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/profile.h> 24 #include <linux/highmem.h> 25 #include <linux/mutex.h> 26 #include <asm/sections.h> 27 #include <asm/semaphore.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_t prof_cpu_mask = CPU_MASK_ALL; 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 static int __init profile_setup(char * str) 56 { 57 static char __initdata schedstr[] = "schedule"; 58 static char __initdata sleepstr[] = "sleep"; 59 static char __initdata 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 void __init profile_init(void) 106 { 107 if (!prof_on) 108 return; 109 110 /* only text is profiled */ 111 prof_len = (_etext - _stext) >> prof_shift; 112 prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t)); 113 } 114 115 /* Profile event notifications */ 116 117 #ifdef CONFIG_PROFILING 118 119 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier); 120 static ATOMIC_NOTIFIER_HEAD(task_free_notifier); 121 static BLOCKING_NOTIFIER_HEAD(munmap_notifier); 122 123 void profile_task_exit(struct task_struct * task) 124 { 125 blocking_notifier_call_chain(&task_exit_notifier, 0, task); 126 } 127 128 int profile_handoff_task(struct task_struct * task) 129 { 130 int ret; 131 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task); 132 return (ret == NOTIFY_OK) ? 1 : 0; 133 } 134 135 void profile_munmap(unsigned long addr) 136 { 137 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr); 138 } 139 140 int task_handoff_register(struct notifier_block * n) 141 { 142 return atomic_notifier_chain_register(&task_free_notifier, n); 143 } 144 145 int task_handoff_unregister(struct notifier_block * n) 146 { 147 return atomic_notifier_chain_unregister(&task_free_notifier, n); 148 } 149 150 int profile_event_register(enum profile_type type, struct notifier_block * n) 151 { 152 int err = -EINVAL; 153 154 switch (type) { 155 case PROFILE_TASK_EXIT: 156 err = blocking_notifier_chain_register( 157 &task_exit_notifier, n); 158 break; 159 case PROFILE_MUNMAP: 160 err = blocking_notifier_chain_register( 161 &munmap_notifier, n); 162 break; 163 } 164 165 return err; 166 } 167 168 169 int profile_event_unregister(enum profile_type type, struct notifier_block * n) 170 { 171 int err = -EINVAL; 172 173 switch (type) { 174 case PROFILE_TASK_EXIT: 175 err = blocking_notifier_chain_unregister( 176 &task_exit_notifier, n); 177 break; 178 case PROFILE_MUNMAP: 179 err = blocking_notifier_chain_unregister( 180 &munmap_notifier, n); 181 break; 182 } 183 184 return err; 185 } 186 187 int register_timer_hook(int (*hook)(struct pt_regs *)) 188 { 189 if (timer_hook) 190 return -EBUSY; 191 timer_hook = hook; 192 return 0; 193 } 194 195 void unregister_timer_hook(int (*hook)(struct pt_regs *)) 196 { 197 WARN_ON(hook != timer_hook); 198 timer_hook = NULL; 199 /* make sure all CPUs see the NULL hook */ 200 synchronize_sched(); /* Allow ongoing interrupts to complete. */ 201 } 202 203 EXPORT_SYMBOL_GPL(register_timer_hook); 204 EXPORT_SYMBOL_GPL(unregister_timer_hook); 205 EXPORT_SYMBOL_GPL(task_handoff_register); 206 EXPORT_SYMBOL_GPL(task_handoff_unregister); 207 EXPORT_SYMBOL_GPL(profile_event_register); 208 EXPORT_SYMBOL_GPL(profile_event_unregister); 209 210 #endif /* CONFIG_PROFILING */ 211 212 213 #ifdef CONFIG_SMP 214 /* 215 * Each cpu has a pair of open-addressed hashtables for pending 216 * profile hits. read_profile() IPI's all cpus to request them 217 * to flip buffers and flushes their contents to prof_buffer itself. 218 * Flip requests are serialized by the profile_flip_mutex. The sole 219 * use of having a second hashtable is for avoiding cacheline 220 * contention that would otherwise happen during flushes of pending 221 * profile hits required for the accuracy of reported profile hits 222 * and so resurrect the interrupt livelock issue. 223 * 224 * The open-addressed hashtables are indexed by profile buffer slot 225 * and hold the number of pending hits to that profile buffer slot on 226 * a cpu in an entry. When the hashtable overflows, all pending hits 227 * are accounted to their corresponding profile buffer slots with 228 * atomic_add() and the hashtable emptied. As numerous pending hits 229 * may be accounted to a profile buffer slot in a hashtable entry, 230 * this amortizes a number of atomic profile buffer increments likely 231 * to be far larger than the number of entries in the hashtable, 232 * particularly given that the number of distinct profile buffer 233 * positions to which hits are accounted during short intervals (e.g. 234 * several seconds) is usually very small. Exclusion from buffer 235 * flipping is provided by interrupt disablement (note that for 236 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from 237 * process context). 