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;
  42 static unsigned short int prof_shift;
  43
  44 int prof_on __read_mostly;
  45 EXPORT_SYMBOL_GPL(prof_on);
  46
  47 static cpumask_var_t prof_cpu_mask;
  48 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
  49 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  50 static DEFINE_PER_CPU(int, cpu_profile_flip);
  51 static DEFINE_MUTEX(profile_flip_mutex);
  52 #endif /* CONFIG_SMP */
  53
  54 int profile_setup(char *str)
  55 {
  56         static const char schedstr[] = "schedule";
  57         static const char sleepstr[] = "sleep";
  58         static const char kvmstr[] = "kvm";
  59         int par;
  60
  61         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  62 #ifdef CONFIG_SCHEDSTATS
  63                 force_schedstat_enabled();
  64                 prof_on = SLEEP_PROFILING;
  65                 if (str[strlen(sleepstr)] == ',')
  66                         str += strlen(sleepstr) + 1;
  67                 if (get_option(&str, &par))
  68                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  69                 pr_info("kernel sleep profiling enabled (shift: %u)\n",
  70                         prof_shift);
  71 #else
  72                 pr_warn("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 = clamp(par, 0, BITS_PER_LONG - 1);
  80                 pr_info("kernel schedule profiling enabled (shift: %u)\n",
  81                         prof_shift);
  82         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  83                 prof_on = KVM_PROFILING;
  84                 if (str[strlen(kvmstr)] == ',')
  85                         str += strlen(kvmstr) + 1;
  86                 if (get_option(&str, &par))
  87                         prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  88                 pr_info("kernel KVM profiling enabled (shift: %u)\n",
  89                         prof_shift);
  90         } else if (get_option(&str, &par)) {
  91                 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
  92                 prof_on = CPU_PROFILING;
  93                 pr_info("kernel profiling enabled (shift: %u)\n",
  94                         prof_shift);
  95         }
  96         return 1;
  97 }
  98 __setup("profile=", profile_setup);
  99
 100
 101 int __ref profile_init(void)
 102 {
 103         int buffer_bytes;
 104         if (!prof_on)
 105                 return 0;
 106
 107         /* only text is profiled */
 108         prof_len = (_etext - _stext) >> prof_shift;
 109         buffer_bytes = prof_len*sizeof(atomic_t);
 110
 111         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 112                 return -ENOMEM;
 113
 114         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 115
 116         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 117         if (prof_buffer)
 118                 return 0;
 119
 120         prof_buffer = alloc_pages_exact(buffer_bytes,
 121                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 122         if (prof_buffer)
 123                 return 0;
 124
 125         prof_buffer = vzalloc(buffer_bytes);
 126         if (prof_buffer)
 127                 return 0;
 128
 129         free_cpumask_var(prof_cpu_mask);
 130         return -ENOMEM;
 131 }
 132
 133 /* Profile event notifications */
 134
 135 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 136 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 137 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 138
 139 void profile_task_exit(struct task_struct *task)
 140 {
 141         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 142 }
 143
 144 int profile_handoff_task(struct task_struct *task)
 145 {
 146         int ret;
 147         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 148         return (ret == NOTIFY_OK) ? 1 : 0;
 149 }
 150
 151 void profile_munmap(unsigned long addr)
 152 {
 153         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 154 }
 155
 156 int task_handoff_register(struct notifier_block *n)
 157 {
 158         return atomic_notifier_chain_register(&task_free_notifier, n);
 159 }
 160 EXPORT_SYMBOL_GPL(task_handoff_register);
 161
 162 int task_handoff_unregister(struct notifier_block *n)
 163 {
 164         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 165 }
 166 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 167
 168 int profile_event_register(enum profile_type type, struct notifier_block *n)
 169 {
 170         int err = -EINVAL;
 171
 172         switch (type) {
 173         case PROFILE_TASK_EXIT:
 174                 err = blocking_notifier_chain_register(
 175                                 &task_exit_notifier, n);
 176                 break;
 177         case PROFILE_MUNMAP:
 178                 err = blocking_notifier_chain_register(
 179                                 &munmap_notifier, n);
 180                 break;
 181         }
 182
 183         return err;
 184 }
 185 EXPORT_SYMBOL_GPL(profile_event_register);
 186
 187 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 188 {
 189         int err = -EINVAL;
 190
 191         switch (type) {
 192         case PROFILE_TASK_EXIT:
 193                 err = blocking_notifier_chain_unregister(
 194                                 &task_exit_notifier, n);
 195                 break;
 196         case PROFILE_MUNMAP:
 197                 err = blocking_notifier_chain_unregister(
 198                                 &munmap_notifier, n);
 199                 break;
 200         }
 201
 202         return err;
 203 }
 204 EXPORT_SYMBOL_GPL(profile_event_unregister);
 205
 206 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 207 /*
 208  * Each cpu has a pair of open-addressed hashtables for pending
 209  * profile hits. read_profile() IPI's all cpus to request them
 210  * to flip buffers and flushes their contents to prof_buffer itself.
