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 #ifdef CONFIG_SMP 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 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 pr_info("kernel sleep profiling enabled (shift: %ld)\n", 68 prof_shift); 69 #else 70 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n"); 71 #endif /* CONFIG_SCHEDSTATS */ 72 } else if (!strncmp(str, schedstr, strlen(schedstr))) { 73 prof_on = SCHED_PROFILING; 74 if (str[strlen(schedstr)] == ',') 75 str += strlen(schedstr) + 1; 76 if (get_option(&str, &par)) 77 prof_shift = par; 78 pr_info("kernel schedule profiling enabled (shift: %ld)\n", 79 prof_shift); 80 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) { 81 prof_on = KVM_PROFILING; 82 if (str[strlen(kvmstr)] == ',') 83 str += strlen(kvmstr) + 1; 84 if (get_option(&str, &par)) 85 prof_shift = par; 86 pr_info("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 pr_info("kernel profiling enabled (shift: %ld)\n", 92 prof_shift); 93 } 94 return 1; 95 } 96 __setup("profile=", profile_setup); 97 98 99 int __ref profile_init(void) 100 { 101 int buffer_bytes; 102 if (!prof_on) 103 return 0; 104 105 /* only text is profiled */ 106 prof_len = (_etext - _stext) >> prof_shift; 107 buffer_bytes = prof_len*sizeof(atomic_t); 108 109 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL)) 110 return -ENOMEM; 111 112 cpumask_copy(prof_cpu_mask, cpu_possible_mask); 113 114 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN); 115 if (prof_buffer) 116 return 0; 117 118 prof_buffer = alloc_pages_exact(buffer_bytes, 119 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN); 120 if (prof_buffer) 121 return 0; 122 123 prof_buffer = vzalloc(buffer_bytes); 124 if (prof_buffer) 125 return 0; 126 127 free_cpumask_var(prof_cpu_mask); 128 return -ENOMEM; 129 } 130 131 /* Profile event notifications */ 132 133 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier); 134 static ATOMIC_NOTIFIER_HEAD(task_free_notifier); 135 static BLOCKING_NOTIFIER_HEAD(munmap_notifier); 136 137 void profile_task_exit(struct task_struct *task) 138 { 139 blocking_notifier_call_chain(&task_exit_notifier, 0, task); 140 } 141 142 int profile_handoff_task(struct task_struct *task) 143 { 144 int ret; 145 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task); 146 return (ret == NOTIFY_OK) ? 1 : 0; 147 } 148 149 void profile_munmap(unsigned long addr) 150 { 151 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr); 152 } 153 154 int task_handoff_register(struct notifier_block *n) 155 { 156 return atomic_notifier_chain_register(&task_free_notifier, n); 157 } 158 EXPORT_SYMBOL_GPL(task_handoff_register); 159 160 int task_handoff_unregister(struct notifier_block *n) 161 { 162 return atomic_notifier_chain_unregister(&task_free_notifier, n); 163 } 164 EXPORT_SYMBOL_GPL(task_handoff_unregister); 165 166 int profile_event_register(enum profile_type type, struct notifier_block *n) 167 { 168 int err = -EINVAL; 169 170 switch (type) { 171 case PROFILE_TASK_EXIT: 172 err = blocking_notifier_chain_register( 173 &task_exit_notifier, n); 174 break; 175 case PROFILE_MUNMAP: 176 err = blocking_notifier_chain_register( 177 &munmap_notifier, n); 178 break; 179 } 180 181 return err; 182 } 183 EXPORT_SYMBOL_GPL(profile_event_register); 184 185 int profile_event_unregister(enum profile_type type, struct notifier_block *n) 186 { 187 int err = -EINVAL; 188 189 switch (type) { 190 case PROFILE_TASK_EXIT: 191 err = blocking_notifier_chain_unregister( 192 &task_exit_notifier, n); 193 break; 194 case PROFILE_MUNMAP: 195 err = blocking_notifier_chain_unregister( 196 &munmap_notifier, n); 197 break; 198 } 199 200 return err; 201 } 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 or SLEEP_PROFILING profile_hit() may be called from 228 * process context). 229 * The hash function is meant to be lightweight as opposed to strong, 230 * and was vaguely inspired by ppc64 firmware-supported inverted 231 * pagetable hash functions, but uses a full hashtable full of finite 232 * collision chains, not just pairs of them. 233 * 234 * -- nyc 235 */ 236 static void __profile_flip_buffers(void *unused) 237 { 238 int cpu = smp_processor_id(); 239 240 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu); 241 } 242 243 static void profile_flip_buffers(void) 244 { 245 int i, j, cpu; 246 247 mutex_lock(&profile_flip_mutex); 248 j = per_cpu(cpu_profile_flip, get_cpu()); 249 put_cpu(); 250 on_each_cpu(__profile_flip_buffers, NULL, 1); 251 