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