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 30 struct profile_hit { 31 u32 pc, hits; 32 }; 33 #define PROFILE_GRPSHIFT 3 34 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT) 35 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit)) 36 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ) 37 38 /* Oprofile timer tick hook */ 39 int (*timer_hook)(struct pt_regs *) __read_mostly; 40 41 static atomic_t *prof_buffer; 42 static unsigned long prof_len, prof_shift; 43 44 int prof_on __read_mostly; 45 EXPORT_SYMBOL_GPL(prof_on); 46 47 static cpumask_t prof_cpu_mask = CPU_MASK_ALL; 48 #ifdef CONFIG_SMP 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 static int __init profile_setup(char * str) 55 { 56 static char __initdata schedstr[] = "schedule"; 57 static char __initdata sleepstr[] = "sleep"; 58 static char __initdata kvmstr[] = "kvm"; 59 int par; 60 61 if (!strncmp(str, sleepstr, strlen(sleepstr))) { 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 printk(KERN_INFO 68 "kernel sleep profiling enabled (shift: %ld)\n", 69 prof_shift); 70 } else if (!strncmp(str, schedstr, strlen(schedstr))) { 71 prof_on = SCHED_PROFILING; 72 if (str[strlen(schedstr)] == ',') 73 str += strlen(schedstr) + 1; 74 if (get_option(&str, &par)) 75 prof_shift = par; 76 printk(KERN_INFO 77 "kernel schedule profiling enabled (shift: %ld)\n", 78 prof_shift); 79 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) { 80 prof_on = KVM_PROFILING; 81 if (str[strlen(kvmstr)] == ',') 82 str += strlen(kvmstr) + 1; 83 if (get_option(&str, &par)) 84 prof_shift = par; 85 printk(KERN_INFO 86 "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 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n", 92 prof_shift); 93 } 94 return 1; 95 } 96 __setup("profile=", profile_setup); 97 98 99 void __init profile_init(void) 100 { 101 if (!prof_on) 102 return; 103 104 /* only text is profiled */ 105 prof_len = (_etext - _stext) >> prof_shift; 106 prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t)); 107 } 108 109 /* Profile event notifications */ 110 111 #ifdef CONFIG_PROFILING 112 113 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier); 114 static ATOMIC_NOTIFIER_HEAD(task_free_notifier); 115 static BLOCKING_NOTIFIER_HEAD(munmap_notifier); 116 117 void profile_task_exit(struct task_struct * task) 118 { 119 blocking_notifier_call_chain(&task_exit_notifier, 0, task); 120 } 121 122 int profile_handoff_task(struct task_struct * task) 123 { 124 int ret; 125 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task); 126 return (ret == NOTIFY_OK) ? 1 : 0; 127 } 128 129 void profile_munmap(unsigned long addr) 130 { 131 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr); 132 } 133 134 int task_handoff_register(struct notifier_block * n) 135 { 136 return atomic_notifier_chain_register(&task_free_notifier, n); 137 } 138 139 int task_handoff_unregister(struct notifier_block * n) 140 { 141 return atomic_notifier_chain_unregister(&task_free_notifier, n); 142 } 143 144 int profile_event_register(enum profile_type type, struct notifier_block * n) 145 { 146 int err = -EINVAL; 147 148 switch (type) { 149 case PROFILE_TASK_EXIT: 150 err = blocking_notifier_chain_register( 151 &task_exit_notifier, n); 152 break; 153 case PROFILE_MUNMAP: 154 err = blocking_notifier_chain_register( 155 &munmap_notifier, n); 156 break; 157 } 158 159 return err; 160 } 161 162 163 int profile_event_unregister(enum profile_type type, struct notifier_block * n) 164 { 165 int err = -EINVAL; 166 167 switch (type) { 168 case PROFILE_TASK_EXIT: 169 err = blocking_notifier_chain_unregister( 170 &task_exit_notifier, n); 171 break; 172 case PROFILE_MUNMAP: 173 err = blocking_notifier_chain_unregister( 174 &munmap_notifier, n); 175 break; 176 } 177 178 return err; 179 } 180 181 int register_timer_hook(int (*hook)(struct pt_regs *)) 182 { 183 if (timer_hook) 184 return -EBUSY; 185 timer_hook = hook; 186 return 0; 187 } 188 189 void unregister_timer_hook(int (*hook)(struct pt_regs *)) 190 { 191 WARN_ON(hook != timer_hook); 192 timer_hook = NULL; 193 /* make sure all CPUs see the NULL hook */ 194 synchronize_sched(); /* Allow ongoing interrupts to complete. */ 195 } 196 197 EXPORT_SYMBOL_GPL(register_timer_hook); 198 EXPORT_SYMBOL_GPL(unregister_timer_hook); 199 EXPORT_SYMBOL_GPL(task_handoff_register); 200 EXPORT_SYMBOL_GPL(task_handoff_unregister); 201 202 #endif /* CONFIG_PROFILING */ 203 204 EXPORT_SYMBOL_GPL(profile_event_register); 205 EXPORT_SYMBOL_GPL(profile_event_unregister); 206 207 #ifdef CONFIG_SMP 208 /* 209 * Each cpu has a pair of open-addressed hashtables for pending 210 * profile hits. read_profile() IPI's all cpus to request them 211 * to flip buffers and flushes their contents to prof_buffer itself. 