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 <linux/slab.h> 26 #include <linux/vmalloc.h> 27 #include <asm/sections.h> 28 #include <asm/irq_regs.h> 29 #include <asm/ptrace.h> 30 31 struct profile_hit { 32 u32 pc, hits; 33 }; 34 #define PROFILE_GRPSHIFT 3 35 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT) 36 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit)) 37 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ) 38 39 /* Oprofile timer tick hook */ 40 static int (*timer_hook)(struct pt_regs *) __read_mostly; 41 42 static atomic_t *prof_buffer; 43 static unsigned long prof_len, prof_shift; 44 45 int prof_on __read_mostly; 46 EXPORT_SYMBOL_GPL(prof_on); 47 48 static cpumask_var_t prof_cpu_mask; 49 #ifdef CONFIG_SMP 50 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits); 51 static DEFINE_PER_CPU(int, cpu_profile_flip); 52 static DEFINE_MUTEX(profile_flip_mutex); 53 #endif /* CONFIG_SMP */ 54 55 int profile_setup(char *str) 56 { 57 static char schedstr[] = "schedule"; 58 static char sleepstr[] = "sleep"; 59 static char kvmstr[] = "kvm"; 60 int par; 61 62 if (!strncmp(str, sleepstr, strlen(sleepstr))) { 63 #ifdef CONFIG_SCHEDSTATS 64 prof_on = SLEEP_PROFILING; 65 if (str[strlen(sleepstr)] == ',') 66 str += strlen(sleepstr) + 1; 67 if (get_option(&str, &par)) 68 prof_shift = par; 69 printk(KERN_INFO 70 "kernel sleep profiling enabled (shift: %ld)\n", 71 prof_shift); 72 #else 73 printk(KERN_WARNING 74 "kernel sleep profiling requires CONFIG_SCHEDSTATS\n"); 75 #endif /* CONFIG_SCHEDSTATS */ 76 } else if (!strncmp(str, schedstr, strlen(schedstr))) { 77 prof_on = SCHED_PROFILING; 78 if (str[strlen(schedstr)] == ',') 79 str += strlen(schedstr) + 1; 80 if (get_option(&str, &par)) 81 prof_shift = par; 82 printk(KERN_INFO 83 "kernel schedule profiling enabled (shift: %ld)\n", 84 prof_shift); 85 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) { 86 prof_on = KVM_PROFILING; 87 if (str[strlen(kvmstr)] == ',') 88 str += strlen(kvmstr) + 1; 89 if (get_option(&str, &par)) 90 prof_shift = par; 91 printk(KERN_INFO 92 "kernel KVM profiling enabled (shift: %ld)\n", 93 prof_shift); 94 } else if (get_option(&str, &par)) { 95 prof_shift = par; 96 prof_on = CPU_PROFILING; 97 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n", 98 prof_shift); 99 } 100 return 1; 101 } 102 __setup("profile=", profile_setup); 103 104 105 int __ref profile_init(void) 106 { 107 int buffer_bytes; 108 if (!prof_on) 109 return 0; 110 111 /* only text is profiled */ 112 prof_len = (_etext - _stext) >> prof_shift; 113 buffer_bytes = prof_len*sizeof(atomic_t); 114 if (!slab_is_available()) { 115 prof_buffer = alloc_bootmem(buffer_bytes); 116 alloc_bootmem_cpumask_var(&prof_cpu_mask); 117 return 0; 118 } 119 120 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL)) 121 return -ENOMEM; 122 123 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL); 124 if (prof_buffer) 125 return 0; 126 127 prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO); 128 if (prof_buffer) 129 return 0; 130 131 prof_buffer = vmalloc(buffer_bytes); 132 if (prof_buffer) 133 return 0; 134 135 free_cpumask_var(prof_cpu_mask); 136 return -ENOMEM; 137 } 138 139 /* Profile event notifications */ 140 141 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier); 142 static ATOMIC_NOTIFIER_HEAD(task_free_notifier); 143 static BLOCKING_NOTIFIER_HEAD(munmap_notifier); 144 145 void profile_task_exit(struct task_struct *task) 146 { 147 blocking_notifier_call_chain(&task_exit_notifier, 0, task); 148 } 149 150 int profile_handoff_task(struct task_struct *task) 151 { 152 int ret; 153 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task); 154 return (ret == NOTIFY_OK) ? 