tools/perf/builtin-top.c

   1 /*
   2  * builtin-top.c
   3  *
   4  * Builtin top command: Display a continuously updated profile of
   5  * any workload, CPU or specific PID.
   6  *
   7  * Copyright (C) 2008, Red Hat Inc, Ingo Molnar <mingo@redhat.com>
   8  *
   9  * Improvements and fixes by:
  10  *
  11  *   Arjan van de Ven <arjan@linux.intel.com>
  12  *   Yanmin Zhang <yanmin.zhang@intel.com>
  13  *   Wu Fengguang <fengguang.wu@intel.com>
  14  *   Mike Galbraith <efault@gmx.de>
  15  *   Paul Mackerras <paulus@samba.org>
  16  *
  17  * Released under the GPL v2. (and only v2, not any later version)
  18  */
  19 #include "builtin.h"
  20
  21 #include "perf.h"
  22
  23 #include "util/symbol.h"
  24 #include "util/color.h"
  25 #include "util/util.h"
  26 #include <linux/rbtree.h>
  27 #include "util/parse-options.h"
  28 #include "util/parse-events.h"
  29
  30 #include <assert.h>
  31 #include <fcntl.h>
  32
  33 #include <stdio.h>
  34
  35 #include <errno.h>
  36 #include <time.h>
  37 #include <sched.h>
  38 #include <pthread.h>
  39
  40 #include <sys/syscall.h>
  41 #include <sys/ioctl.h>
  42 #include <sys/poll.h>
  43 #include <sys/prctl.h>
  44 #include <sys/wait.h>
  45 #include <sys/uio.h>
  46 #include <sys/mman.h>
  47
  48 #include <linux/unistd.h>
  49 #include <linux/types.h>
  50
  51 static int                      fd[MAX_NR_CPUS][MAX_COUNTERS];
  52
  53 static int                      system_wide                     =  0;
  54
  55 static int                      default_interval                = 100000;
  56
  57 static u64                      count_filter                    =  5;
  58 static int                      print_entries                   = 15;
  59
  60 static int                      target_pid                      = -1;
  61 static int                      profile_cpu                     = -1;
  62 static int                      nr_cpus                         =  0;
  63 static unsigned int             realtime_prio                   =  0;
  64 static int                      group                           =  0;
  65 static unsigned int             page_size;
  66 static unsigned int             mmap_pages                      = 16;
  67 static int                      freq                            =  0;
  68 static int                      verbose                         =  0;
  69 static char                     *vmlinux                        =  NULL;
  70
  71 static char                     *sym_filter;
  72 static unsigned long            filter_start;
  73 static unsigned long            filter_end;
  74
  75 static int                      delay_secs                      =  2;
  76 static int                      zero;
  77 static int                      dump_symtab;
  78
  79 /*
  80  * Symbols
  81  */
  82
  83 static u64                      min_ip;
  84 static u64                      max_ip = -1ll;
  85
  86 struct sym_entry {
  87         struct rb_node          rb_node;
  88         struct list_head        node;
  89         unsigned long           count[MAX_COUNTERS];
  90         unsigned long           snap_count;
  91         double                  weight;
  92         int                     skip;
  93 };
  94
  95 struct sym_entry                *sym_filter_entry;
  96
  97 struct dso                      *kernel_dso;
  98
  99 /*
 100  * Symbols will be added here in record_ip and will get out
 101  * after decayed.