212 * Flip requests are serialized by the profile_flip_mutex. The sole 213 * use of having a second hashtable is for avoiding cacheline 214 * contention that would otherwise happen during flushes of pending 215 * profile hits required for the accuracy of reported profile hits 216 * and so resurrect the interrupt livelock issue. 217 * 218 * The open-addressed hashtables are indexed by profile buffer slot 219 * and hold the number of pending hits to that profile buffer slot on 220 * a cpu in an entry. When the hashtable overflows, all pending hits 221 * are accounted to their corresponding profile buffer slots with 222 * atomic_add() and the hashtable emptied. As numerous pending hits 223 * may be accounted to a profile buffer slot in a hashtable entry, 224 * this amortizes a number of atomic profile buffer increments likely 225 * to be far larger than the number of entries in the hashtable, 226 * particularly given that the number of distinct profile buffer 227 * positions to which hits are accounted during short intervals (e.g. 228 * several seconds) is usually very small. Exclusion from buffer 229 * flipping is provided by interrupt disablement (note that for 230 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from 231 * process context). 232 * The hash function is meant to be lightweight as opposed to strong, 233 * and was vaguely inspired by ppc64 firmware-supported inverted 234 * pagetable hash functions, but uses a full hashtable full of finite 235 * collision chains, not just pairs of them. 236 * 237 * -- wli 238 */ 239 static void __profile_flip_buffers(void *unused) 240 { 241 int cpu = smp_processor_id(); 242 243 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 244 } 245 246 static void profile_flip_buffers(void) 247 { 248 int i, j, cpu; 249 250 mutex_lock(&profile_flip_mutex); 251 j = per_cpu(cpu_profile_flip, get_cpu()); 252 put_cpu(); 253 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 254 for_each_online_cpu(cpu) { 255 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; 256 for (i = 0; i < NR_PROFILE_HIT; ++i) { 257 if (!hits[i].hits) { 258 if (hits[i].pc) 259 hits[i].pc = 0; 260 continue; 261 } 262 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 263 hits[i].hits = hits[i].pc = 0; 264 } 265 } 266 mutex_unlock(&profile_flip_mutex); 267 } 268 269 static void profile_discard_flip_buffers(void) 270 { 271 int i, cpu; 272 273 mutex_lock(&profile_flip_mutex); 274 i = per_cpu(cpu_profile_flip, get_cpu()); 275 put_cpu(); 276 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 277 for_each_online_cpu(cpu) { 278 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 279 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 280 } 281 mutex_unlock(&profile_flip_mutex); 282 } 283 284 void profile_hits(int type, void *__pc, unsigned int nr_hits) 285 { 286 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 287 int i, j, cpu; 288 struct profile_hit *hits; 289 290 if (prof_on != type || !prof_buffer) 291 return; 292 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1); 293 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 294 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 295 cpu = get_cpu(); 296 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)]; 297 if (!hits) { 298 put_cpu(); 299 return; 300 } 301 /* 302 * We buffer the global profiler buffer into a per-CPU 303 * queue and thus reduce the number of global (and possibly 304 * NUMA-alien) accesses. The write-queue is self-coalescing: 305 */ 306 local_irq_save(flags); 307 do { 308 for (j = 0; j < PROFILE_GRPSZ; ++j) { 309 if (hits[i + j].pc == pc) { 310 hits[i + j].hits += nr_hits; 311 goto out; 312 } else if (!hits[i + j].hits) { 313 hits[i + j].pc = pc; 314 hits[i + j].hits = nr_hits; 315 goto out; 316 } 317 } 318 i = (i + secondary) & (NR_PROFILE_HIT - 1); 319 } while (i != primary); 320 321 /* 322 * Add the current hit(s) and flush the write-queue out 323 * to the global buffer: 324 */ 325 atomic_add(nr_hits, &prof_buffer[pc]); 326 for (i = 0; i < NR_PROFILE_HIT; ++i) { 327 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 328 hits[i].pc = hits[i].hits = 0; 329 } 330 out: 331 local_irq_restore(flags); 332 put_cpu(); 333 } 334 335 static int __devinit profile_cpu_callback(struct notifier_block *info, 336 unsigned long action, void *__cpu) 337 { 338 int node, cpu = (unsigned long)__cpu; 339 struct page *page; 340 341 switch (action) { 342 case CPU_UP_PREPARE: 343 node = cpu_to_node(cpu); 344 per_cpu(cpu_profile_flip, cpu) = 0; 345 if (!per_cpu(cpu_profile_hits, cpu)[1]) { 346 page = alloc_pages_node(node, 347 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 348 0); 349 if (!page) 350 return NOTIFY_BAD; 351 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page); 352 } 353 if (!per_cpu(cpu_profile_hits, cpu)[0]) { 354 page = alloc_pages_node(node, 355 