238 * The hash function is meant to be lightweight as opposed to strong, 239 * and was vaguely inspired by ppc64 firmware-supported inverted 240 * pagetable hash functions, but uses a full hashtable full of finite 241 * collision chains, not just pairs of them. 242 * 243 * -- wli 244 */ 245 static void __profile_flip_buffers(void *unused) 246 { 247 int cpu = smp_processor_id(); 248 249 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 250 } 251 252 static void profile_flip_buffers(void) 253 { 254 int i, j, cpu; 255 256 mutex_lock(&profile_flip_mutex); 257 j = per_cpu(cpu_profile_flip, get_cpu()); 258 put_cpu(); 259 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 260 for_each_online_cpu(cpu) { 261 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; 262 for (i = 0; i < NR_PROFILE_HIT; ++i) { 263 if (!hits[i].hits) { 264 if (hits[i].pc) 265 hits[i].pc = 0; 266 continue; 267 } 268 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 269 hits[i].hits = hits[i].pc = 0; 270 } 271 } 272 mutex_unlock(&profile_flip_mutex); 273 } 274 275 static void profile_discard_flip_buffers(void) 276 { 277 int i, cpu; 278 279 mutex_lock(&profile_flip_mutex); 280 i = per_cpu(cpu_profile_flip, get_cpu()); 281 put_cpu(); 282 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 283 for_each_online_cpu(cpu) { 284 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 285 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 286 } 287 mutex_unlock(&profile_flip_mutex); 288 } 289 290 void profile_hits(int type, void *__pc, unsigned int nr_hits) 291 { 292 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 293 int i, j, cpu; 294 struct profile_hit *hits; 295 296 if (prof_on != type || !prof_buffer) 297 return; 298 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1); 299 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 300 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 301 cpu = get_cpu(); 302 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)]; 303 if (!hits) { 304 put_cpu(); 305 return; 306 } 307 /* 308 * We buffer the global profiler buffer into a per-CPU 309 * queue and thus reduce the number of global (and possibly 310 * NUMA-alien) accesses. The write-queue is self-coalescing: 311 */ 312 local_irq_save(flags); 313 do { 314 for (j = 0; j < PROFILE_GRPSZ; ++j) { 315 if (hits[i + j].pc == pc) { 316 hits[i + j].hits += nr_hits; 317 goto out; 318 } else if (!hits[i + j].hits) { 319 hits[i + j].pc = pc; 320 hits[i + j].hits = nr_hits; 321 goto out; 322 } 323 } 324 i = (i + secondary) & (NR_PROFILE_HIT - 1); 325 } while (i != primary); 326 327 /* 328 * Add the current hit(s) and flush the write-queue out 329 * to the global buffer: 330 */ 331 atomic_add(nr_hits, &prof_buffer[pc]); 332 for (i = 0; i < NR_PROFILE_HIT; ++i) { 333 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 334 hits[i].pc = hits[i].hits = 0; 335 } 336 out: 337 local_irq_restore(flags); 338 put_cpu(); 339 } 340 341 static int __devinit profile_cpu_callback(struct notifier_block *info, 342 unsigned long action, void *__cpu) 343 { 344 int node, cpu = (unsigned long)__cpu; 345 struct page *page; 346 347 switch (action) { 348 case CPU_UP_PREPARE: 349 case CPU_UP_PREPARE_FROZEN: 350 node = cpu_to_node(cpu); 351 per_cpu(cpu_profile_flip, cpu) = 0; 352 if (!per_cpu(cpu_profile_hits, cpu)[1]) { 353 page = alloc_pages_node(node, 354 GFP_KERNEL | __GFP_ZERO, 355 0); 356 if (!page) 357 return NOTIFY_BAD; 358 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page); 359 } 360 if (!per_cpu(cpu_profile_hits, cpu)[0]) { 361 page = alloc_pages_node(node, 362 GFP_KERNEL | __GFP_ZERO, 363 0); 364 if (!page) 365 goto out_free; 366 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page); 367 } 368 break; 369 out_free: 370 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 371 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 372 __free_page(page); 373 return NOTIFY_BAD; 374 case CPU_ONLINE: 375 case CPU_ONLINE_FROZEN: 376 cpu_set(cpu, prof_cpu_mask); 377 break; 378 case CPU_UP_CANCELED: 379 case CPU_UP_CANCELED_FROZEN: 380 case CPU_DEAD: 381 case CPU_DEAD_FROZEN: 382 cpu_clear(cpu, prof_cpu_mask); 383 if (per_cpu(cpu_profile_hits, cpu)[0]) { 384 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 385 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 386 __free_page(page); 387 } 388 if (per_cpu(cpu_profile_hits, cpu)[1]) { 389 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 390 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 391 __free_page(page); 392 } 393 break; 394 } 395 return NOTIFY_OK; 396 } 397 #else /* !CONFIG_SMP */ 398 #define profile_flip_buffers() do { } while (0) 399 #define profile_discard_flip_buffers() do { } while (0) 400 #define profile_cpu_callback NULL 401 402 void profile_hits(int type, void *__pc, unsigned int nr_hits) 403 { 404 unsigned long pc; 405 406 if (prof_on != type || !prof_buffer) 407 return; 408 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 409 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); 410 } 411 #endif /* !CONFIG_SMP */ 412 413 EXPORT_SYMBOL_GPL(profile_hits); 414 415 void profile_tick(int type) 416 { 417 struct pt_regs *regs = get_irq_regs(); 418 419 if (type == CPU_PROFILING && timer_hook) 420 timer_hook(regs); 421 if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask)) 422 profile_hit(type, (void *)profile_pc(regs)); 423 } 424 425 #ifdef CONFIG_PROC_FS 426 #include <linux/proc_fs.h> 427 #include <asm/uaccess.h> 428 #include <asm/ptrace.h> 429 430 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off, 431 int count, int *eof, void *data) 432 { 433 int len = cpumask_scnprintf(page, count, *(cpumask_t *)data); 434 if (count - len < 2) 435 return -EINVAL; 436 len += sprintf(page + len, "\n"); 437 return len; 438 } 439 440 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer, 441 unsigned long count, void *data) 442 { 443 cpumask_t *mask = (cpumask_t *)data; 444 unsigned long full_count = count, err; 445 cpumask_t new_value; 446 447 err = cpumask_parse_user(buffer, count, new_value); 448 if (err) 449 return err; 450 451 *mask = new_value; 452 return full_count; 453 } 454 455 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir) 456 { 457 struct proc_dir_entry *entry; 458 459 /* create /proc/irq/prof_cpu_mask */ 460 if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir))) 461 return; 462 entry->data = (void *)&prof_cpu_mask; 463 entry->read_proc = prof_cpu_mask_read_proc; 464 entry->write_proc = prof_cpu_mask_write_proc; 465 } 466 467 /* 468 * This function accesses profiling information. The returned data is 469 * binary: the sampling step and the actual contents of the profile 470 * buffer. Use of the program readprofile is recommended in order to 471 * get meaningful info out of these data. 472 */ 473 static ssize_t 474 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos) 475 { 476 unsigned long p = *ppos; 477 ssize_t read; 478 char * pnt; 479 unsigned int sample_step = 1 << prof_shift; 480 481 profile_flip_buffers(); 482 if (p >= (prof_len+1)*sizeof(unsigned int)) 483 return 0; 484 if (count > (prof_len+1)*sizeof(unsigned int) - p) 485 count = (prof_len+1)*sizeof(unsigned int) - p; 486 read = 0; 487 488 while (p < sizeof(unsigned int) && count > 0) { 489 if (put_user(*((char *)(&sample_step)+p),buf)) 490 return -EFAULT; 491 buf++; p++; count--; read++; 492 } 493 pnt = (char *)prof_buffer + p - sizeof(atomic_t); 494 if (copy_to_user(buf,(void *)pnt,count)) 495 return -EFAULT; 496 read += count; 497 *ppos += read; 498 return read; 499 } 500 501 /* 502 * Writing to /proc/profile resets the counters 503 * 504 * Writing a 'profiling multiplier' value into it also re-sets the profiling 505 * interrupt frequency, on architectures that support this. 506 */ 507 static ssize_t write_profile(struct file *file, const char __user *buf, 508 size_t count, loff_t *ppos) 509 { 510 #ifdef CONFIG_SMP 511 extern int setup_profiling_timer (unsigned int multiplier); 512 513 if (count == sizeof(int)) { 514 unsigned int multiplier; 515 516 if (copy_from_user(&multiplier, buf, sizeof(int))) 517 return -EFAULT; 518 519 if (setup_profiling_timer(multiplier)) 520 return -EINVAL; 521 } 522 #endif 523 profile_discard_flip_buffers(); 524 memset(prof_buffer, 0, prof_len * sizeof(atomic_t)); 525 return count; 526 } 527 528 static const struct file_operations proc_profile_operations = { 529 .read = read_profile, 530 .write = write_profile, 531 }; 532 533 #ifdef CONFIG_SMP 534 static void __init profile_nop(void *unused) 535 { 536 } 537 538 static int __init create_hash_tables(void) 539 { 540 int cpu; 541 542 for_each_online_cpu(cpu) { 543 int node = cpu_to_node(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, 0, 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 static int __init create_proc_profile(void) 587 { 588 struct proc_dir_entry *entry; 589 590 if (!prof_on) 591 return 0; 592 if (create_hash_tables()) 593 return -1; 594 if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL))) 595 return 0; 596 entry->proc_fops = &proc_profile_operations; 597 entry->size = (1+prof_len) * sizeof(atomic_t); 598 hotcpu_notifier(profile_cpu_callback, 0); 599 return 0; 600 } 601 module_init(create_proc_profile); 602 #endif /* CONFIG_PROC_FS */ 603