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