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 const char schedstr[] = "schedule";
  56         static const char sleepstr[] = "sleep";
  57         static const 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                 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
  68                         prof_shift);
  69 #else
  70                 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  71 #endif /* CONFIG_SCHEDSTATS */
  72         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  73                 prof_on = SCHED_PROFILING;
  74                 if (str[strlen(schedstr)] == ',')
  75                         str += strlen(schedstr) + 1;
  76                 if (get_option(&str, &par))
  77                         prof_shift = par;
  78                 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
  79                         prof_shift);
  80         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  81                 prof_on = KVM_PROFILING;
  82                 if (str[strlen(kvmstr)] == ',')
  83                         str += strlen(kvmstr) + 1;
  84                 if (get_option(&str, &par))
  85                         prof_shift = par;
  86                 pr_info("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                 pr_info("kernel profiling enabled (shift: %ld)\n",
  92                         prof_shift);
  93         }
  94         return 1;
  95 }
  96 __setup("profile=", profile_setup);
  97
  98
  99 int __ref profile_init(void)
 100 {
 101         int buffer_bytes;
 102         if (!prof_on)
 103                 return 0;
 104
 105         /* only text is profiled */
 106         prof_len = (_etext - _stext) >> prof_shift;
 107         buffer_bytes = prof_len*sizeof(atomic_t);
 108
 109         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 110                 return -ENOMEM;
 111
 112         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 113
 114         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 115         if (prof_buffer)
 116                 return 0;
 117
 118         prof_buffer = alloc_pages_exact(buffer_bytes,
 119                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 120         if (prof_buffer)
 121                 return 0;
 122
 123         prof_buffer = vzalloc(buffer_bytes);
 124         if (prof_buffer)
 125                 return 0;
 126
 127         free_cpumask_var(prof_cpu_mask);
 128         return -ENOMEM;
 129 }
 130
 131 /* Profile event notifications */
 132
 133 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 134 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 135 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 136
 137 void profile_task_exit(struct task_struct *task)
 138 {
 139         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 140 }
 141
 142 int profile_handoff_task(struct task_struct *task)
 143 {
 144         int ret;
 145         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 146         return (ret == NOTIFY_OK) ? 1 : 0;
 147 }
 148
 149 void profile_munmap(unsigned long addr)
 150 {
 151         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 152 }
 153
 154 int task_handoff_register(struct notifier_block *n)
 155 {
 156         return atomic_notifier_chain_register(&task_free_notifier, n);
 157 }
 158 EXPORT_SYMBOL_GPL(task_handoff_register);
 159
 160 int task_handoff_unregister(struct notifier_block *n)
 161 {
 162         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 163 }
 164 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 165
 166 int profile_event_register(enum profile_type type, struct notifier_block *n)
 167 {
 168         int err = -EINVAL;
 169
 170         switch (type) {
 171         case PROFILE_TASK_EXIT:
 172                 err = blocking_notifier_chain_register(
 173                                 &task_exit_notifier, n);
 174                 break;
 175         case PROFILE_MUNMAP:
 176                 err = blocking_notifier_chain_register(
 177                                 &munmap_notifier, n);
 178                 break;
 179         }
 180
 181         return err;
 182 }
 183 EXPORT_SYMBOL_GPL(profile_event_register);
 184
 185 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 186 {
 187         int err = -EINVAL;
 188
 189         switch (type) {
 190         case PROFILE_TASK_EXIT:
 191                 err = blocking_notifier_chain_unregister(
 192                                 &task_exit_notifier, n);
 193                 break;
 194         case PROFILE_MUNMAP:
 195                 err = blocking_notifier_chain_unregister(
 196                                 &munmap_notifier, n);
 197                 break;
 198         }
 199
 200         return err;
 201 }
 202 EXPORT_SYMBOL_GPL(profile_event_unregister);
 203
 204 #ifdef CONFIG_SMP
 205 /*
 206  * Each cpu has a pair of open-addressed hashtables for pending
 207  * profile hits. read_profile() IPI's all cpus to request them
 208  * to flip buffers and flushes their contents to prof_buffer itself.
