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 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
  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                 force_schedstat_enabled();
  63                 prof_on = SLEEP_PROFILING;
  64                 if (str[strlen(sleepstr)] == ',')
  65                         str += strlen(sleepstr) + 1;
  66                 if (get_option(&str, &par))
  67                         prof_shift = par;
  68                 pr_info("kernel sleep profiling enabled (shift: %ld)\n",
  69                         prof_shift);
  70 #else
  71                 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  72 #endif /* CONFIG_SCHEDSTATS */
  73         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  74                 prof_on = SCHED_PROFILING;
  75                 if (str[strlen(schedstr)] == ',')
  76                         str += strlen(schedstr) + 1;
  77                 if (get_option(&str, &par))
  78                         prof_shift = par;
  79                 pr_info("kernel schedule profiling enabled (shift: %ld)\n",
  80                         prof_shift);
  81         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  82                 prof_on = KVM_PROFILING;
  83                 if (str[strlen(kvmstr)] == ',')
  84                         str += strlen(kvmstr) + 1;
  85                 if (get_option(&str, &par))
  86                         prof_shift = par;
  87                 pr_info("kernel KVM profiling enabled (shift: %ld)\n",
  88                         prof_shift);
  89         } else if (get_option(&str, &par)) {
  90                 prof_shift = par;
  91                 prof_on = CPU_PROFILING;
  92                 pr_info("kernel profiling enabled (shift: %ld)\n",
  93                         prof_shift);
  94         }
  95         return 1;
  96 }
  97 __setup("profile=", profile_setup);
  98
  99
 100 int __ref profile_init(void)
 101 {
 102         int buffer_bytes;
 103         if (!prof_on)
 104                 return 0;
 105
 106         /* only text is profiled */
 107         prof_len = (_etext - _stext) >> prof_shift;
 108         buffer_bytes = prof_len*sizeof(atomic_t);
 109
 110         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 111                 return -ENOMEM;
 112
 113         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 114
 115         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 116         if (prof_buffer)
 117                 return 0;
 118
 119         prof_buffer = alloc_pages_exact(buffer_bytes,
 120                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 121         if (prof_buffer)
 122                 return 0;
 123
 124         prof_buffer = vzalloc(buffer_bytes);
 125         if (prof_buffer)
 126                 return 0;
 127
 128         free_cpumask_var(prof_cpu_mask);
 129         return -ENOMEM;
 130 }
 131
 132 /* Profile event notifications */
 133
 134 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 135 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 136 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 137
 138 void profile_task_exit(struct task_struct *task)
 139 {
 140         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 141 }
 142
 143 int profile_handoff_task(struct task_struct *task)
 144 {
 145         int ret;
 146         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 147         return (ret == NOTIFY_OK) ? 1 : 0;
 148 }
 149
 150 void profile_munmap(unsigned long addr)
 151 {
 152         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 153 }
 154
 155 int task_handoff_register(struct notifier_block *n)
 156 {
 157         return atomic_notifier_chain_register(&task_free_notifier, n);
 158 }
 159 EXPORT_SYMBOL_GPL(task_handoff_register);
 160
 161 int task_handoff_unregister(struct notifier_block *n)
 162 {
 163         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 164 }
 165 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 166
 167 int profile_event_register(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_register(
 174                                 &task_exit_notifier, n);
 175                 break;
 176         case PROFILE_MUNMAP:
 177                 err = blocking_notifier_chain_register(
 178                                 &munmap_notifier, n);
 179                 break;
 180         }
 181
 182         return err;
 183 }
 184 EXPORT_SYMBOL_GPL(profile_event_register);
 185
 186 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 187 {
 188         int err = -EINVAL;
 189
 190         switch (type) {
 191         case PROFILE_TASK_EXIT:
 192                 err = blocking_notifier_chain_unregister(
 193                                 &task_exit_notifier, n);
 194                 break;
 195         case PROFILE_MUNMAP:
 196                 err = blocking_notifier_chain_unregister(
 197                                 &munmap_notifier, n);
 198                 break;
 199         }
 200
 201         return err;
 202 }
 203 EXPORT_SYMBOL_GPL(profile_event_unregister);
 204
 205 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 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  * -- nyc
 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 static void do_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         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 289         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 290         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 291         cpu = get_cpu();
 292         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 293         if (!hits) {
 294                 put_cpu();