 211  * Flip requests are serialized by the profile_flip_mutex. The sole
 212  * use of having a second hashtable is for avoiding cacheline
 213  * contention that would otherwise happen during flushes of pending
 214  * profile hits required for the accuracy of reported profile hits
 215  * and so resurrect the interrupt livelock issue.
 216  *
 217  * The open-addressed hashtables are indexed by profile buffer slot
 218  * and hold the number of pending hits to that profile buffer slot on
 219  * a cpu in an entry. When the hashtable overflows, all pending hits
 220  * are accounted to their corresponding profile buffer slots with
 221  * atomic_add() and the hashtable emptied. As numerous pending hits
 222  * may be accounted to a profile buffer slot in a hashtable entry,
 223  * this amortizes a number of atomic profile buffer increments likely
 224  * to be far larger than the number of entries in the hashtable,
 225  * particularly given that the number of distinct profile buffer
 226  * positions to which hits are accounted during short intervals (e.g.
 227  * several seconds) is usually very small. Exclusion from buffer
 228  * flipping is provided by interrupt disablement (note that for
 229  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 230  * process context).
 231  * The hash function is meant to be lightweight as opposed to strong,
 232  * and was vaguely inspired by ppc64 firmware-supported inverted
 233  * pagetable hash functions, but uses a full hashtable full of finite
 234  * collision chains, not just pairs of them.
 235  *
 236  * -- nyc
 237  */
 238 static void __profile_flip_buffers(void *unused)
 239 {
 240         int cpu = smp_processor_id();
 241
 242         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 243 }
 244
 245 static void profile_flip_buffers(void)
 246 {
 247         int i, j, cpu;
 248
 249         mutex_lock(&profile_flip_mutex);
 250         j = per_cpu(cpu_profile_flip, get_cpu());
 251         put_cpu();
 252         on_each_cpu(__profile_flip_buffers, NULL, 1);
 253         for_each_online_cpu(cpu) {
 254                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 255                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 256                         if (!hits[i].hits) {
 257                                 if (hits[i].pc)
 258                                         hits[i].pc = 0;
 259                                 continue;
 260                         }
 261                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 262                         hits[i].hits = hits[i].pc = 0;
 263                 }
 264         }
 265         mutex_unlock(&profile_flip_mutex);
 266 }
 267
 268 static void profile_discard_flip_buffers(void)
 269 {
 270         int i, cpu;
 271
 272         mutex_lock(&profile_flip_mutex);
 273         i = per_cpu(cpu_profile_flip, get_cpu());
 274         put_cpu();
 275         on_each_cpu(__profile_flip_buffers, NULL, 1);
 276         for_each_online_cpu(cpu) {
 277                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 278                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 279         }
 280         mutex_unlock(&profile_flip_mutex);
 281 }
 282
 283 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 284 {
 285         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 286         int i, j, cpu;
 287         struct profile_hit *hits;
 288
 289         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 290         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 291         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 292         cpu = get_cpu();
 293         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 294         if (!hits) {
 295                 put_cpu();
 296                 return;
 297         }
 298         /*
 299          * We buffer the global profiler buffer into a per-CPU
 300          * queue and thus reduce the number of global (and possibly
 301          * NUMA-alien) accesses. The write-queue is self-coalescing:
 302          */
 303         local_irq_save(flags);
 304         do {
 305                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 306                         if (hits[i + j].pc == pc) {
 307                                 hits[i + j].hits += nr_hits;
 308                                 goto out;
 309                         } else if (!hits[i + j].hits) {
 310                                 hits[i + j].pc = pc;
 311                                 hits[i + j].hits = nr_hits;
 312                                 goto out;
 313                         }
 314                 }
 315                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 316         } while (i != primary);