 102  */
 103 static LIST_HEAD(active_symbols);
 104 static pthread_mutex_t active_symbols_lock = PTHREAD_MUTEX_INITIALIZER;
 105
 106 /*
 107  * Ordering weight: count-1 * count-2 * ... / count-n
 108  */
 109 static double sym_weight(const struct sym_entry *sym)
 110 {
 111         double weight = sym->snap_count;
 112         int counter;
 113
 114         for (counter = 1; counter < nr_counters-1; counter++)
 115                 weight *= sym->count[counter];
 116
 117         weight /= (sym->count[counter] + 1);
 118
 119         return weight;
 120 }
 121
 122 static long                     samples;
 123 static long                     userspace_samples;
 124 static const char               CONSOLE_CLEAR[] = "\e[H\e[2J";
 125
 126 static void __list_insert_active_sym(struct sym_entry *syme)
 127 {
 128         list_add(&syme->node, &active_symbols);
 129 }
 130
 131 static void list_remove_active_sym(struct sym_entry *syme)
 132 {
 133         pthread_mutex_lock(&active_symbols_lock);
 134         list_del_init(&syme->node);
 135         pthread_mutex_unlock(&active_symbols_lock);
 136 }
 137
 138 static void rb_insert_active_sym(struct rb_root *tree, struct sym_entry *se)
 139 {
 140         struct rb_node **p = &tree->rb_node;
 141         struct rb_node *parent = NULL;
 142         struct sym_entry *iter;
 143
 144         while (*p != NULL) {
 145                 parent = *p;
 146                 iter = rb_entry(parent, struct sym_entry, rb_node);
 147
 148                 if (se->weight > iter->weight)
 149                         p = &(*p)->rb_left;
 150                 else
 151                         p = &(*p)->rb_right;
 152         }
 153
 154         rb_link_node(&se->rb_node, parent, p);
 155         rb_insert_color(&se->rb_node, tree);
 156 }
 157
 158 static void print_sym_table(void)
 159 {
 160         int printed = 0, j;
 161         int counter;
 162         float samples_per_sec = samples/delay_secs;
 163         float ksamples_per_sec = (samples-userspace_samples)/delay_secs;
 164         float sum_ksamples = 0.0;
 165         struct sym_entry *syme, *n;
 166         struct rb_root tmp = RB_ROOT;
 167         struct rb_node *nd;
 168
 169         samples = userspace_samples = 0;
 170
 171         /* Sort the active symbols */
 172         pthread_mutex_lock(&active_symbols_lock);
 173         syme = list_entry(active_symbols.next, struct sym_entry, node);
 174         pthread_mutex_unlock(&active_symbols_lock);
 175
 176         list_for_each_entry_safe_from(syme, n, &active_symbols, node) {
 177                 syme->snap_count = syme->count[0];
 178                 if (syme->snap_count != 0) {
 179                         syme->weight = sym_weight(syme);
 180                         rb_insert_active_sym(&tmp, syme);
 181                         sum_ksamples += syme->snap_count;
 182
 183                         for (j = 0; j < nr_counters; j++)
 184                                 syme->count[j] = zero ? 0 : syme->count[j] * 7 / 8;
 185                 } else
 186                         list_remove_active_sym(syme);
 187         }
 188
 189         puts(CONSOLE_CLEAR);
 190
 191         printf(
 192 "------------------------------------------------------------------------------\n");
 193         printf( "   PerfTop:%8.0f irqs/sec  kernel:%4.1f%% [",
 194                 samples_per_sec,
 195                 100.0 - (100.0*((samples_per_sec-ksamples_per_sec)/samples_per_sec)));
 196
 197         if (nr_counters == 1) {
 198                 printf("%Ld", (u64)attrs[0].sample_period);
 199                 if (freq)
 200                         printf("Hz ");
 201                 else
 202                         printf(" ");
 203         }
 204
 205         for (counter = 0; counter < nr_counters; counter++) {
 206                 if (counter)
 207                         printf("/");
 208
 209                 printf("%s", event_name(counter));
 210         }
 211
 212         printf( "], ");
 213
 214         if (target_pid != -1)
 215                 printf(" (target_pid: %d", target_pid);
 216         else
 217                 printf(" (all");
 218
 219         if (profile_cpu != -1)
 220                 printf(", cpu: %d)\n", profile_cpu);
 221         else {
 222                 if (target_pid != -1)
 223                         printf(")\n");
 224                 else
 225                         printf(", %d CPUs)\n", nr_cpus);
 226         }
 227
 228         printf("------------------------------------------------------------------------------\n\n");
 229
 230         if (nr_counters == 1)
 231                 printf("             samples    pcnt");
 232         else