 295                 return;
 296         }
 297         /*
 298          * We buffer the global profiler buffer into a per-CPU
 299          * queue and thus reduce the number of global (and possibly
 300          * NUMA-alien) accesses. The write-queue is self-coalescing:
 301          */
 302         local_irq_save(flags);
 303         do {
 304                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 305                         if (hits[i + j].pc == pc) {
 306                                 hits[i + j].hits += nr_hits;
 307                                 goto out;
 308                         } else if (!hits[i + j].hits) {
 309                                 hits[i + j].pc = pc;
 310                                 hits[i + j].hits = nr_hits;
 311                                 goto out;
 312                         }
 313                 }
 314                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 315         } while (i != primary);
 316
 317         /*
 318          * Add the current hit(s) and flush the write-queue out
 319          * to the global buffer:
 320          */
 321         atomic_add(nr_hits, &prof_buffer[pc]);
 322         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 323                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 324                 hits[i].pc = hits[i].hits = 0;
 325         }
 326 out:
 327         local_irq_restore(flags);
 328         put_cpu();
 329 }
 330
 331 static int profile_dead_cpu(unsigned int cpu)
 332 {
 333         struct page *page;
 334         int i;
 335
 336         if (prof_cpu_mask != NULL)
 337                 cpumask_clear_cpu(cpu, prof_cpu_mask);
 338
 339         for (i = 0; i < 2; i++) {
 340                 if (per_cpu(cpu_profile_hits, cpu)[i]) {
 341                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
 342                         per_cpu(cpu_profile_hits, cpu)[i] = NULL;
 343                         __free_page(page);
 344                 }
 345         }
 346         return 0;
 347 }
 348
 349 static int profile_prepare_cpu(unsigned int cpu)
 350 {
 351         int i, node = cpu_to_mem(cpu);
 352         struct page *page;
 353
 354         per_cpu(cpu_profile_flip, cpu) = 0;
 355
 356         for (i = 0; i < 2; i++) {
 357                 if (per_cpu(cpu_profile_hits, cpu)[i])
 358                         continue;
 359
 360                 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 361                 if (!page) {
 362                         profile_dead_cpu(cpu);
 363                         return -ENOMEM;
 364                 }
 365                 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
 366
 367         }
 368         return 0;
 369 }
 370
 371 static int profile_online_cpu(unsigned int cpu)
 372 {
 373         if (prof_cpu_mask != NULL)
 374                 cpumask_set_cpu(cpu, prof_cpu_mask);
 375
 376         return 0;
 377 }
 378
 379 #else /* !CONFIG_SMP */
 380 #define profile_flip_buffers()          do { } while (0)
 381 #define profile_discard_flip_buffers()  do { } while (0)
 382
 383 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 384 {
 385         unsigned long pc;
 386         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 387         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 388 }
 389 #endif /* !CONFIG_SMP */
 390
 391 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 392 {
 393         if (prof_on != type || !prof_buffer)
 394                 return;
 395         do_profile_hits(type, __pc, nr_hits);
 396 }
 397 EXPORT_SYMBOL_GPL(profile_hits);
 398
 399 void profile_tick(int type)
 400 {
 401         struct pt_regs *regs = get_irq_regs();
 402
 403         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 404             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 405                 profile_hit(type, (void *)profile_pc(regs));
 406 }
 407
 408 #ifdef CONFIG_PROC_FS
 409 #include <linux/proc_fs.h>
 410 #include <linux/seq_file.h>
 411 #include <linux/uaccess.h>
 412
 413 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 414 {
 415         seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 416         return 0;
 417 }
 418
 419 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 420 {
 421         return single_open(file, prof_cpu_mask_proc_show, NULL);
 422 }
 423
 424 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 425         const char __user *buffer, size_t count, loff_t *pos)
 426 {
 427         cpumask_var_t new_value;
 428         int err;
 429
 430         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 431                 return -ENOMEM;
 432
 433         err = cpumask_parse_user(buffer, count, new_value);
 434         if (!err) {
 435                 cpumask_copy(prof_cpu_mask, new_value);
 436                 err = count;
 437         }
 438         free_cpumask_var(new_value);
 439         return err;
 440 }
 441
 442 static const struct file_operations prof_cpu_mask_proc_fops = {
 443         .open           = prof_cpu_mask_proc_open,
 444         .read           = seq_read,
 445         .llseek         = seq_lseek,
 446         .release        = single_release,
 447         .write          = prof_cpu_mask_proc_write,
 448 };
 449
 450 void create_prof_cpu_mask(void)
 451 {
 452         /* create /proc/irq/prof_cpu_mask */
 453         proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 454 }
 455
 456 /*
 457  * This function accesses profiling information. The returned data is
 458  * binary: the sampling step and the actual contents of the profile
 459  * buffer. Use of the program readprofile is recommended in order to
 460  * get meaningful info out of these data.
