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