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