1 : 0; 155 } 156 157 void profile_munmap(unsigned long addr) 158 { 159 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr); 160 } 161 162 int task_handoff_register(struct notifier_block *n) 163 { 164 return atomic_notifier_chain_register(&task_free_notifier, n); 165 } 166 EXPORT_SYMBOL_GPL(task_handoff_register); 167 168 int task_handoff_unregister(struct notifier_block *n) 169 { 170 return atomic_notifier_chain_unregister(&task_free_notifier, n); 171 } 172 EXPORT_SYMBOL_GPL(task_handoff_unregister); 173 174 int profile_event_register(enum profile_type type, struct notifier_block *n) 175 { 176 int err = -EINVAL; 177 178 switch (type) { 179 case PROFILE_TASK_EXIT: 180 err = blocking_notifier_chain_register( 181 &task_exit_notifier, n); 182 break; 183 case PROFILE_MUNMAP: 184 err = blocking_notifier_chain_register( 185 &munmap_notifier, n); 186 break; 187 } 188 189 return err; 190 } 191 EXPORT_SYMBOL_GPL(profile_event_register); 192 193 int profile_event_unregister(enum profile_type type, struct notifier_block *n) 194 { 195 int err = -EINVAL; 196 197 switch (type) { 198 case PROFILE_TASK_EXIT: 199 err = blocking_notifier_chain_unregister( 200 &task_exit_notifier, n); 201 break; 202 case PROFILE_MUNMAP: 203 err = blocking_notifier_chain_unregister( 204 &munmap_notifier, n); 205 break; 206 } 207 208 return err; 209 } 210 EXPORT_SYMBOL_GPL(profile_event_unregister); 211 212 int register_timer_hook(int (*hook)(struct pt_regs *)) 213 { 214 if (timer_hook) 215 return -EBUSY; 216 timer_hook = hook; 217 return 0; 218 } 219 EXPORT_SYMBOL_GPL(register_timer_hook); 220 221 void unregister_timer_hook(int (*hook)(struct pt_regs *)) 222 { 223 WARN_ON(hook != timer_hook); 224 timer_hook = NULL; 225 /* make sure all CPUs see the NULL hook */ 226 synchronize_sched(); /* Allow ongoing interrupts to complete. */ 227 } 228 EXPORT_SYMBOL_GPL(unregister_timer_hook); 229 230 231 #ifdef CONFIG_SMP 232 /* 233 * Each cpu has a pair of open-addressed hashtables for pending 234 * profile hits. read_profile() IPI's all cpus to request them 235 * to flip buffers and flushes their contents to prof_buffer itself. 236 * Flip requests are serialized by the profile_flip_mutex. The sole 237 * use of having a second hashtable is for avoiding cacheline 238 * contention that would otherwise happen during flushes of pending 239 * profile hits required for the accuracy of reported profile hits 240 * and so resurrect the interrupt livelock issue. 241 * 242 * The open-addressed hashtables are indexed by profile buffer slot 243 * and hold the number of pending hits to that profile buffer slot on 244 * a cpu in an entry. When the hashtable overflows, all pending hits 245 * are accounted to their corresponding profile buffer slots with 246 * atomic_add() and the hashtable emptied. As numerous pending hits 247 * may be accounted to a profile buffer slot in a hashtable entry, 248 * this amortizes a number of atomic profile buffer increments likely 249 * to be far larger than the number of entries in the hashtable, 250 * particularly given that the number of distinct profile buffer 251 * positions to which hits are accounted during short intervals (e.g. 252 * several seconds) is usually very small. Exclusion from buffer 253 * flipping is provided by interrupt disablement (note that for 254 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from 255 * process context). 