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/highmem.h>
  24 #include <linux/mutex.h>
  25 #include <asm/sections.h>
  26 #include <asm/irq_regs.h>
  27 #include <asm/ptrace.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 static int (*timer_hook)(struct pt_regs *) __read_mostly;
  39
  40 static atomic_t *prof_buffer;
  41 static unsigned long prof_len, prof_shift;
  42
  43 int prof_on __read_mostly;
  44 EXPORT_SYMBOL_GPL(prof_on);
  45
  46 static cpumask_t prof_cpu_mask = CPU_MASK_ALL;
  47 #ifdef CONFIG_SMP
  48 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  49 static DEFINE_PER_CPU(int, cpu_profile_flip);
  50 static DEFINE_MUTEX(profile_flip_mutex);
  51 #endif /* CONFIG_SMP */
  52
  53 static int __init profile_setup(char *str)
  54 {
  55         static char __initdata schedstr[] = "schedule";
  56         static char __initdata sleepstr[] = "sleep";
  57         static char __initdata kvmstr[] = "kvm";
  58         int par;
  59
  60         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  61 #ifdef CONFIG_SCHEDSTATS
  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
  71                 printk(KERN_WARNING
  72                         "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  73 #endif /* CONFIG_SCHEDSTATS */
  74         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  75                 prof_on = SCHED_PROFILING;
  76                 if (str[strlen(schedstr)] == ',')
  77                         str += strlen(schedstr) + 1;
  78                 if (get_option(&str, &par))
  79                         prof_shift = par;
  80                 printk(KERN_INFO
  81                         "kernel schedule profiling enabled (shift: %ld)\n",
  82                         prof_shift);
  83         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  84                 prof_on = KVM_PROFILING;
  85                 if (str[strlen(kvmstr)] == ',')
  86                         str += strlen(kvmstr) + 1;
  87                 if (get_option(&str, &par))
  88                         prof_shift = par;
  89                 printk(KERN_INFO
  90                         "kernel KVM profiling enabled (shift: %ld)\n",
  91                         prof_shift);
  92         } else if (get_option(&str, &par)) {
  93                 prof_shift = par;
  94                 prof_on = CPU_PROFILING;
  95                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  96                         prof_shift);
  97         }
  98         return 1;
  99 }
 100 __setup("profile=", profile_setup);
 101
 102
 103 void __init profile_init(void)
 104 {
 105         if (!prof_on)
 106                 return;
 107
 108         /* only text is profiled */
 109         prof_len = (_etext - _stext) >> prof_shift;
 110         prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t));
 111 }
 112
 113 /* Profile event notifications */
 114
 115 #ifdef CONFIG_PROFILING
 116
 117 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 118 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 119 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 120
 121 void profile_task_exit(struct task_struct *task)
 122 {
 123         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 124 }
 125
 126 int profile_handoff_task(struct task_struct *task)
 127 {
 128         int ret;
 129         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 130         return (ret == NOTIFY_OK) ? 1 : 0;
 131 }
 132
 133 void profile_munmap(unsigned long addr)
 134 {
 135         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 136 }
 137
 138 int task_handoff_register(struct notifier_block *n)
 139 {
 140         return atomic_notifier_chain_register(&task_free_notifier, n);
 141 }
 142 EXPORT_SYMBOL_GPL(task_handoff_register);
 143
 144 int task_handoff_unregister(struct notifier_block *n)
 145 {
 146         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 147 }
 148 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 149
 150 int profile_event_register(enum profile_type type, struct notifier_block *n)
 151 {
 152         int err = -EINVAL;
 153
 154         switch (type) {
 155         case PROFILE_TASK_EXIT:
 156                 err = blocking_notifier_chain_register(
 157                                 &task_exit_notifier, n);
 158                 break;
 159         case PROFILE_MUNMAP:
 160                 err = blocking_notifier_chain_register(
 161                                 &munmap_notifier, n);
 162                 break;
 163         }
 164
 165         return err;
 166 }
 167 EXPORT_SYMBOL_GPL(profile_event_register);
 168
 169 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 170 {
 171         int err = -EINVAL;
 172
 173         switch (type) {
 174         case PROFILE_TASK_EXIT:
 175                 err = blocking_notifier_chain_unregister(
 176                                 &task_exit_notifier, n);
 177                 break;
 178         case PROFILE_MUNMAP:
 179                 err = blocking_notifier_chain_unregister(
 180                                 &munmap_notifier, n);
