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/config.h> 17 #include <linux/module.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/profile.h> 25 #include <linux/highmem.h> 26 #include <asm/sections.h> 27 #include <asm/semaphore.h> 28 29 struct profile_hit { 30 u32 pc, hits; 31 }; 32 #define PROFILE_GRPSHIFT 3 33 #define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT) 34 #define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit)) 35 #define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ) 36 37 /* Oprofile timer tick hook */ 38 int (*timer_hook)(struct pt_regs *) __read_mostly; 39 40 static atomic_t *prof_buffer; 41 static unsigned long prof_len, prof_shift; 42 static int prof_on __read_mostly; 43 static cpumask_t prof_cpu_mask = CPU_MASK_ALL; 44 #ifdef CONFIG_SMP 45 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits); 46 static DEFINE_PER_CPU(int, cpu_profile_flip); 47 static DECLARE_MUTEX(profile_flip_mutex); 48 #endif /* CONFIG_SMP */ 49 50 static int __init profile_setup(char * str) 51 { 52 static char __initdata schedstr[] = "schedule"; 53 int par; 54 55 if (!strncmp(str, schedstr, strlen(schedstr))) { 56 prof_on = SCHED_PROFILING; 57 if (str[strlen(schedstr)] == ',') 58 str += strlen(schedstr) + 1; 59 if (get_option(&str, &par)) 60 prof_shift = par; 61 printk(KERN_INFO 62 "kernel schedule profiling enabled (shift: %ld)\n", 63 prof_shift); 64 } else if (get_option(&str, &par)) { 65 prof_shift = par; 66 prof_on = CPU_PROFILING; 67 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n", 68 prof_shift); 69 } 70 return 1; 71 } 72 __setup("profile=", profile_setup); 73 74 75 void __init profile_init(void) 76 { 77 if (!prof_on) 78 return; 79 80 /* only text is profiled */ 81 prof_len = (_etext - _stext) >> prof_shift; 82 prof_buffer = alloc_bootmem(prof_len*sizeof(atomic_t)); 83 } 84 85 /* Profile event notifications */ 86 87 #ifdef CONFIG_PROFILING 88 89 static DECLARE_RWSEM(profile_rwsem); 90 static DEFINE_RWLOCK(handoff_lock); 91 static struct notifier_block * task_exit_notifier; 92 static struct notifier_block * task_free_notifier; 93 static struct notifier_block * munmap_notifier; 94 95 void profile_task_exit(struct task_struct * task) 96 { 97 down_read(&profile_rwsem); 98 notifier_call_chain(&task_exit_notifier, 0, task); 99 up_read(&profile_rwsem); 100 } 101 102 int profile_handoff_task(struct task_struct * task) 103 { 104 int ret; 105 read_lock(&handoff_lock); 106 ret = notifier_call_chain(&task_free_notifier, 0, task); 107 read_unlock(&handoff_lock); 108 return (ret == NOTIFY_OK) ? 1 : 0; 109 } 110 111 void profile_munmap(unsigned long addr) 112 { 113 down_read(&profile_rwsem); 114 notifier_call_chain(&munmap_notifier, 0, (void *)addr); 115 up_read(&profile_rwsem); 116 } 117 118 int task_handoff_register(struct notifier_block * n) 119 { 120 int err = -EINVAL; 121 122 write_lock(&handoff_lock); 123 err = notifier_chain_register(&task_free_notifier, n); 124 write_unlock(&handoff_lock); 125 return err; 126 } 127 128 int task_handoff_unregister(struct notifier_block * n) 129 { 130 int err = -EINVAL; 131 132 write_lock(&handoff_lock); 133 err = notifier_chain_unregister(&task_free_notifier, n); 134 write_unlock(&handoff_lock); 135 return err; 136 } 137 138 int profile_event_register(enum profile_type type, struct notifier_block * n) 139 { 140 int err = -EINVAL; 141 142 down_write(&profile_rwsem); 143 144 switch (type) { 145 case PROFILE_TASK_EXIT: 146 err = notifier_chain_register(&task_exit_notifier, n); 147 break; 148 case PROFILE_MUNMAP: 149 err = notifier_chain_register(&munmap_notifier, n); 150 break; 151 } 152 153 up_write(&profile_rwsem); 154 155 return err; 156 } 157 158 159 int profile_event_unregister(enum profile_type type, struct notifier_block * n) 160 { 161 int err = -EINVAL; 162 163 down_write(&profile_rwsem); 164 165 switch (type) { 166 case PROFILE_TASK_EXIT: 167 err = notifier_chain_unregister(&task_exit_notifier, n); 