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  *      Nadia Yvette Chambers, Oracle, July 2004
  12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13  *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  14  *      Oracle, 2004
  15  */
  16
  17 #include <linux/export.h>
  18 #include <linux/profile.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/notifier.h>
  21 #include <linux/mm.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/cpu.h>
  24 #include <linux/highmem.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include <linux/vmalloc.h>
  28 #include <asm/sections.h>
  29 #include <asm/irq_regs.h>
  30 #include <asm/ptrace.h>
  31
  32 struct profile_hit {
  33         u32 pc, hits;
  34 };
  35 #define PROFILE_GRPSHIFT        3
  36 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  37 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  38 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  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_var_t prof_cpu_mask;
  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 int profile_setup(char *str)
  54 {
  55         static char schedstr[] = "schedule";
  56         static char sleepstr[] = "sleep";
  57         static char 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 int __ref profile_init(void)
 104 {
 105         int buffer_bytes;
 106         if (!prof_on)
 107                 return 0;
 108
 109         /* only text is profiled */
 110         prof_len = (_etext - _stext) >> prof_shift;
 111         buffer_bytes = prof_len*sizeof(atomic_t);
 112
 113         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 114                 return -ENOMEM;
 115
 116         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 117
 118         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 119         if (prof_buffer)
 120                 return 0;
 121
 122         prof_buffer = alloc_pages_exact(buffer_bytes,
 123                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 124         if (prof_buffer)
 125                 return 0;
 126
 127         prof_buffer = vzalloc(buffer_bytes);
 128         if (prof_buffer)
 129                 return 0;
 130
 131         free_cpumask_var(prof_cpu_mask);
 132         return -ENOMEM;
 133 }
 134
 135 /* Profile event notifications */
 136
 137 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 138 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 139 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 140
 141 void profile_task_exit(struct task_struct *task)
 142 {
 143         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 144 }
 145
 146 int profile_handoff_task(struct task_struct *task)
 147 {
 148         int ret;
 149         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 150         return (ret == NOTIFY_OK) ? 1 : 0;
 151 }
 152
 153 void profile_munmap(unsigned long addr)
 154 {
 155         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 156 }
 157
 158 int task_handoff_register(struct notifier_block *n)
 159 {
 160         return atomic_notifier_chain_register(&task_free_notifier, n);
 161 }
 162 EXPORT_SYMBOL_GPL(task_handoff_register);
 163
 164 int task_handoff_unregister(struct notifier_block *n)
 165 {
 166         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 167 }
 168 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 169
 170 int profile_event_register(enum profile_type type, struct notifier_block *n)
 171 {
 172         int err = -EINVAL;
 173
 174         switch (type) {
 175         case PROFILE_TASK_EXIT:
 176                 err = blocking_notifier_chain_register(
 177                                 &task_exit_notifier, n);
 178                 break;
 179         case PROFILE_MUNMAP:
 180                 err = blocking_notifier_chain_register(
 181                                 &munmap_notifier, n);
 182                 break;
 183         }
 184
 185         return err;
 186 }
 187 EXPORT_SYMBOL_GPL(profile_event_register);
 188
 189 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 190 {
 191         int err = -EINVAL;
 192
 193         switch (type) {
 194         case PROFILE_TASK_EXIT:
 195                 err = blocking_notifier_chain_unregister(
 196                                 &task_exit_notifier, n);
 197                 break;
 198         case PROFILE_MUNMAP:
 199                 err = blocking_notifier_chain_unregister(
 200                                 &munmap_notifier, n);
 201                 break;
 202         }
 203
 204         return err;
 205 }
 206 EXPORT_SYMBOL_GPL(profile_event_unregister);
 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  * -- nyc
 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, 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, 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 static void do_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         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 292         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 293         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 294         cpu = get_cpu();
 295         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 296         if (!hits) {
 297                 put_cpu();
 298                 return;
 299         }
 300         /*
 301          * We buffer the global profiler buffer into a per-CPU
