(regs));
 401 }
 402
 403 #ifdef CONFIG_PROC_FS
 404 #include <linux/proc_fs.h>
 405 #include <asm/uaccess.h>
 406 #include <asm/ptrace.h>
 407
 408 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
 409                         int count, int *eof, void *data)
 410 {
 411         int len = cpumask_scnprintf(page, count, *(cpumask_t *)data);
 412         if (count - len < 2)
 413                 return -EINVAL;
 414         len += sprintf(page + len, "\n");
 415         return len;
 416 }
 417
 418 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer,
 419                                         unsigned long count, void *data)
 420 {
 421         cpumask_t *mask = (cpumask_t *)data;
 422         unsigned long full_count = count, err;
 423         cpumask_t new_value;
 424
 425         err = cpumask_parse(buffer, count, new_value);
 426         if (err)
 427                 return err;
 428
 429         *mask = new_value;
 430         return full_count;
 431 }
 432
 433 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 434 {
 435         struct proc_dir_entry *entry;
 436
 437         /* create /proc/irq/prof_cpu_mask */
 438         if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir)))
 439                 return;
 440         entry->nlink = 1;
 441         entry->data = (void *)&prof_cpu_mask;
 442         entry->read_proc = prof_cpu_mask_read_proc;
 443         entry->write_proc = prof_cpu_mask_write_proc;
 444 }
 445
 446 /*
 447  * This function accesses profiling information. The returned data is
 448  * binary: the sampling step and the actual contents of the profile
 449  * buffer. Use of the program readprofile is recommended in order to
 450  * get meaningful info out of these data.
 451  */
 452 static ssize_t
 453 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 454 {
 455         unsigned long p = *ppos;
 456         ssize_t read;
 457         char * pnt;
 458         unsigned int sample_step = 1 << prof_shift;
 459
 460         profile_flip_buffers();
 461         if (p >= (prof_len+1)*sizeof(unsigned int))
 462                 return 0;
 463         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 464                 count = (prof_len+1)*sizeof(unsigned int) - p;
 465         read = 0;
 466
 467         while (p < sizeof(unsigned int) && count > 0) {
 468                 put_user(*((char *)(&sample_step)+p),buf);
 469                 buf++; p++; count--; read++;
 470         }
 471         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 472         if (copy_to_user(buf,(void *)pnt,count))
 473                 return -EFAULT;
 474         read += count;
 475         *ppos += read;
 476         return read;
 477 }
 478
 479 /*
 480  * Writing to /proc/profile resets the counters
 481  *
 482  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 483  * interrupt frequency, on architectures that support this.
 484  */
 485 static ssize_t write_profile(struct file *file, const char __user *buf,
 486                              size_t count, loff_t *ppos)
 487 {
 488 #ifdef CONFIG_SMP
 489         extern int setup_profiling_timer (unsigned int multiplier);
 490
 491         if (count == sizeof(int)) {
 492                 unsigned int multiplier;
 493
 494                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 495                         return -EFAULT;
 496
 497                 if (setup_profiling_timer(multiplier))
 498                         return -EINVAL;
 499         }
 500 #endif
 501         profile_discard_flip_buffers();
 502         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 503         return count;
 504 }
 505
 506 static struct file_operations proc_profile_operations = {
 507         .read           = read_profile,
 508         .write          = write_profile,
 509 };
 510
 511 #ifdef CONFIG_SMP
 512 static void __init profile_nop(void *unused)
 513 {
 514 }
 515
 516 static int __init create_hash_tables(void)
 517 {
 518         int cpu;
 519
 520         for_each_online_cpu(cpu) {
 521                 int node = cpu_to_node(cpu);
 522                 struct page *page;
 523
 524                 page = alloc_pages_node(node, GFP_KERNEL, 0);
 525                 if (!page)
 526                         goto out_cleanup;
 527                 clear_highpage(page);
 528                 per_cpu(cpu_profile_hits, cpu)[1]
 529                                 = (struct profile_hit *)page_address(page);
 530                 page = alloc_pages_node(node, GFP_KERNEL, 0);
 531                 if (!page)
 532                         goto out_cleanup;
 533                 clear_highpage(page);
 534                 per_cpu(cpu_profile_hits, cpu)[0]
 535                                 = (struct profile_hit *)page_address(page);
 536         }
 537         return 0;
 538 out_cleanup:
 539         prof_on = 0;
 540         mb();
 541         on_each_cpu(profile_nop, NULL, 0, 1);
 542         for_each_online_cpu(cpu) {
 543                 struct page *page;
 544
 545                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 546                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 547                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 548                         __free_page(page);
 549                 }
 550                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 551                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 552                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 553                         __free_page(page);
 554                 }
 555         }
 556         return -1;
 557 }
 558 #else
 559 #define create_hash_tables()                    ({ 0; })
 560 #endif
 561
 562 static int __init create_proc_profile(void)
 563 {
 564         struct proc_dir_entry *entry;
 565
 566         if (!prof_on)
 567                 return 0;
 568         if (create_hash_tables())
 569                 return -1;
 570         if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL)))
 571                 return 0;
 572         entry->proc_fops = &proc_profile_operations;
 573         entry->size = (1+prof_len) * sizeof(atomic_t);
 574         hotcpu_notifier(profile_cpu_callback, 0);
 575         return 0;
 576 }
 577 module_init(create_proc_profile);
 578 #endif /* CONFIG_PROC_FS */