 181                 break;
 182         }
 183
 184         return err;
 185 }
 186 EXPORT_SYMBOL_GPL(profile_event_unregister);
 187
 188 int register_timer_hook(int (*hook)(struct pt_regs *))
 189 {
 190         if (timer_hook)
 191                 return -EBUSY;
 192         timer_hook = hook;
 193         return 0;
 194 }
 195 EXPORT_SYMBOL_GPL(register_timer_hook);
 196
 197 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 198 {
 199         WARN_ON(hook != timer_hook);
 200         timer_hook = NULL;
 201         /* make sure all CPUs see the NULL hook */
 202         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 203 }
 204 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 205
 206 #endif /* CONFIG_PROFILING */
 207
 208
 209 #ifdef CONFIG_SMP
 210 /*
 211  * Each cpu has a pair of open-addressed hashtables for pending
 212  * profile hits. read_profile() IPI's all cpus to request them
 213  * to flip buffers and flushes their contents to prof_buffer itself.
 214  * Flip requests are serialized by the profile_flip_mutex. The sole
 215  * use of having a second hashtable is for avoiding cacheline
 216  * contention that would otherwise happen during flushes of pending
 217  * profile hits required for the accuracy of reported profile hits
 218  * and so resurrect the interrupt livelock issue.
 219  *
 220  * The open-addressed hashtables are indexed by profile buffer slot
 221  * and hold the number of pending hits to that profile buffer slot on
 222  * a cpu in an entry. When the hashtable overflows, all pending hits
 223  * are accounted to their corresponding profile buffer slots with
 224  * atomic_add() and the hashtable emptied. As numerous pending hits
 225  * may be accounted to a profile buffer slot in a hashtable entry,
 226  * this amortizes a number of atomic profile buffer increments likely
 227  * to be far larger than the number of entries in the hashtable,
 228  * particularly given that the number of distinct profile buffer
 229  * positions to which hits are accounted during short intervals (e.g.
 230  * several seconds) is usually very small. Exclusion from buffer
 231  * flipping is provided by interrupt disablement (note that for
 232  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 233  * process context).
 234  * The hash function is meant to be lightweight as opposed to strong,
 235  * and was vaguely inspired by ppc64 firmware-supported inverted
 236  * pagetable hash functions, but uses a full hashtable full of finite
 237  * collision chains, not just pairs of them.
 238  *
 239  * -- wli
 240  */
 241 static void __profile_flip_buffers(void *unused)
 242 {
 243         int cpu = smp_processor_id();
 244
 245         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 246 }
 247
 248 static void profile_flip_buffers(void)
 249 {
 250         int i, j, cpu;
 251
 252         mutex_lock(&profile_flip_mutex);
 253         j = per_cpu(cpu_profile_flip, get_cpu());
 254         put_cpu();
 255         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 256         for_each_online_cpu(cpu) {
 257                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 258                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 259                         if (!hits[i].hits) {
 260                                 if (hits[i].pc)
 261                                         hits[i].pc = 0;
 262                                 continue;
 263                         }
 264                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 265                         hits[i].hits = hits[i].pc = 0;
 266                 }
 267         }
 268         mutex_unlock(&profile_flip_mutex);
 269 }
 270
 271 static void profile_discard_flip_buffers(void)
 272 {
 273         int i, cpu;
 274
 275         mutex_lock(&profile_flip_mutex);
 276         i = per_cpu(cpu_profile_flip, get_cpu());
 277         put_cpu();
 278         on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
 279         for_each_online_cpu(cpu) {
 280                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 281                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 282         }
 283         mutex_unlock(&profile_flip_mutex);
 284 }
 285
 286 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 287 {
 288         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 289         int i, j, cpu;
 290         struct profile_hit *hits;
 291
 292         if (prof_on != type || !prof_buffer)
 293                 return;
 294         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 295         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 296         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 297         cpu = get_cpu();
 298         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 299         if (!hits) {
 300                 put_cpu();
 301                 return;
 302         }
 303         /*
 304          * We buffer the global profiler buffer into a per-CPU
 305          * queue and thus reduce the number of global (and possibly