 302          * queue and thus reduce the number of global (and possibly
 303          * NUMA-alien) accesses. The write-queue is self-coalescing:
 304          */
 305         local_irq_save(flags);
 306         do {
 307                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 308                         if (hits[i + j].pc == pc) {
 309                                 hits[i + j].hits += nr_hits;
 310                                 goto out;
 311                         } else if (!hits[i + j].hits) {
 312                                 hits[i + j].pc = pc;
 313                                 hits[i + j].hits = nr_hits;
 314                                 goto out;
 315                         }
 316                 }
 317                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 318         } while (i != primary);
 319
 320         /*
 321          * Add the current hit(s) and flush the write-queue out
 322          * to the global buffer:
 323          */
 324         atomic_add(nr_hits, &prof_buffer[pc]);
 325         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 326                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 327                 hits[i].pc = hits[i].hits = 0;
 328         }
 329 out:
 330         local_irq_restore(flags);
 331         put_cpu();
 332 }
 333
 334 static int profile_cpu_callback(struct notifier_block *info,
 335                                         unsigned long action, void *__cpu)
 336 {
 337         int node, cpu = (unsigned long)__cpu;
 338         struct page *page;
 339
 340         switch (action) {
 341         case CPU_UP_PREPARE:
 342         case CPU_UP_PREPARE_FROZEN:
 343                 node = cpu_to_mem(cpu);
 344                 per_cpu(cpu_profile_flip, cpu) = 0;
 345                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 346                         page = alloc_pages_exact_node(node,
 347                                         GFP_KERNEL | __GFP_ZERO,
 348                                         0);
 349                         if (!page)
 350                                 return notifier_from_errno(-ENOMEM);
 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_exact_node(node,
 355                                         GFP_KERNEL | __GFP_ZERO,
 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 notifier_from_errno(-ENOMEM);
 367         case CPU_ONLINE:
 368         case CPU_ONLINE_FROZEN:
 369                 if (prof_cpu_mask != NULL)
 370                         cpumask_set_cpu(cpu, prof_cpu_mask);
 371                 break;
 372         case CPU_UP_CANCELED:
 373         case CPU_UP_CANCELED_FROZEN:
 374         case CPU_DEAD:
 375         case CPU_DEAD_FROZEN:
 376                 if (prof_cpu_mask != NULL)
 377                         cpumask_clear_cpu(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 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 398 {
 399         unsigned long pc;
 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
 405 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 406 {
 407         if (prof_on != type || !prof_buffer)
 408                 return;
 409         do_profile_hits(type, __pc, nr_hits);
 410 }
 411 EXPORT_SYMBOL_GPL(profile_hits);
 412
 413 void profile_tick(int type)
 414 {
 415         struct pt_regs *regs = get_irq_regs();
 416
 417         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 418             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 419                 profile_hit(type, (void *)profile_pc(regs));
 420 }
 421
 422 #ifdef CONFIG_PROC_FS
 423 #include <linux/proc_fs.h>
 424 #include <linux/seq_file.h>
 425 #include <asm/uaccess.h>
 426
 427 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 428 {
 429         seq_cpumask(m, prof_cpu_mask);
 430         seq_putc(m, '\n');
 431         return 0;
 432 }
 433
 434 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 435 {
 436         return single_open(file, prof_cpu_mask_proc_show, NULL);
 437 }
 438
 439 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 440         const char __user *buffer, size_t count, loff_t *pos)
 441 {
 442         cpumask_var_t new_value;
 443         int err;
 444
 445         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 446                 return -ENOMEM;
 447
 448         err = cpumask_parse_user(buffer, count, new_value);
 449         if (!err) {
 450                 cpumask_copy(prof_cpu_mask, new_value);
 451                 err = count;
 452         }
 453         free_cpumask_var(new_value);
 454         return err;
 455 }
 456
 457 static const struct file_operations prof_cpu_mask_proc_fops = {
 458         .open           = prof_cpu_mask_proc_open,
 459         .read           = seq_read,
 460         .llseek         = seq_lseek,
 461         .release        = single_release,
 462         .write          = prof_cpu_mask_proc_write,
 463 };
 464
 465 void create_prof_cpu_mask(void)
 466 {
 467         /* create /proc/irq/prof_cpu_mask */
 468         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 469 }
 470
 471 /*
 472  * This function accesses profiling information. The returned data is
 473  * binary: the sampling step and the actual contents of the profile
 474  * buffer. Use of the program readprofile is recommended in order to
 475  * get meaningful info out of these data.