168 break; 169 case PROFILE_MUNMAP: 170 err = notifier_chain_unregister(&munmap_notifier, n); 171 break; 172 } 173 174 up_write(&profile_rwsem); 175 return err; 176 } 177 178 int register_timer_hook(int (*hook)(struct pt_regs *)) 179 { 180 if (timer_hook) 181 return -EBUSY; 182 timer_hook = hook; 183 return 0; 184 } 185 186 void unregister_timer_hook(int (*hook)(struct pt_regs *)) 187 { 188 WARN_ON(hook != timer_hook); 189 timer_hook = NULL; 190 /* make sure all CPUs see the NULL hook */ 191 synchronize_sched(); /* Allow ongoing interrupts to complete. */ 192 } 193 194 EXPORT_SYMBOL_GPL(register_timer_hook); 195 EXPORT_SYMBOL_GPL(unregister_timer_hook); 196 EXPORT_SYMBOL_GPL(task_handoff_register); 197 EXPORT_SYMBOL_GPL(task_handoff_unregister); 198 199 #endif /* CONFIG_PROFILING */ 200 201 EXPORT_SYMBOL_GPL(profile_event_register); 202 EXPORT_SYMBOL_GPL(profile_event_unregister); 203 204 #ifdef CONFIG_SMP 205 /* 206 * Each cpu has a pair of open-addressed hashtables for pending 207 * profile hits. read_profile() IPI's all cpus to request them 208 * to flip buffers and flushes their contents to prof_buffer itself. 209 * Flip requests are serialized by the profile_flip_mutex. The sole 210 * use of having a second hashtable is for avoiding cacheline 211 * contention that would otherwise happen during flushes of pending 212 * profile hits required for the accuracy of reported profile hits 213 * and so resurrect the interrupt livelock issue. 214 * 215 * The open-addressed hashtables are indexed by profile buffer slot 216 * and hold the number of pending hits to that profile buffer slot on 217 * a cpu in an entry. When the hashtable overflows, all pending hits 218 * are accounted to their corresponding profile buffer slots with 219 * atomic_add() and the hashtable emptied. As numerous pending hits 220 * may be accounted to a profile buffer slot in a hashtable entry, 221 * this amortizes a number of atomic profile buffer increments likely 222 * to be far larger than the number of entries in the hashtable, 223 * particularly given that the number of distinct profile buffer 224 * positions to which hits are accounted during short intervals (e.g. 225 * several seconds) is usually very small. Exclusion from buffer 226 * flipping is provided by interrupt disablement (note that for 227 * SCHED_PROFILING profile_hit() may be called from process context). 228 * The hash function is meant to be lightweight as opposed to strong, 229 * and was vaguely inspired by ppc64 firmware-supported inverted 230 * pagetable hash functions, but uses a full hashtable full of finite 231 * collision chains, not just pairs of them. 232 * 233 * -- wli 234 */ 235 static void __profile_flip_buffers(void *unused) 236 { 237 int cpu = smp_processor_id(); 238 239 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 240 } 241 242 static void profile_flip_buffers(void) 243 { 244 int i, j, cpu; 245 246 down(&profile_flip_mutex); 247 j = per_cpu(cpu_profile_flip, get_cpu()); 248 put_cpu(); 249 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 250 for_each_online_cpu(cpu) { 251 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; 252 for (i = 0; i < NR_PROFILE_HIT; ++i) { 253 if (!hits[i].hits) { 254 if (hits[i].pc) 255 hits[i].pc = 0; 256 continue; 257 } 258 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 259 hits[i].hits = hits[i].pc = 0; 260 } 261 } 262 up(&profile_flip_mutex); 263 } 264 265 static void profile_discard_flip_buffers(void) 266 { 267 int i, cpu; 268 269 down(&profile_flip_mutex); 270 i = per_cpu(cpu_profile_flip, get_cpu()); 271 put_cpu(); 272 on_each_cpu(__profile_flip_buffers, NULL, 0, 1); 273 for_each_online_cpu(cpu) { 274 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 275 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 276 } 277 up(&profile_flip_mutex); 278 } 279 280 void profile_hit(int type, void *__pc) 281 { 282 