 306          * NUMA-alien) accesses. The write-queue is self-coalescing:
 307          */
 308         local_irq_save(flags);
 309         do {
 310                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 311                         if (hits[i + j].pc == pc) {
 312                                 hits[i + j].hits += nr_hits;
 313                                 goto out;
 314                         } else if (!hits[i + j].hits) {
 315                                 hits[i + j].pc = pc;
 316                                 hits[i + j].hits = nr_hits;
 317                                 goto out;
 318                         }
 319                 }
 320                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 321         } while (i != primary);
 322
 323         /*
 324          * Add the current hit(s) and flush the write-queue out
 325          * to the global buffer:
 326          */
 327         atomic_add(nr_hits, &prof_buffer[pc]);
 328         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 329                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 330                 hits[i].pc = hits[i].hits = 0;
 331         }
 332 out:
 333         local_irq_restore(flags);
 334         put_cpu();
 335 }
 336
 337 static int __devinit profile_cpu_callback(struct notifier_block *info,
 338                                         unsigned long action, void *__cpu)
 339 {
 340         int node, cpu = (unsigned long)__cpu;
 341         struct page *page;
 342
 343         switch (action) {
 344         case CPU_UP_PREPARE:
 345         case CPU_UP_PREPARE_FROZEN:
 346                 node = cpu_to_node(cpu);
 347                 per_cpu(cpu_profile_flip, cpu) = 0;
 348                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 349                         page = alloc_pages_node(node,
 350                                         GFP_KERNEL | __GFP_ZERO,
 351                                         0);
 352                         if (!page)
 353                                 return NOTIFY_BAD;
 354                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 355                 }
 356                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 357                         page = alloc_pages_node(node,
 358                                         GFP_KERNEL | __GFP_ZERO,
 359                                         0);
 360                         if (!page)
 361                                 goto out_free;
 362                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 363                 }
 364                 break;
 365 out_free:
 366                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 367                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 368                 __free_page(page);
 369                 return NOTIFY_BAD;
 370         case CPU_ONLINE:
 371         case CPU_ONLINE_FROZEN:
 372                 cpu_set(cpu, prof_cpu_mask);
 373                 break;
 374         case CPU_UP_CANCELED:
 375         case CPU_UP_CANCELED_FROZEN:
 376         case CPU_DEAD:
 377         case CPU_DEAD_FROZEN:
 378                 cpu_clear(cpu, prof_cpu_mask);
 379                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 380                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 381                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 382                         __free_page(page);
 383                 }
 384                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 385                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 386                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 387                         __free_page(page);
 388                 }
 389                 break;
 390         }
 391         return NOTIFY_OK;
 392 }
 393 #else /* !CONFIG_SMP */
 394 #define profile_flip_buffers()          do { } while (0)
 395 #define profile_discard_flip_buffers()  do { } while (0)
 396 #define profile_cpu_callback            NULL
 397
 398 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 399 {
 400         unsigned long pc;
 401
 402         if (prof_on != type || !prof_buffer)
 403                 return;
 404         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 405         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 406 }
 407 #endif /* !CONFIG_SMP */
 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,
 436         const char __user *buffer,  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         entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
 456         if (!entry)
 457                 return;
 458         entry->data = (void *)&prof_cpu_mask;
 459         entry->read_proc = prof_cpu_mask_read_proc;
 460         entry->write_proc = prof_cpu_mask_write_proc;
 461 }
 462
 463 /*
 464  * This function accesses profiling information. The returned data is
 465  * binary: the sampling step and the actual contents of the profile
 466  * buffer. Use of the program readprofile is recommended in order to
 467  * get meaningful info out of these data.