 209  * Flip requests are serialized by the profile_flip_mutex. The sole
 210  * use of having a second hashtable is for avoiding cacheline
 211  * contention that would otherwise happen during flushes of pending
 212  * profile hits required for the accuracy of reported profile hits
 213  * and so resurrect the interrupt livelock issue.
 214  *
 215  * The open-addressed hashtables are indexed by profile buffer slot
 216  * and hold the number of pending hits to that profile buffer slot on
 217  * a cpu in an entry. When the hashtable overflows, all pending hits
 218  * are accounted to their corresponding profile buffer slots with
 219  * atomic_add() and the hashtable emptied. As numerous pending hits
 220  * may be accounted to a profile buffer slot in a hashtable entry,
 221  * this amortizes a number of atomic profile buffer increments likely
 222  * to be far larger than the number of entries in the hashtable,
 223  * particularly given that the number of distinct profile buffer
 224  * positions to which hits are accounted during short intervals (e.g.
 225  * several seconds) is usually very small. Exclusion from buffer
 226  * flipping is provided by interrupt disablement (note that for
 227  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 228  * process context).
 229  * The hash function is meant to be lightweight as opposed to strong,
 230  * and was vaguely inspired by ppc64 firmware-supported inverted
 231  * pagetable hash functions, but uses a full hashtable full of finite
 232  * collision chains, not just pairs of them.
 233  *
 234  * -- nyc
 235  */
 236 static void __profile_flip_buffers(void *unused)
 237 {
 238         int cpu = smp_processor_id();
 239
 240         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 241 }
 242
 243 static void profile_flip_buffers(void)
 244 {
 245         int i, j, cpu;
 246
 247         mutex_lock(&profile_flip_mutex);
 248         j = per_cpu(cpu_profile_flip, get_cpu());
 249         put_cpu();
 250         on_each_cpu(__profile_flip_buffers, NULL, 1);
 251         for_each_online_cpu(cpu) {
 252                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 253                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 254                         if (!hits[i].hits) {
 255                                 if (hits[i].pc)
 256                                         hits[i].pc = 0;
 257                                 continue;
 258                         }
 259                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 260                         hits[i].hits = hits[i].pc = 0;
 261                 }
 262         }
 263         mutex_unlock(&profile_flip_mutex);
 264 }
 265
 266 static void profile_discard_flip_buffers(void)
 267 {
 268         int i, cpu;
 269
 270         mutex_lock(&profile_flip_mutex);
 271         i = per_cpu(cpu_profile_flip, get_cpu());
 272         put_cpu();
 273         on_each_cpu(__profile_flip_buffers, NULL, 1);
 274         for_each_online_cpu(cpu) {
 275                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 276                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 277         }
 278         mutex_unlock(&profile_flip_mutex);
 279 }
 280
 281 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 282 {
 283         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 284         int i, j, cpu;
 285         struct profile_hit *hits;
 286
 287         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 288         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 289         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 290         cpu = get_cpu();
 291         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 292         if (!hits) {
 293                 put_cpu();
 294                 return;
 295         }
 296         /*
 297          * We buffer the global profiler buffer into a per-CPU
 298          * queue and thus reduce the number of global (and possibly
 299          * NUMA-alien) accesses. The write-queue is self-coalescing:
 300          */
 301         local_irq_save(flags);
 302         do {
 303                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 304                         if (hits[i + j].pc == pc) {
 305                                 hits[i + j].hits += nr_hits;
 306                                 goto out;
 307                         } else if (!hits[i + j].hits) {
 308                                 hits[i + j].pc = pc;
 309                                 hits[i + j].hits = nr_hits;
 310                                 goto out;
 311                         }
 312                 }
 313                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 314         } while (i != primary);
 315
 316         /*
 317          * Add the current hit(s) and flush the write-queue out
 318          * to the global buffer:
 319          */
 320         atomic_add(nr_hits, &prof_buffer[pc]);
 321         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 322                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 323                 hits[i].pc = hits[i].hits = 0;
 324         }
 325 out:
 326         local_irq_restore(flags);
 327         put_cpu();
 328 }
 329
 330 static int profile_cpu_callback(struct notifier_block *info,
 331                                         unsigned long action, void *__cpu)
 332 {