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 283 int i, j, cpu; 284 struct profile_hit *hits; 285 286 if (prof_on != type || !prof_buffer) 287 return; 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 local_irq_save(flags); 298 do { 299 for (j = 0; j < PROFILE_GRPSZ; ++j) { 300 if (hits[i + j].pc == pc) { 301 hits[i + j].hits++; 302 goto out; 303 } else if (!hits[i + j].hits) { 304 hits[i + j].pc = pc; 305 hits[i + j].hits = 1; 306 goto out; 307 } 308 } 309 i = (i + secondary) & (NR_PROFILE_HIT - 1); 310 } while (i != primary); 311 atomic_inc(&prof_buffer[pc]); 312 for (i = 0; i < NR_PROFILE_HIT; ++i) { 313 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 314 hits[i].pc = hits[i].hits = 0; 315 } 316 out: 317 local_irq_restore(flags); 318 put_cpu(); 319 } 320 321 #ifdef CONFIG_HOTPLUG_CPU 322 static int __devinit profile_cpu_callback(struct notifier_block *info, 323 unsigned long action, void *__cpu) 324 { 325 int node, cpu = (unsigned long)__cpu; 326 struct page *page; 327 328 switch (action) { 329 case CPU_UP_PREPARE: 330 node = cpu_to_node(cpu); 331 per_cpu(cpu_profile_flip, cpu) = 0; 332 if (!per_cpu(cpu_profile_hits, cpu)[1]) { 333 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); 334 if (!page) 335 return NOTIFY_BAD; 336 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page); 337 } 338 if (!per_cpu(cpu_profile_hits, cpu)[0]) { 339 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); 340 if (!page) 341 goto out_free; 342 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page); 343 } 344 break; 345 out_free: 346 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 347 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 348 __free_page(page); 349 return NOTIFY_BAD; 350 case CPU_ONLINE: 351 cpu_set(cpu, prof_cpu_mask); 352 break; 353 case CPU_UP_CANCELED: 354 case CPU_DEAD: 355 cpu_clear(cpu, prof_cpu_mask); 356 if (per_cpu(cpu_profile_hits, cpu)[0]) { 357 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 358 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 359 __free_page(page); 360 } 361 if (per_cpu(cpu_profile_hits, cpu)[1]) { 362 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 363 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 364 __free_page(page); 365 } 366 break; 367 } 368 return NOTIFY_OK; 369 } 370 #endif /* CONFIG_HOTPLUG_CPU */ 371 #else /* !CONFIG_SMP */ 372 #define profile_flip_buffers() do { } while (0) 373 #define profile_discard_flip_buffers() do { } while (0) 374 375 void profile_hit(int type, void *__pc) 376 { 377 unsigned long pc; 378 379 if (prof_on != type || !prof_buffer) 380 return; 381 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 382 atomic_inc(&prof_buffer[min(pc, prof_len - 1)]); 383 } 384 #endif /* !CONFIG_SMP */ 385 386 void profile_tick(int type, struct pt_regs *regs) 387 { 388 if (type == CPU_PROFILING && timer_hook) 389 timer_hook(regs); 390 if (!user_mode(regs) && cpu_isset(smp_processor_id(), prof_cpu_mask)) 391 profile_hit(type, (void *)profile_pc(regs)); 392 } 393 394 #ifdef CONFIG_PROC_FS 395 #include <linux/proc_fs.h> 396 #include <asm/uaccess.h> 397 #include <asm/ptrace.h> 398 399 static int prof_cpu_mask_read_proc (char *page, char **start, off_t off, 400 int count, int *eof, void *data) 401 { 402 int len = cpumask_scnprintf(page, count, *(cpumask_t *)data); 403 if (count - len < 2) 404 return -EINVAL; 405 len += sprintf(page + len, "\n"); 406 return len; 407 } 408 409 static int prof_cpu_mask_write_proc (struct file *file, const char __user *buffer, 410 unsigned long count, void *data) 411 { 412 cpumask_t *mask = (cpumask_t *)data; 413 unsigned long full_count = count, err; 414 cpumask_t new_value; 415 416 err = cpumask_parse(buffer, count, new_value); 417 if (err) 418 return err; 419 420 *mask = new_value; 421 return full_count; 422 } 423 424 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir) 425 { 426 struct proc_dir_entry *entry; 427 428 /* create /proc/irq/prof_cpu_mask */ 429 if (!(entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir))) 430 return; 431 entry->nlink = 1; 432 entry->data = (void *)&prof_cpu_mask; 433 entry->read_proc = prof_cpu_mask_read_proc; 434 entry->write_proc = prof_cpu_mask_write_proc; 435 } 436 437 /* 438 * This function accesses profiling information. The returned data is 439 * binary: the sampling step and the actual contents of the profile 440 * buffer. Use of the program readprofile is recommended in order to 441 * get meaningful info out of these data. 442 */ 443 static ssize_t 444 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos) 445 { 446 unsigned long p = *ppos; 447 ssize_t read; 448 char * pnt; 449 unsigned int sample_step = 1 << prof_shift; 450 451 profile_flip_buffers(); 452 if (p >= (prof_len+1)*sizeof(unsigned int)) 453 return 0; 454 if (count > (prof_len+1)*sizeof(unsigned int) - p) 455 count = (prof_len+1)*sizeof(unsigned int) - p; 456 read = 0; 457 458 while (p < sizeof(unsigned int) && count > 0) { 459 put_user(*((char *)(&sample_step)+p),buf); 460 buf++; p++; count--; read++; 461 } 462 pnt = (char *)prof_buffer + p - sizeof(atomic_t); 463 if (copy_to_user(buf,(void *)pnt,count)) 464 return -EFAULT; 465 read += count; 466 *ppos += read; 467 return read; 468 } 469 470 /* 471 * Writing to /proc/profile resets the counters 472 * 473 * Writing a 'profiling multiplier' value into it also re-sets the profiling 474 * interrupt frequency, on architectures that support this. 475 */ 476 static ssize_t write_profile(struct file *file, const char __user *buf, 477 size_t count, loff_t *ppos) 478 { 479 #ifdef CONFIG_SMP 480 extern int setup_profiling_timer (unsigned int multiplier); 481 482 if (count == sizeof(int)) { 483 unsigned int multiplier; 484 485 if (copy_from_user(&multiplier, buf, sizeof(int))) 486 return -EFAULT; 487 488 if (setup_profiling_timer(multiplier)) 489 return -EINVAL; 490 } 491 #endif 492 profile_discard_flip_buffers(); 493 memset(prof_buffer, 0, prof_len * sizeof(atomic_t)); 494 return count; 495 } 496 497 static struct file_operations proc_profile_operations = { 498 .read = read_profile, 499 .write = write_profile, 500 }; 501 502 #ifdef CONFIG_SMP 503 static void __init profile_nop(void *unused) 504 { 505 } 506 507 static int __init create_hash_tables(void) 508 { 509 int cpu; 510 511 for_each_online_cpu(cpu) { 512 int node = cpu_to_node(cpu); 513 struct page *page; 514 515 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); 516 if (!page) 517 goto out_cleanup; 518 per_cpu(cpu_profile_hits, cpu)[1] 519 = (struct profile_hit *)page_address(page); 520 page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); 521 if (!page) 522 goto out_cleanup; 523 per_cpu(cpu_profile_hits, cpu)[0] 524 = (struct profile_hit *)page_address(page); 525 } 526 return 0; 527 out_cleanup: 528 prof_on = 0; 529 smp_mb(); 530 on_each_cpu(profile_nop, NULL, 0, 1); 531 for_each_online_cpu(cpu) { 532 struct page *page; 533 534 if (per_cpu(cpu_profile_hits, cpu)[0]) { 535 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 536 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 537 __free_page(page); 538 } 539 if (per_cpu(cpu_profile_hits, cpu)[1]) { 540 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 541 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 542 __free_page(page); 543 } 544 } 545 return -1; 546 } 547 #else 548 #define create_hash_tables() ({ 0; }) 549 #endif 550 551 static int __init create_proc_profile(void) 552 { 553 struct proc_dir_entry *entry; 554 555 if (!prof_on) 556 return 0; 557 if (create_hash_tables()) 558 return -1; 559 if (!(entry = create_proc_entry("profile", S_IWUSR | S_IRUGO, NULL))) 560 return 0; 561 entry->proc_fops = &proc_profile_operations; 562 entry->size = (1+prof_len) * sizeof(atomic_t); 563 hotcpu_notifier(profile_cpu_callback, 0); 564 return 0; 565 } 566 module_init(create_proc_profile); 567 #endif /* CONFIG_PROC_FS */ 568