 317
 318         /*
 319          * Add the current hit(s) and flush the write-queue out
 320          * to the global buffer:
 321          */
 322         atomic_add(nr_hits, &prof_buffer[pc]);
 323         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 324                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 325                 hits[i].pc = hits[i].hits = 0;
 326         }
 327 out:
 328         local_irq_restore(flags);
 329         put_cpu();
 330 }
 331
 332 static int profile_dead_cpu(unsigned int cpu)
 333 {
 334         struct page *page;
 335         int i;
 336
 337         if (prof_cpu_mask != NULL)
 338                 cpumask_clear_cpu(cpu, prof_cpu_mask);
 339
 340         for (i = 0; i < 2; i++) {
 341                 if (per_cpu(cpu_profile_hits, cpu)[i]) {
 342                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
 343                         per_cpu(cpu_profile_hits, cpu)[i] = NULL;
 344                         __free_page(page);
 345                 }
 346         }
 347         return 0;
 348 }
 349
 350 static int profile_prepare_cpu(unsigned int cpu)
 351 {
 352         int i, node = cpu_to_mem(cpu);
 353         struct page *page;
 354
 355         per_cpu(cpu_profile_flip, cpu) = 0;
 356
 357         for (i = 0; i < 2; i++) {
 358                 if (per_cpu(cpu_profile_hits, cpu)[i])
 359                         continue;
 360
 361                 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 362                 if (!page) {
 363                         profile_dead_cpu(cpu);
 364                         return -ENOMEM;
 365                 }
 366                 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
 367
 368         }
 369         return 0;
 370 }
 371
 372 static int profile_online_cpu(unsigned int cpu)
 373 {
 374         if (prof_cpu_mask != NULL)
 375                 cpumask_set_cpu(cpu, prof_cpu_mask);
 376
 377         return 0;
 378 }
 379
 380 #else /* !CONFIG_SMP */
 381 #define profile_flip_buffers()          do { } while (0)
 382 #define profile_discard_flip_buffers()  do { } while (0)
 383
 384 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 385 {
 386         unsigned long pc;
 387         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 388         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 389 }
 390 #endif /* !CONFIG_SMP */
 391
 392 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 393 {
 394         if (prof_on != type || !prof_buffer)
 395                 return;
 396         do_profile_hits(type, __pc, nr_hits);
 397 }
 398 EXPORT_SYMBOL_GPL(profile_hits);
 399
 400 void profile_tick(int type)
 401 {
 402         struct pt_regs *regs = get_irq_regs();
 403
 404         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 405             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 406                 profile_hit(type, (void *)profile_pc(regs));
 407 }
 408
 409 #ifdef CONFIG_PROC_FS
 410 #include <linux/proc_fs.h>
 411 #include <linux/seq_file.h>
 412 #include <asm/uaccess.h>
 413
 414 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 415 {
 416         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 417         return 0;
 418 }
 419
 420 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 421 {
 422         return single_open(file, prof_cpu_mask_proc_show, NULL);
 423 }
 424
 425 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 426         const char __user *buffer, size_t count, loff_t *pos)
 427 {
 428         cpumask_var_t new_value;
 429         int err;
 430
 431         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 432                 return -ENOMEM;
 433
 434         err = cpumask_parse_user(buffer, count, new_value);
 435         if (!err) {
 436                 cpumask_copy(prof_cpu_mask, new_value);
 437                 err = count;
 438         }
 439         free_cpumask_var(new_value);
 440         return err;
 441 }
 442
 443 static const struct file_operations prof_cpu_mask_proc_fops = {
 444         .open           = prof_cpu_mask_proc_open,
 445         .read           = seq_read,
 446         .llseek         = seq_lseek,
 447         .release        = single_release,
 448         .write          = prof_cpu_mask_proc_write,
 449 };
 450
 451 void create_prof_cpu_mask(void)
 452 {
 453         /* create /proc/irq/prof_cpu_mask */
 454         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 455 }
 456
 457 /*
 458  * This function accesses profiling information. The returned data is
 459  * binary: the sampling step and the actual contents of the profile
 460  * buffer. Use of the program readprofile is recommended in order to
 461  * get meaningful info out of these data.
