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