 233                 printf("  weight     samples    pcnt");
 234
 235         printf("         RIP          kernel function\n"
 236                        "  ______     _______   _____   ________________   _______________\n\n"
 237         );
 238
 239         for (nd = rb_first(&tmp); nd; nd = rb_next(nd)) {
 240                 struct sym_entry *syme = rb_entry(nd, struct sym_entry, rb_node);
 241                 struct symbol *sym = (struct symbol *)(syme + 1);
 242                 double pcnt;
 243
 244                 if (++printed > print_entries || syme->snap_count < count_filter)
 245                         continue;
 246
 247                 pcnt = 100.0 - (100.0 * ((sum_ksamples - syme->snap_count) /
 248                                          sum_ksamples));
 249
 250                 if (nr_counters == 1)
 251                         printf("%20.2f - ", syme->weight);
 252                 else
 253                         printf("%9.1f %10ld - ", syme->weight, syme->snap_count);
 254
 255                 percent_color_fprintf(stdout, "%4.1f%%", pcnt);
 256                 printf(" - %016llx : %s", sym->start, sym->name);
 257                 if (sym->module)
 258                         printf("\t[%s]", sym->module->name);
 259                 printf("\n");
 260         }
 261 }
 262
 263 static void *display_thread(void *arg __used)
 264 {
 265         struct pollfd stdin_poll = { .fd = 0, .events = POLLIN };
 266         int delay_msecs = delay_secs * 1000;
 267
 268         printf("PerfTop refresh period: %d seconds\n", delay_secs);
 269
 270         do {
 271                 print_sym_table();
 272         } while (!poll(&stdin_poll, 1, delay_msecs) == 1);
 273
 274         printf("key pressed - exiting.\n");
 275         exit(0);
 276
 277         return NULL;
 278 }
 279
 280 /* Tag samples to be skipped. */
 281 static const char *skip_symbols[] = {
 282         "default_idle",
 283         "cpu_idle",
 284         "enter_idle",
 285         "exit_idle",
 286         "mwait_idle",
 287         "ppc64_runlatch_off",
 288         "pseries_dedicated_idle_sleep",
 289         NULL
 290 };
 291
 292 static int symbol_filter(struct dso *self, struct symbol *sym)
 293 {
 294         static int filter_match;
 295         struct sym_entry *syme;
 296         const char *name = sym->name;
 297         int i;
 298
 299         /*
 300          * ppc64 uses function descriptors and appends a '.' to the
 301          * start of every instruction address. Remove it.
 302          */
 303         if (name[0] == '.')
 304                 name++;
 305
 306         if (!strcmp(name, "_text") ||
 307             !strcmp(name, "_etext") ||
 308             !strcmp(name, "_sinittext") ||
 309             !strncmp("init_module", name, 11) ||
 310             !strncmp("cleanup_module", name, 14) ||
 311             strstr(name, "_text_start") ||
 312             strstr(name, "_text_end"))
 313                 return 1;
 314
 315         syme = dso__sym_priv(self, sym);
 316         for (i = 0; skip_symbols[i]; i++) {
 317                 if (!strcmp(skip_symbols[i], name)) {
 318                         syme->skip = 1;
 319                         break;
 320                 }
 321         }
 322
 323         if (filter_match == 1) {
 324                 filter_end = sym->start;
 325                 filter_match = -1;
 326                 if (filter_end - filter_start > 10000) {
 327                         fprintf(stderr,
 328                                 "hm, too large filter symbol <%s> - skipping.\n",
 329                                 sym_filter);
 330                         fprintf(stderr, "symbol filter start: %016lx\n",
 331                                 filter_start);
 332                         fprintf(stderr, "                end: %016lx\n",
 333                                 filter_end);
 334                         filter_end = filter_start = 0;
 335                         sym_filter = NULL;
 336                         sleep(1);
 337                 }
 338         }
 339
 340         if (filter_match == 0 && sym_filter && !strcmp(name, sym_filter)) {
 341                 filter_match = 1;
 342                 filter_start = sym->start;
 343         }
 344
 345
 346         return 0;
 347 }
 348
 349 static int parse_symbols(void)
 350 {
 351         struct rb_node *node;
 352         struct symbol  *sym;
 353         int modules = vmlinux ? 1 : 0;
 354
 355         kernel_dso = dso__new("[kernel]", sizeof(struct sym_entry));
 356         if (kernel_dso == NULL)
 357                 return -1;
 358
 359         if (dso__load_kernel(kernel_dso, vmlinux, symbol_filter, verbose, modules) <= 0)
 360                 goto out_delete_dso;