 468  */
 469 static ssize_t
 470 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 471 {
 472         unsigned long p = *ppos;
 473         ssize_t read;
 474         char *pnt;
 475         unsigned int sample_step = 1 << prof_shift;
 476
 477         profile_flip_buffers();
 478         if (p >= (prof_len+1)*sizeof(unsigned int))
 479                 return 0;
 480         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 481                 count = (prof_len+1)*sizeof(unsigned int) - p;
 482         read = 0;
 483
 484         while (p < sizeof(unsigned int) && count > 0) {
 485                 if (put_user(*((char *)(&sample_step)+p), buf))
 486                         return -EFAULT;
 487                 buf++; p++; count--; read++;
 488         }
 489         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 490         if (copy_to_user(buf, (void *)pnt, count))
 491                 return -EFAULT;
 492         read += count;
 493         *ppos += read;
 494         return read;
 495 }
 496
 497 /*
 498  * Writing to /proc/profile resets the counters
 499  *
 500  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 501  * interrupt frequency, on architectures that support this.
 502  */
 503 static ssize_t write_profile(struct file *file, const char __user *buf,
 504                              size_t count, loff_t *ppos)
 505 {
 506 #ifdef CONFIG_SMP
 507         extern int setup_profiling_timer(unsigned int multiplier);
 508
 509         if (count == sizeof(int)) {
 510                 unsigned int multiplier;
 511
 512                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 513                         return -EFAULT;
 514
 515                 if (setup_profiling_timer(multiplier))
 516                         return -EINVAL;
 517         }
 518 #endif
 519         profile_discard_flip_buffers();
 520         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 521         return count;
 522 }
 523
 524 static const struct file_operations proc_profile_operations = {
 525         .read           = read_profile,
 526         .write          = write_profile,
 527 };
 528
 529 #ifdef CONFIG_SMP
 530 static void __init profile_nop(void *unused)
 531 {
 532 }
 533
 534 static int __init create_hash_tables(void)
 535 {
 536         int cpu;
 537
 538         for_each_online_cpu(cpu) {
 539                 int node = cpu_to_node(cpu);
 540                 struct page *page;
 541
 542                 page = alloc_pages_node(node,
 543                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 544                                 0);
 545                 if (!page)
 546                         goto out_cleanup;
 547                 per_cpu(cpu_profile_hits, cpu)[1]
 548                                 = (struct profile_hit *)page_address(page);
 549                 page = alloc_pages_node(node,
 550                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 551                                 0);
 552                 if (!page)
 553                         goto out_cleanup;
 554                 per_cpu(cpu_profile_hits, cpu)[0]
 555                                 = (struct profile_hit *)page_address(page);
 556         }
 557         return 0;
 558 out_cleanup:
 559         prof_on = 0;
 560         smp_mb();
 561         on_each_cpu(profile_nop, NULL, 0, 1);
 562         for_each_online_cpu(cpu) {
 563                 struct page *page;
 564
 565                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 566                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 567                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 568                         __free_page(page);
 569                 }
 570                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 571                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 572                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 573                         __free_page(page);
 574                 }
 575         }
 576         return -1;
 577 }
 578 #else
 579 #define create_hash_tables()                    ({ 0; })
 580 #endif
 581
 582 static int __init create_proc_profile(void)
 583 {
 584         struct proc_dir_entry *entry;
 585
 586         if (!prof_on)
 587                 return 0;
 588         if (create_hash_tables())
 589                 return -1;
 590         entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL);
 591         if (!entry)
 592                 return 0;
 593         entry->proc_fops = &proc_profile_operations;
 594         entry->size = (1+prof_len) * sizeof(atomic_t);
 595         hotcpu_notifier(profile_cpu_callback, 0);
 596         return 0;
 597 }
 598 module_init(create_proc_profile);
 599 #endif /* CONFIG_PROC_FS */