 476  */
 477 static ssize_t
 478 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 479 {
 480         unsigned long p = *ppos;
 481         ssize_t read;
 482         char *pnt;
 483         unsigned int sample_step = 1 << prof_shift;
 484
 485         profile_flip_buffers();
 486         if (p >= (prof_len+1)*sizeof(unsigned int))
 487                 return 0;
 488         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 489                 count = (prof_len+1)*sizeof(unsigned int) - p;
 490         read = 0;
 491
 492         while (p < sizeof(unsigned int) && count > 0) {
 493                 if (put_user(*((char *)(&sample_step)+p), buf))
 494                         return -EFAULT;
 495                 buf++; p++; count--; read++;
 496         }
 497         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 498         if (copy_to_user(buf, (void *)pnt, count))
 499                 return -EFAULT;
 500         read += count;
 501         *ppos += read;
 502         return read;
 503 }
 504
 505 /*
 506  * Writing to /proc/profile resets the counters
 507  *
 508  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 509  * interrupt frequency, on architectures that support this.
 510  */
 511 static ssize_t write_profile(struct file *file, const char __user *buf,
 512                              size_t count, loff_t *ppos)
 513 {
 514 #ifdef CONFIG_SMP
 515         extern int setup_profiling_timer(unsigned int multiplier);
 516
 517         if (count == sizeof(int)) {
 518                 unsigned int multiplier;
 519
 520                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 521                         return -EFAULT;
 522
 523                 if (setup_profiling_timer(multiplier))
 524                         return -EINVAL;
 525         }
 526 #endif
 527         profile_discard_flip_buffers();
 528         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 529         return count;
 530 }
 531
 532 static const struct file_operations proc_profile_operations = {
 533         .read           = read_profile,
 534         .write          = write_profile,
 535         .llseek         = default_llseek,
 536 };
 537
 538 #ifdef CONFIG_SMP
 539 static void profile_nop(void *unused)
 540 {
 541 }
 542
 543 static int create_hash_tables(void)
 544 {
 545         int cpu;
 546
 547         for_each_online_cpu(cpu) {
 548                 int node = cpu_to_mem(cpu);
 549                 struct page *page;
 550
 551                 page = alloc_pages_exact_node(node,
 552                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 553                                 0);
 554                 if (!page)
 555                         goto out_cleanup;
 556                 per_cpu(cpu_profile_hits, cpu)[1]
 557                                 = (struct profile_hit *)page_address(page);
 558                 page = alloc_pages_exact_node(node,
 559                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 560                                 0);
 561                 if (!page)
 562                         goto out_cleanup;
 563                 per_cpu(cpu_profile_hits, cpu)[0]
 564                                 = (struct profile_hit *)page_address(page);
 565         }
 566         return 0;
 567 out_cleanup:
 568         prof_on = 0;
 569         smp_mb();
 570         on_each_cpu(profile_nop, NULL, 1);
 571         for_each_online_cpu(cpu) {
 572                 struct page *page;
 573
 574                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 575                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 576                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 577                         __free_page(page);
 578                 }
 579                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 580                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 581                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 582                         __free_page(page);
 583                 }
 584         }
 585         return -1;
 586 }
 587 #else
 588 #define create_hash_tables()                    ({ 0; })
 589 #endif
 590
 591 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 592 {
 593         struct proc_dir_entry *entry;
 594
 595         if (!prof_on)
 596                 return 0;
 597         if (create_hash_tables())
 598                 return -ENOMEM;
 599         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 600                             NULL, &proc_profile_operations);
 601         if (!entry)
 602                 return 0;
 603         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 604         hotcpu_notifier(profile_cpu_callback, 0);
 605         return 0;
 606 }
 607 module_init(create_proc_profile);
 608 #endif /* CONFIG_PROC_FS */