 361
 362         node = rb_first(&kernel_dso->syms);
 363         sym = rb_entry(node, struct symbol, rb_node);
 364         min_ip = sym->start;
 365
 366         node = rb_last(&kernel_dso->syms);
 367         sym = rb_entry(node, struct symbol, rb_node);
 368         max_ip = sym->end;
 369
 370         if (dump_symtab)
 371                 dso__fprintf(kernel_dso, stderr);
 372
 373         return 0;
 374
 375 out_delete_dso:
 376         dso__delete(kernel_dso);
 377         kernel_dso = NULL;
 378         return -1;
 379 }
 380
 381 #define TRACE_COUNT     3
 382
 383 /*
 384  * Binary search in the histogram table and record the hit:
 385  */
 386 static void record_ip(u64 ip, int counter)
 387 {
 388         struct symbol *sym = dso__find_symbol(kernel_dso, ip);
 389
 390         if (sym != NULL) {
 391                 struct sym_entry *syme = dso__sym_priv(kernel_dso, sym);
 392
 393                 if (!syme->skip) {
 394                         syme->count[counter]++;
 395                         pthread_mutex_lock(&active_symbols_lock);
 396                         if (list_empty(&syme->node) || !syme->node.next)
 397                                 __list_insert_active_sym(syme);
 398                         pthread_mutex_unlock(&active_symbols_lock);
 399                         return;
 400                 }
 401         }
 402
 403         samples--;
 404 }
 405
 406 static void process_event(u64 ip, int counter, int user)
 407 {
 408         samples++;
 409
 410         if (user) {
 411                 userspace_samples++;
 412                 return;
 413         }
 414
 415         record_ip(ip, counter);
 416 }
 417
 418 struct mmap_data {
 419         int                     counter;
 420         void                    *base;
 421         int                     mask;
 422         unsigned int            prev;
 423 };
 424
 425 static unsigned int mmap_read_head(struct mmap_data *md)
 426 {
 427         struct perf_counter_mmap_page *pc = md->base;
 428         int head;
 429
 430         head = pc->data_head;
 431         rmb();
 432
 433         return head;
 434 }
 435
 436 struct timeval last_read, this_read;
 437
 438 static void mmap_read_counter(struct mmap_data *md)
 439 {
 440         unsigned int head = mmap_read_head(md);
 441         unsigned int old = md->prev;
 442         unsigned char *data = md->base + page_size;
 443         int diff;
 444
 445         gettimeofday(&this_read, NULL);
 446
 447         /*
 448          * If we're further behind than half the buffer, there's a chance
 449          * the writer will bite our tail and mess up the samples under us.
 450          *
 451          * If we somehow ended up ahead of the head, we got messed up.
 452          *
 453          * In either case, truncate and restart at head.
 454          */
 455         diff = head - old;
 456         if (diff > md->mask / 2 || diff < 0) {
 457                 struct timeval iv;
 458                 unsigned long msecs;
 459
 460                 timersub(&this_read, &last_read, &iv);
 461                 msecs = iv.tv_sec*1000 + iv.tv_usec/1000;
 462
 463                 fprintf(stderr, "WARNING: failed to keep up with mmap data."
 464                                 "  Last read %lu msecs ago.\n", msecs);
 465
 466                 /*
 467                  * head points to a known good entry, start there.
 468                  */
 469                 old = head;
 470         }
 471
 472         last_read = this_read;
 473
 474         for (; old != head;) {
 475                 struct ip_event {
 476                         struct perf_event_header header;
 477                         u64 ip;
 478                         u32 pid, target_pid;
 479                 };
 480                 struct mmap_event {
 481                         struct perf_event_header header;
 482                         u32 pid, target_pid;
 483                         u64 start;
 484                         u64 len;
 485                         u64 pgoff;
 486                         char filename[PATH_MAX];
 487                 };
 488
 489                 typedef union event_union {
 490                         struct perf_event_header header;
 491                         struct ip_event ip;
 492                         struct mmap_event mmap;
 493                 } event_t;
 494
 495                 event_t *event = (event_t *)&data[old & md->mask];
 496
 497                 event_t event_copy;
 498
 499                 size_t size = event->header.size;
 500
 501                 /*
 502                  * Event straddles the mmap boundary -- header should always
 503                  * be inside due to u64 alignment of output.