 461  */
 462 static ssize_t
 463 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 464 {
 465         unsigned long p = *ppos;
 466         ssize_t read;
 467         char *pnt;
 468         unsigned int sample_step = 1 << prof_shift;
 469
 470         profile_flip_buffers();
 471         if (p >= (prof_len+1)*sizeof(unsigned int))
 472                 return 0;
 473         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 474                 count = (prof_len+1)*sizeof(unsigned int) - p;
 475         read = 0;
 476
 477         while (p < sizeof(unsigned int) && count > 0) {
 478                 if (put_user(*((char *)(&sample_step)+p), buf))
 479                         return -EFAULT;
 480                 buf++; p++; count--; read++;
 481         }
 482         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 483         if (copy_to_user(buf, (void *)pnt, count))
 484                 return -EFAULT;
 485         read += count;
 486         *ppos += read;
 487         return read;
 488 }
 489
 490 /*
 491  * Writing to /proc/profile resets the counters
 492  *
 493  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 494  * interrupt frequency, on architectures that support this.
 495  */
 496 static ssize_t write_profile(struct file *file, const char __user *buf,
 497                              size_t count, loff_t *ppos)
 498 {
 499 #ifdef CONFIG_SMP
 500         extern int setup_profiling_timer(unsigned int multiplier);
 501
 502         if (count == sizeof(int)) {
 503                 unsigned int multiplier;
 504
 505                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 506                         return -EFAULT;
 507
 508                 if (setup_profiling_timer(multiplier))
 509                         return -EINVAL;
 510         }
 511 #endif
 512         profile_discard_flip_buffers();
 513         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 514         return count;
 515 }
 516
 517 static const struct file_operations proc_profile_operations = {
 518         .read           = read_profile,
 519         .write          = write_profile,
 520         .llseek         = default_llseek,
 521 };
 522
 523 int __ref create_proc_profile(void)
 524 {
 525         struct proc_dir_entry *entry;
 526 #ifdef CONFIG_SMP
 527         enum cpuhp_state online_state;
 528 #endif
 529
 530         int err = 0;
 531
 532         if (!prof_on)
 533                 return 0;
 534 #ifdef CONFIG_SMP
 535         err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
 536                                 profile_prepare_cpu, profile_dead_cpu);
 537         if (err)
 538                 return err;
 539
 540         err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
 541                                 profile_online_cpu, NULL);
 542         if (err < 0)
 543                 goto err_state_prep;
 544         online_state = err;
 545         err = 0;
 546 #endif
 547         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 548                             NULL, &proc_profile_operations);
 549         if (!entry)
 550                 goto err_state_onl;
 551         proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
 552
 553         return err;
 554 err_state_onl:
 555 #ifdef CONFIG_SMP
 556         cpuhp_remove_state(online_state);
 557 err_state_prep:
 558         cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
 559 #endif
 560         return err;
 561 }
 562 subsys_initcall(create_proc_profile);
 563 #endif /* CONFIG_PROC_FS */