for_each_online_cpu(cpu) { 252 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j]; 253 for (i = 0; i < NR_PROFILE_HIT; ++i) { 254 if (!hits[i].hits) { 255 if (hits[i].pc) 256 hits[i].pc = 0; 257 continue; 258 } 259 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 260 hits[i].hits = hits[i].pc = 0; 261 } 262 } 263 mutex_unlock(&profile_flip_mutex); 264 } 265 266 static void profile_discard_flip_buffers(void) 267 { 268 int i, cpu; 269 270 mutex_lock(&profile_flip_mutex); 271 i = per_cpu(cpu_profile_flip, get_cpu()); 272 put_cpu(); 273 on_each_cpu(__profile_flip_buffers, NULL, 1); 274 for_each_online_cpu(cpu) { 275 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i]; 276 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit)); 277 } 278 mutex_unlock(&profile_flip_mutex); 279 } 280 281 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) 282 { 283 unsigned long primary, secondary, flags, pc = (unsigned long)__pc; 284 int i, j, cpu; 285 struct profile_hit *hits; 286 287 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1); 288 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 289 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT; 290 cpu = get_cpu(); 291 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)]; 292 if (!hits) { 293 put_cpu(); 294 return; 295 } 296 /* 297 * We buffer the global profiler buffer into a per-CPU 298 * queue and thus reduce the number of global (and possibly 299 * NUMA-alien) accesses. The write-queue is self-coalescing: 300 */ 301 local_irq_save(flags); 302 do { 303 for (j = 0; j < PROFILE_GRPSZ; ++j) { 304 if (hits[i + j].pc == pc) { 305 hits[i + j].hits += nr_hits; 306 goto out; 307 } else if (!hits[i + j].hits) { 308 hits[i + j].pc = pc; 309 hits[i + j].hits = nr_hits; 310 goto out; 311 } 312 } 313 i = (i + secondary) & (NR_PROFILE_HIT - 1); 314 } while (i != primary); 315 316 /* 317 * Add the current hit(s) and flush the write-queue out 318 * to the global buffer: 319 */ 320 atomic_add(nr_hits, &prof_buffer[pc]); 321 for (i = 0; i < NR_PROFILE_HIT; ++i) { 322 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]); 323 hits[i].pc = hits[i].hits = 0; 324 } 325 out: 326 local_irq_restore(flags); 327 put_cpu(); 328 } 329 330 static int profile_cpu_callback(struct notifier_block *info, 331 unsigned long action, void *__cpu) 332 { 333 int node, cpu = (unsigned long)__cpu; 334 struct page *page; 335 336 switch (action) { 337 case CPU_UP_PREPARE: 338 case CPU_UP_PREPARE_FROZEN: 339 node = cpu_to_mem(cpu); 340 per_cpu(cpu_profile_flip, cpu) = 0; 341 if (!per_cpu(cpu_profile_hits, cpu)[1]) { 342 page = __alloc_pages_node(node, 343 GFP_KERNEL | __GFP_ZERO, 344 0); 345 if (!page) 346 return notifier_from_errno(-ENOMEM); 347 per_cpu(cpu_profile_hits, cpu)[1] = page_address(page); 348 } 349 if (!per_cpu(cpu_profile_hits, cpu)[0]) { 350 page = __alloc_pages_node(node, 351 GFP_KERNEL | __GFP_ZERO, 352 0); 353 if (!page) 354 goto out_free; 355 per_cpu(cpu_profile_hits, cpu)[0] = page_address(page); 356 } 357 break; 358 out_free: 359 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 360 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 361 __free_page(page); 362 return notifier_from_errno(-ENOMEM); 363 case CPU_ONLINE: 364 case CPU_ONLINE_FROZEN: 365 if (prof_cpu_mask != NULL) 366 cpumask_set_cpu(cpu, prof_cpu_mask); 367 break; 368 case CPU_UP_CANCELED: 369 case CPU_UP_CANCELED_FROZEN: 370 case CPU_DEAD: 371 case CPU_DEAD_FROZEN: 372 if (prof_cpu_mask != NULL) 373 cpumask_clear_cpu(cpu, prof_cpu_mask); 374 if (per_cpu(cpu_profile_hits, cpu)[0]) { 375 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]); 376 per_cpu(cpu_profile_hits, cpu)[0] = NULL; 377 __free_page(page); 378 } 379 if (per_cpu(cpu_profile_hits, cpu)[1]) { 380 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]); 381 per_cpu(cpu_profile_hits, cpu)[1] = NULL; 382 __free_page(page); 383 } 384 break; 385 } 386 return NOTIFY_OK; 387 } 388 #else /* !CONFIG_SMP */ 389 #define profile_flip_buffers() do { } while (0) 390 #define profile_discard_flip_buffers() do { } while (0) 391 #define profile_cpu_callback NULL 392 393 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits) 394 { 395 unsigned long pc; 396 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift; 397 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]); 398 } 399 #endif /* !CONFIG_SMP */ 400 401 void profile_hits(int type, void *__pc, unsigned int nr_hits) 402 { 403 if (prof_on != type || !prof_buffer) 404 return; 405 do_profile_hits(type, __pc, nr_hits); 