 333         int node, cpu = (unsigned long)__cpu;
 334         struct page *page;
 335
 336         switch (action) {
 337         case CPU_UP_PREPARE:
 338         case CPU_UP_PREPARE_FROZEN:
 339                 node = cpu_to_mem(cpu);
 340                 per_cpu(cpu_profile_flip, cpu) = 0;
 341                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 342                         page = __alloc_pages_node(node,
 343                                         GFP_KERNEL | __GFP_ZERO,
 344                                         0);
 345                         if (!page)
 346                                 return notifier_from_errno(-ENOMEM);
 347                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 348                 }
 349                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 350                         page = __alloc_pages_node(node,
 351                                         GFP_KERNEL | __GFP_ZERO,
 352                                         0);
 353                         if (!page)
 354                                 goto out_free;
 355                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 356                 }
 357                 break;
 358 out_free:
 359                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 360                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 361                 __free_page(page);
 362                 return notifier_from_errno(-ENOMEM);
 363         case CPU_ONLINE:
 364         case CPU_ONLINE_FROZEN:
 365                 if (prof_cpu_mask != NULL)
 366                         cpumask_set_cpu(cpu, prof_cpu_mask);
 367                 break;
 368         case CPU_UP_CANCELED:
 369         case CPU_UP_CANCELED_FROZEN:
 370         case CPU_DEAD:
 371         case CPU_DEAD_FROZEN:
 372                 if (prof_cpu_mask != NULL)
 373                         cpumask_clear_cpu(cpu, prof_cpu_mask);
 374                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 375                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 376                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 377                         __free_page(page);
 378                 }
 379                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 380                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 381                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 382                         __free_page(page);
 383                 }
 384                 break;
 385         }
 386         return NOTIFY_OK;
 387 }
 388 #else /* !CONFIG_SMP */
 389 #define profile_flip_buffers()          do { } while (0)
 390 #define profile_discard_flip_buffers()  do { } while (0)
 391 #define profile_cpu_callback            NULL
 392
 393 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 394 {
 395         unsigned long pc;
 396         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 397         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 398 }
 399 #endif /* !CONFIG_SMP */
 400
 401 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 402 {
 403         if (prof_on != type || !prof_buffer)
 404                 return;
 405         do_profile_hits(type, __pc, nr_hits);
 406 }
 407 EXPORT_SYMBOL_GPL(profile_hits);
 408
 409 void profile_tick(int type)
 410 {
 411         struct pt_regs *regs = get_irq_regs();
 412
 413         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 414             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 415                 profile_hit(type, (void *)profile_pc(regs));
 416 }
 417
 418 #ifdef CONFIG_PROC_FS
 419 #include <linux/proc_fs.h>
 420 #include <linux/seq_file.h>
 421 #include <asm/uaccess.h>
 422
 423 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 424 {
 425         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 426         return 0;
 427 }
 428
 429 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 430 {
 431         return single_open(file, prof_cpu_mask_proc_show, NULL);
 432 }
 433
 434 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 435         const char __user *buffer, size_t count, loff_t *pos)
 436 {
 437         cpumask_var_t new_value;
 438         int err;
 439
 440         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 441                 return -ENOMEM;
 442
 443         err = cpumask_parse_user(buffer, count, new_value);
 444         if (!err) {
 445                 cpumask_copy(prof_cpu_mask, new_value);
 446                 err = count;
 447         }
 448         free_cpumask_var(new_value);
 449         return err;
 450 }
 451
 452 static const struct file_operations prof_cpu_mask_proc_fops = {
 453         .open           = prof_cpu_mask_proc_open,
 454         .read           = seq_read,
 455         .llseek         = seq_lseek,
 456         .release        = single_release,
 457         .write          = prof_cpu_mask_proc_write,
 458 };
 459
 460 void create_prof_cpu_mask(void)
 461 {
 462         /* create /proc/irq/prof_cpu_mask */
 463         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 464 }
 465
 466 /*
 467  * This function accesses profiling information. The returned data is
 468  * binary: the sampling step and the actual contents of the profile
 469  * buffer. Use of the program readprofile is recommended in order to
 470  * get meaningful info out of these data.
