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