256 * The hash function is meant to be lightweight as opposed to strong, 257 * and was vaguely inspired by ppc64 firmware-supported inverted 258 * pagetable hash functions, but uses a full hashtable full of finite 259 * collision chains, not just pairs of them. 260 * 261 * -- wli 262 */ 263 static void __profile_flip_buffers(void *unused) 264 { 265 int cpu = smp_processor_id(); 266 267 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 268 } 269 270 static void profile_flip_buffers(void) 271 { 272 int i, j, cpu; 273 274 mutex_lock(&profile_flip_mutex); 275 j = 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)[j]; 280 for (i = 0; i < NR_PROFILE_HIT; ++i) { 281 if (!hits[i].hits) { 282 if (hits[i].pc) 283 hits[i].pc = 0; 284 continue; 285 } 286 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 287 hits[i].hits = hits[i].pc = 0; 288 } 289 } 290 mutex_unlock(&profile_flip_mutex); 291 } 292 293 static void profile_discard_flip_buffers(void) 294 { 295 int i, cpu; 296 297 mutex_lock(&profile_flip_mutex); 298 i = per_cpu(cpu_profile_flip, get_cpu()); 299 put_cpu(); 300 on_each_cpu(__profile_flip_buffers, NULL, 1); 301 for_each_online_cpu(cpu) { 302 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 303 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 304 } 305 mutex_unlock(&profile_flip_mutex); 306 } 307 308 void profile_hits(int type, void *__pc, unsigned int nr_hits) 309 { 310 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 311 int i, j, cpu; 312 struct profile_hit *hits; 313 314 if (prof_on != type || !prof_buffer) 315 return; 316 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1); 317 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 318 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 319 cpu = get_cpu(); 320 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)]; 321 if (!hits) { 322 put_cpu(); 323 return; 324 } 325 /* 326 * We buffer the global profiler buffer into a per-CPU 327 * queue and thus reduce the number of global (and possibly 328 * NUMA-alien) accesses. The write-queue is self-coalescing: 329 */ 330 local_irq_save(flags); 331 do { 332 for (j = 0; j < PROFILE_GRPSZ; ++j) { 333 if (hits[i + j].pc == pc) { 334 hits[i + j].hits += nr_hits; 335 goto out; 336 } else if (!hits[i + j].hits) { 337 hits[i + j].pc = pc; 338 hits[i + j].hits = nr_hits; 339 goto out; 340 } 341 } 342 i = (i + secondary) & (NR_PROFILE_HIT - 1); 343 } while (i != primary); 344 345 /* 346 * Add the current hit(s) and flush the write-queue out 347 * to the global buffer: 348 */ 349 atomic_add(nr_hits, &prof_buffer[pc]); 350 for (i = 0; i < NR_PROFILE_HIT; ++i) { 351 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 352 hits[i].pc = hits[i].hits = 0; 353 } 354 out: 355 local_irq_restore(flags); 356 put_cpu(); 357 } 358 359 static int __cpuinit profile_cpu_callback(struct notifier_block *info, 360 unsigned long action, void *__cpu) 361 { 362 int node, cpu = (unsigned long)__cpu; 363 struct page *page; 364 365 switch (action) { 366 case CPU_UP_PREPARE: 367 case CPU_UP_PREPARE_FROZEN: 368 node = cpu_to_node(cpu); 369 per_cpu(cpu_profile_flip, cpu) = 0; 370 if (!per_cpu(cpu_profile_hits, cpu)[1]) { 371 page = alloc_pages_node(node, 372 GFP_KERNEL | __GFP_ZERO, 373 0); 374 if (!page) 375 return NOTIFY_BAD; 376 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page); 377 } 378 if (!per_cpu(cpu_profile_hits, cpu)[0]) { 379 page = alloc_pages_node(node, 380 GFP_KERNEL | __GFP_ZERO, 381 0); 382 if (!page) 383 goto out_free; 384 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page); 385 } 386 break; 387 out_free: 388 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 389 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 390 __free_page(page); 391 return NOTIFY_BAD; 392 case CPU_ONLINE: 393 case CPU_ONLINE_FROZEN: 394 if (prof_cpu_mask != NULL) 395 cpumask_set_cpu(cpu, prof_cpu_mask); 396 break; 397 case CPU_UP_CANCELED: 398 case CPU_UP_CANCELED_FROZEN: 399 case CPU_DEAD: 400 case CPU_DEAD_FROZEN: 401 if (prof_cpu_mask != NULL) 402 cpumask_clear_cpu(cpu, prof_cpu_mask); 403 if (per_cpu(cpu_profile_hits, cpu)[0]) { 404 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 405 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 406 __free_page(page); 407 } 408 if (per_cpu(cpu_profile_hits, cpu)[1]) { 409 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 410 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 411 __free_page(page); 412 } 413 break; 414 } 415 return NOTIFY_OK; 416 } 417 #else /* !CONFIG_SMP */ 418 #define profile_flip_buffers() do { } while (0) 419 #define profile_discard_flip_buffers() do { } while (0) 420 #define profile_cpu_callback NULL 421 422 void profile_hits(int type, void *__pc, unsigned int nr_hits) 423 { 424 unsigned long pc; 425 426 if (prof_on != type || !prof_buffer) 427 return; 428 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 429 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); 430 } 431 #endif /* !CONFIG_SMP */ 432 EXPORT_SYMBOL_GPL(profile_hits); 433 434 void profile_tick(int type) 435 { 436 struct pt_regs *regs = get_irq_regs(); 437 438 if (type == CPU_PROFILING && timer_hook) 439 timer_hook(regs); 440 if (!user_mode(regs) && prof_cpu_mask != NULL && 441 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask)) 442 profile_hit(type, (void *)profile_pc(regs)); 443 } 444 445 #ifdef CONFIG_PROC_FS 446 #include <linux/proc_fs.h> 447 #include <asm/uaccess.h> 448 449 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off, 450 int count, int *eof, void *data) 451 { 452 int len = cpumask_scnprintf(page, count, data); 453 if (count - len < 2) 454 return -EINVAL; 455 len += sprintf(page + len, "\n"); 456 return len; 457 } 458 459 static int prof_cpu_mask_write_proc(struct file *file, 460 const char __user *buffer, unsigned long count, void *data) 461 { 462 struct cpumask *mask = data; 463 unsigned long full_count = count, err; 464 cpumask_var_t new_value; 465 466 if (!alloc_cpumask_var(&new_value, GFP_KERNEL)) 467 return -ENOMEM; 468 469 err = cpumask_parse_user(buffer, count, new_value); 470 if (!err) { 471 cpumask_copy(mask, new_value); 472 err = full_count; 473 } 474 free_cpumask_var(new_value); 475 return err; 476 } 477 478 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir) 479 { 480 struct proc_dir_entry *entry; 481 482 /* create /proc/irq/prof_cpu_mask */ 483 entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir); 484 if (!entry) 485 return; 486 entry->data = prof_cpu_mask; 487 entry->read_proc = prof_cpu_mask_read_proc; 488 entry->write_proc = prof_cpu_mask_write_proc; 489 } 490 491 /* 492 * This function accesses profiling information. The returned data is 493 * binary: the sampling step and the actual contents of the profile 494 * buffer. Use of the program readprofile is recommended in order to 495 * get meaningful info out of these