 462  */
 463 static ssize_t
 464 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 465 {
 466         unsigned long p = *ppos;
 467         ssize_t read;
 468         char *pnt;
 469         unsigned long sample_step = 1UL << prof_shift;
 470
 471         profile_flip_buffers();
 472         if (p >= (prof_len+1)*sizeof(unsigned int))
 473                 return 0;
 474         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 475                 count = (prof_len+1)*sizeof(unsigned int) - p;
 476         read = 0;
 477
 478         while (p < sizeof(unsigned int) && count > 0) {
 479                 if (put_user(*((char *)(&sample_step)+p), buf))
 480                         return -EFAULT;
 481                 buf++; p++; count--; read++;
 482         }
 483         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 484         if (copy_to_user(buf, (void *)pnt, count))
 485                 return -EFAULT;
 486         read += count;
 487         *ppos += read;
 488         return read;
 489 }
 490
 491 /*
 492  * Writing to /proc/profile resets the counters
 493  *
 494  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 495  * interrupt frequency, on architectures that support this.
 496  */
 497 static ssize_t write_profile(struct file *file, const char __user *buf,
 498                              size_t count, loff_t *ppos)
 499 {
 500 #ifdef CONFIG_SMP
 501         extern int setup_profiling_timer(unsigned int multiplier);
 502
 503         if (count == sizeof(int)) {
 504                 unsigned int multiplier;
 505
 506                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 507                         return -EFAULT;
 508
 509                 if (setup_profiling_timer(multiplier))
 510                         return -EINVAL;
 511         }
 512 #endif
 513         profile_discard_flip_buffers();
 514         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 515         return count;
 516 }
 517
 518 static const struct file_operations proc_profile_operations = {
 519         .read           = read_profile,
 520         .write          = write_profile,
 521         .llseek         = default_llseek,
 522 };
 523
 524 int __ref create_proc_profile(void)
 525 {
 526         struct proc_dir_entry *entry;
 527 #ifdef CONFIG_SMP
 528         enum cpuhp_state online_state;
 529 #endif
 530
 531         int err = 0;
 532
 533         if (!prof_on)
 534                 return 0;
 535 #ifdef CONFIG_SMP
 536         err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
 537                                 profile_prepare_cpu, profile_dead_cpu);
 538         if (err)
 539                 return err;
 540
 541         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
 542                                 profile_online_cpu, NULL);
 543         if (err < 0)
 544                 goto err_state_prep;
 545         online_state = err;
 546         err = 0;
 547 #endif
 548         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 549                             NULL, &proc_profile_operations);
 550         if (!entry)
 551                 goto err_state_onl;
 552         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 553
 554         return err;
 555 err_state_onl:
 556 #ifdef CONFIG_SMP
 557         cpuhp_remove_state(online_state);
 558 err_state_prep:
 559         cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
 560 #endif
 561         return err;
 562 }
 563 subsys_initcall(create_proc_profile);
 564 #endif /* CONFIG_PROC_FS */