 471  */
 472 static ssize_t
 473 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 474 {
 475         unsigned long p = *ppos;
 476         ssize_t read;
 477         char *pnt;
 478         unsigned int sample_step = 1 << prof_shift;
 479
 480         profile_flip_buffers();
 481         if (p >= (prof_len+1)*sizeof(unsigned int))
 482                 return 0;
 483         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 484                 count = (prof_len+1)*sizeof(unsigned int) - p;
 485         read = 0;
 486
 487         while (p < sizeof(unsigned int) && count > 0) {
 488                 if (put_user(*((char *)(&sample_step)+p), buf))
 489                         return -EFAULT;
 490                 buf++; p++; count--; read++;
 491         }
 492         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 493         if (copy_to_user(buf, (void *)pnt, count))
 494                 return -EFAULT;
 495         read += count;
 496         *ppos += read;
 497         return read;
 498 }
 499
 500 /*
 501  * Writing to /proc/profile resets the counters
 502  *
 503  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 504  * interrupt frequency, on architectures that support this.
 505  */
 506 static ssize_t write_profile(struct file *file, const char __user *buf,
 507                              size_t count, loff_t *ppos)
 508 {
 509 #ifdef CONFIG_SMP
 510         extern int setup_profiling_timer(unsigned int multiplier);
 511
 512         if (count == sizeof(int)) {
 513                 unsigned int multiplier;
 514
 515                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 516                         return -EFAULT;
 517
 518                 if (setup_profiling_timer(multiplier))
 519                         return -EINVAL;
 520         }
 521 #endif
 522         profile_discard_flip_buffers();
 523         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 524         return count;
 525 }
 526
 527 static const struct file_operations proc_profile_operations = {
 528         .read           = read_profile,
 529         .write          = write_profile,
 530         .llseek         = default_llseek,
 531 };
 532
 533 #ifdef CONFIG_SMP
 534 static void profile_nop(void *unused)
 535 {
 536 }
 537
 538 static int create_hash_tables(void)
 539 {
 540         int cpu;
 541
 542         for_each_online_cpu(cpu) {
 543                 int node = cpu_to_mem(cpu);
 544                 struct page *page;
 545
 546                 page = __alloc_pages_node(node,
 547                                 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 548                                 0);
 549                 if (!page)
 550                         goto out_cleanup;
 551                 per_cpu(cpu_profile_hits, cpu)[1]
 552                                 = (struct profile_hit *)page_address(page);
 553                 page = __alloc_pages_node(node,
 554                                 GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
 555                                 0);
 556                 if (!page)
 557                         goto out_cleanup;
 558                 per_cpu(cpu_profile_hits, cpu)[0]
 559                                 = (struct profile_hit *)page_address(page);
 560         }
 561         return 0;
 562 out_cleanup:
 563         prof_on = 0;
 564         smp_mb();
 565         on_each_cpu(profile_nop, NULL, 1);
 566         for_each_online_cpu(cpu) {
 567                 struct page *page;
 568
 569                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 570                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 571                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 572                         __free_page(page);
 573                 }
 574                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 575                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 576                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 577                         __free_page(page);
 578                 }
 579         }
 580         return -1;
 581 }
 582 #else
 583 #define create_hash_tables()                    ({ 0; })
 584 #endif
 585
 586 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 587 {
 588         struct proc_dir_entry *entry;
 589         int err = 0;
 590
 591         if (!prof_on)
 592                 return 0;
 593
 594         cpu_notifier_register_begin();
 595
 596         if (create_hash_tables()) {
 597                 err = -ENOMEM;
 598                 goto out;
 599         }
 600
 601         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 602                             NULL, &proc_profile_operations);
 603         if (!entry)
 604                 goto out;
 605         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 606         __hotcpu_notifier(profile_cpu_callback, 0);
 607
 608 out:
 609         cpu_notifier_register_done();
 610         return err;
 611 }
 612 subsys_initcall(create_proc_profile);
 613 #endif /* CONFIG_PROC_FS */