data. 496 */ 497 static ssize_t 498 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos) 499 { 500 unsigned long p = *ppos; 501 ssize_t read; 502 char *pnt; 503 unsigned int sample_step = 1 << prof_shift; 504 505 profile_flip_buffers(); 506 if (p >= (prof_len+1)*sizeof(unsigned int)) 507 return 0; 508 if (count > (prof_len+1)*sizeof(unsigned int) - p) 509 count = (prof_len+1)*sizeof(unsigned int) - p; 510 read = 0; 511 512 while (p < sizeof(unsigned int) && count > 0) { 513 if (put_user(*((char *)(&sample_step)+p), buf)) 514 return -EFAULT; 515 buf++; p++; count--; read++; 516 } 517 pnt = (char *)prof_buffer + p - sizeof(atomic_t); 518 if (copy_to_user(buf, (void *)pnt, count)) 519 return -EFAULT; 520 read += count; 521 *ppos += read; 522 return read; 523 } 524 525 /* 526 * Writing to /proc/profile resets the counters 527 * 528 * Writing a 'profiling multiplier' value into it also re-sets the profiling 529 * interrupt frequency, on architectures that support this. 530 */ 531 static ssize_t write_profile(struct file *file, const char __user *buf, 532 size_t count, loff_t *ppos) 533 { 534 #ifdef CONFIG_SMP 535 extern int setup_profiling_timer(unsigned int multiplier); 536 537 if (count == sizeof(int)) { 538 unsigned int multiplier; 539 540 if (copy_from_user(&multiplier, buf, sizeof(int))) 541 return -EFAULT; 542 543 if (setup_profiling_timer(multiplier)) 544 return -EINVAL; 545 } 546 #endif 547 profile_discard_flip_buffers(); 548 memset(prof_buffer, 0, prof_len * sizeof(atomic_t)); 549 return count; 550 } 551 552 static const struct file_operations proc_profile_operations = { 553 .read = read_profile, 554 .write = write_profile, 555 }; 556 557 #ifdef CONFIG_SMP 558 static void profile_nop(void *unused) 559 { 560 } 561 562 static int create_hash_tables(void) 563 { 564 int cpu; 565 566 for_each_online_cpu(cpu) { 567 int node = cpu_to_node(cpu); 568 struct page *page; 569 570 page = alloc_pages_node(node, 571 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 572 0); 573 if (!page) 574 goto out_cleanup; 575 per_cpu(cpu_profile_hits, cpu)[1] 576 = (struct profile_hit *)page_address(page); 577 page = alloc_pages_node(node, 578 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 579 0); 580 if (!page) 581 goto out_cleanup; 582 per_cpu(cpu_profile_hits, cpu)[0] 583 = (struct profile_hit *)page_address(page); 584 } 585 return 0; 586 out_cleanup: 587 prof_on = 0; 588 smp_mb(); 589 on_each_cpu(profile_nop, NULL, 1); 590 for_each_online_cpu(cpu) { 591 struct page *page; 592 593 if (per_cpu(cpu_profile_hits, cpu)[0]) { 594 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 595 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 596 __free_page(page); 597 } 598 if (per_cpu(cpu_profile_hits, cpu)[1]) { 599 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 600 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 601 __free_page(page); 602 } 603 } 604 return -1; 605 } 606 #else 607 #define create_hash_tables() ({ 0; }) 608 #endif 609 610 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */ 611 { 612 struct proc_dir_entry *entry; 613 614 if (!prof_on) 615 return 0; 616 if (create_hash_tables()) 617 return -ENOMEM; 618 entry = proc_create("profile", S_IWUSR | S_IRUGO, 619 NULL, &proc_profile_operations); 620 if (!entry) 621 return 0; 622 entry->size = (1+prof_len) * sizeof(atomic_t); 623 hotcpu_notifier(profile_cpu_callback, 0); 624 return 0; 625 } 626 module_init(create_proc_profile); 627 #endif /* CONFIG_PROC_FS */ 628