406 } 407 EXPORT_SYMBOL_GPL(profile_hits); 408 409 void profile_tick(int type) 410 { 411 struct pt_regs *regs = get_irq_regs(); 412 413 if (!user_mode(regs) && prof_cpu_mask != NULL && 414 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask)) 415 profile_hit(type, (void *)profile_pc(regs)); 416 } 417 418 #ifdef CONFIG_PROC_FS 419 #include <linux/proc_fs.h> 420 #include <linux/seq_file.h> 421 #include <asm/uaccess.h> 422 423 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v) 424 { 425 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask)); 426 return 0; 427 } 428 429 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file) 430 { 431 return single_open(file, prof_cpu_mask_proc_show, NULL); 432 } 433 434 static ssize_t prof_cpu_mask_proc_write(struct file *file, 435 const char __user *buffer, size_t count, loff_t *pos) 436 { 437 cpumask_var_t new_value; 438 int err; 439 440 if (!alloc_cpumask_var(&new_value, GFP_KERNEL)) 441 return -ENOMEM; 442 443 err = cpumask_parse_user(buffer, count, new_value); 444 if (!err) { 445 cpumask_copy(prof_cpu_mask, new_value); 446 err = count; 447 } 448 free_cpumask_var(new_value); 449 return err; 450 } 451 452 static const struct file_operations prof_cpu_mask_proc_fops = { 453 .open = prof_cpu_mask_proc_open, 454 .read = seq_read, 455 .llseek = seq_lseek, 456 .release = single_release, 457 .write = prof_cpu_mask_proc_write, 458 }; 459 460 void create_prof_cpu_mask(void) 461 { 462 /* create /proc/irq/prof_cpu_mask */ 463 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops); 464 } 465 466 /* 467 * This function accesses profiling information. The returned data is 468 * binary: the sampling step and the actual contents of the profile 469 * buffer. Use of the program readprofile is recommended in order to 470 * get meaningful info out of these data. 471 */ 472 static ssize_t 473 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos) 474 { 475 unsigned long p = *ppos; 476 ssize_t read; 477 char *pnt; 478 unsigned int sample_step = 1 << prof_shift; 479 480 profile_flip_buffers(); 481 if (p >= (prof_len+1)*sizeof(unsigned int)) 482 return 0; 483 if (count > (prof_len+1)*sizeof(unsigned int) - p) 484 count = (prof_len+1)*sizeof(unsigned int) - p; 485 read = 0; 486 487 while (p < sizeof(unsigned int) && count > 0) { 488 if (put_user(*((char *)(&sample_step)+p), buf)) 489 return -EFAULT; 490 buf++; p++; count--; read++; 491 } 492 pnt = (char *)prof_buffer + p - sizeof(atomic_t); 493 if (copy_to_user(buf, (void *)pnt, count)) 494 return -EFAULT; 495 read += count; 496 *ppos += read; 497 return read; 498 } 499 500 /* 501 * Writing to /proc/profile resets the counters 502 * 503 * Writing a 'profiling multiplier' value into it also re-sets the profiling 504 * interrupt frequency, on architectures that support this. 505 */ 506 static ssize_t write_profile(struct file *file, const char __user *buf, 507 size_t count, loff_t *ppos) 508 { 509 #ifdef CONFIG_SMP 510 extern int setup_profiling_timer(unsigned int multiplier); 511 512 if (count == sizeof(int)) { 513 unsigned int multiplier; 514 515 if (copy_from_user(&multiplier, buf, sizeof(int))) 516 return -EFAULT; 517 518 if (setup_profiling_timer(multiplier)) 519 return -EINVAL; 520 } 521 #endif 522 profile_discard_flip_buffers(); 523 memset(prof_buffer, 0, prof_len * sizeof(atomic_t)); 524 return count; 525 } 526 527 static const struct file_operations proc_profile_operations = { 528 .read = read_profile, 529 .write = write_profile, 530 .llseek = default_llseek, 531 }; 532 533 #ifdef CONFIG_SMP 534 static void profile_nop(void *unused) 535 { 536 } 537 538 static int create_hash_tables(void) 539 { 540 int cpu; 541 542 for_each_online_cpu(cpu) { 543 int node = cpu_to_mem(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, 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 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */ 587 { 588 struct proc_dir_entry *entry; 589 int err = 0; 590 591 if (!prof_on) 592 return 0; 593 594 cpu_notifier_register_begin(); 595 596 if (create_hash_tables()) { 597 err = -ENOMEM; 598 goto out; 599 } 600 601 entry = proc_create("profile", S_IWUSR | S_IRUGO, 602 NULL, &proc_profile_operations); 603 if (!entry) 604 goto out; 605 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t)); 606 __hotcpu_notifier(profile_cpu_callback, 0); 607 608 out: 609 cpu_notifier_register_done(); 610 return err; 611 } 612 subsys_initcall(create_proc_profile); 613 #endif /* CONFIG_PROC_FS */ 614