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 356 0); 357 if (!page) 358 goto out_free; 359 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page); 360 } 361 break; 362 out_free: 363 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 364 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 365 __free_page(page); 366 return NOTIFY_BAD; 367 case CPU_ONLINE: 368 cpu_set(cpu, prof_cpu_mask); 369 break; 370 case CPU_UP_CANCELED: 371 case CPU_DEAD: 372 cpu_clear(cpu, prof_cpu_mask); 373 if (per_cpu(cpu_profile_hits, cpu)[0]) { 374 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 375 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 376 __free_page(page); 377 } 378 if (per_cpu(cpu_profile_hits, cpu)[1]) { 379 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 380 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 381 __free_page(page); 382 } 383 break; 384 } 385 return NOTIFY_OK; 386 } 387 #else /* !CONFIG_SMP */ 388 #define profile_flip_buffers() do { } while (0) 389 #define profile_discard_flip_buffers() do { } while (0) 390 #define profile_cpu_callback NULL 391 392 void profile_hits(int type, void *__pc, unsigned int nr_hits) 393 { 394 unsigned long pc; 395 396 if (prof_on != type || !prof_buffer) 397 return; 398 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 399 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); 400 } 401 #endif /* !CONFIG_SMP */ 402 403 EXPORT_SYMBOL_GPL(profile_hits); 404 405 void profile_tick(int type) 406 { 407 struct pt_regs *regs = get_irq_regs(); 408 409 if (type == CPU_PROFILING && timer_hook) 410 timer_hook(regs); 411 if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask)) 412 profile_hit(type, (void *)profile_pc(regs)); 413 } 414 415 #ifdef CONFIG_PROC_FS 416 #include <linux/proc_fs.h> 417 #include <asm/uaccess.h> 418 #include <asm/ptrace.h> 419 420 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off, 421 int count, int *eof, void *data) 422 { 423 int len = cpumask_scnprintf(page, count, *(cpumask_t *)data); 424 if (count - len < 2) 425 return -EINVAL; 426 len += sprintf(page + len, "\n"); 427 return len; 428 } 429 430 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer, 431 unsigned long count, void *data) 432 { 433 cpumask_t *mask = (cpumask_t *)data; 434 unsigned long full_count = count, err; 435 cpumask_t new_value; 436 437 err = cpumask_parse_user(buffer, count, new_value); 438 if (err) 439 return err; 440 441 *mask = new_value; 442 return full_count; 443 } 444 445 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir) 446 { 447 struct proc_dir_entry *entry; 448 449 /* create /proc/irq/prof_cpu_mask */ 450 if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir))) 451 return; 452 entry->data = (void *)&prof_cpu_mask; 453 entry->read_proc = prof_cpu_mask_read_proc; 454 entry->write_proc = prof_cpu_mask_write_proc; 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 int sample_step = 1 << 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 }; 522 523 #ifdef CONFIG_SMP 524 static void __init profile_nop(void *unused) 525 { 526 } 527 528 static int __init create_hash_tables(void) 529 { 530 int cpu; 531 532 for_each_online_cpu(cpu) { 533 int node = cpu_to_node(cpu); 534 struct page *page; 535 536 page = alloc_pages_node(node, 537 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 538 0); 539 if (!page) 540 goto out_cleanup; 541 per_cpu(cpu_profile_hits, cpu)[1] 542 = (struct profile_hit *)page_address(page); 543 page = alloc_pages_node(node, 544 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE, 545 0); 546 if (!page) 547 goto out_cleanup; 548 per_cpu(cpu_profile_hits, cpu)[0] 549 = (struct profile_hit *)page_address(page); 550 } 551 return 0; 552 out_cleanup: 553 prof_on = 0; 554 smp_mb(); 555 on_each_cpu(profile_nop, NULL, 0, 1); 556 for_each_online_cpu(cpu) { 557 struct page *page; 558 559 if (per_cpu(cpu_profile_hits, cpu)[0]) { 560 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 561 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 562 __free_page(page); 563 } 564 if (per_cpu(cpu_profile_hits, cpu)[1]) { 565 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 566 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 567 __free_page(page); 568 } 569 } 570 return -1; 571 } 572 #else 573 #define create_hash_tables() ({ 0; }) 574 #endif 575 576 static int __init create_proc_profile(void) 577 { 578 struct proc_dir_entry *entry; 579 580 if (!prof_on) 581 return 0; 582 if (create_hash_tables()) 583 return -1; 584 if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL))) 585 return 0; 586 entry->proc_fops = &proc_profile_operations; 587 entry->size = (1+prof_len) * sizeof(atomic_t); 588 hotcpu_notifier(profile_cpu_callback, 0); 589 return 0; 590 } 591 module_init(create_proc_profile); 592 #endif /* CONFIG_PROC_FS */ 593