 504                  */
 505                 if ((old & md->mask) + size != ((old + size) & md->mask)) {
 506                         unsigned int offset = old;
 507                         unsigned int len = min(sizeof(*event), size), cpy;
 508                         void *dst = &event_copy;
 509
 510                         do {
 511                                 cpy = min(md->mask + 1 - (offset & md->mask), len);
 512                                 memcpy(dst, &data[offset & md->mask], cpy);
 513                                 offset += cpy;
 514                                 dst += cpy;
 515                                 len -= cpy;
 516                         } while (len);
 517
 518                         event = &event_copy;
 519                 }
 520
 521                 old += size;
 522
 523                 if (event->header.type == PERF_EVENT_SAMPLE) {
 524                         int user =
 525         (event->header.misc & PERF_EVENT_MISC_CPUMODE_MASK) == PERF_EVENT_MISC_USER;
 526                         process_event(event->ip.ip, md->counter, user);
 527                 }
 528         }
 529
 530         md->prev = old;
 531 }
 532
 533 static struct pollfd event_array[MAX_NR_CPUS * MAX_COUNTERS];
 534 static struct mmap_data mmap_array[MAX_NR_CPUS][MAX_COUNTERS];
 535
 536 static void mmap_read(void)
 537 {
 538         int i, counter;
 539
 540         for (i = 0; i < nr_cpus; i++) {
 541                 for (counter = 0; counter < nr_counters; counter++)
 542                         mmap_read_counter(&mmap_array[i][counter]);
 543         }
 544 }
 545
 546 int nr_poll;
 547 int group_fd;
 548
 549 static void start_counter(int i, int counter)
 550 {
 551         struct perf_counter_attr *attr;
 552         unsigned int cpu;
 553
 554         cpu = profile_cpu;
 555         if (target_pid == -1 && profile_cpu == -1)
 556                 cpu = i;
 557
 558         attr = attrs + counter;
 559
 560         attr->sample_type       = PERF_SAMPLE_IP | PERF_SAMPLE_TID;
 561         attr->freq              = freq;
 562
 563 try_again:
 564         fd[i][counter] = sys_perf_counter_open(attr, target_pid, cpu, group_fd, 0);
 565
 566         if (fd[i][counter] < 0) {
 567                 int err = errno;
 568
 569                 if (err == EPERM)
 570                         die("No permission - are you root?\n");
 571                 /*
 572                  * If it's cycles then fall back to hrtimer
 573                  * based cpu-clock-tick sw counter, which
 574                  * is always available even if no PMU support:
 575                  */
 576                 if (attr->type == PERF_TYPE_HARDWARE
 577                         && attr->config == PERF_COUNT_HW_CPU_CYCLES) {
 578
 579                         if (verbose)
 580                                 warning(" ... trying to fall back to cpu-clock-ticks\n");
 581
 582                         attr->type = PERF_TYPE_SOFTWARE;
 583                         attr->config = PERF_COUNT_SW_CPU_CLOCK;
 584                         goto try_again;
 585                 }
 586                 printf("\n");
 587                 error("perfcounter syscall returned with %d (%s)\n",
 588                         fd[i][counter], strerror(err));
 589                 die("No CONFIG_PERF_COUNTERS=y kernel support configured?\n");
 590                 exit(-1);
 591         }
 592         assert(fd[i][counter] >= 0);
 593         fcntl(fd[i][counter], F_SETFL, O_NONBLOCK);
 594
 595         /*
 596          * First counter acts as the group leader:
 597          */
 598         if (group && group_fd == -1)
 599                 group_fd = fd[i][counter];
 600
 601         event_array[nr_poll].fd = fd[i][counter];
 602         event_array[nr_poll].events = POLLIN;
 603         nr_poll++;
 604
 605         mmap_array[i][counter].counter = counter;
 606         mmap_array[i][counter].prev = 0;
 607         mmap_array[i][counter].mask = mmap_pages*page_size - 1;
 608         mmap_array[i][counter].base = mmap(NULL, (mmap_pages+1)*page_size,
 609                         PROT_READ, MAP_SHARED, fd[i][counter], 0);
 610         if (mmap_array[i][counter].base == MAP_FAILED)
 611                 die("failed to mmap with %d (%s)\n", errno, strerror(errno));
 612 }
 613
 614 static int __cmd_top(void)
 615 {
 616         pthread_t thread;
 617         int i, counter;
 618         int ret;
 619
 620         for (i = 0; i < nr_cpus; i++) {
 621                 group_fd = -1;
 622                 for (counter = 0; counter < nr_counters; counter++)
 623                         start_counter(i, counter);
 624         }
 625
 626         /* Wait for a minimal set of events before starting the snapshot */
 627         poll(event_array, nr_poll, 100);
 628
 629         mmap_read();
 630
 631         if (pthread_create(&thread, NULL, display_thread, NULL)) {
 632                 printf("Could not create display thread.\n");
 633                 exit(-1);
 634         }
 635
 636         if (realtime_prio) {
 637                 struct sched_param param;
 638
 639                 param.sched_priority = realtime_prio;
 640                 if (sched_setscheduler(0, SCHED_FIFO, &param)) {
 641                         printf("Could not set realtime priority.\n");
 642                         exit(-1);
 643                 }
 644         }
 645
 646         while (1) {
 647                 int hits = samples;
 648
 649                 mmap_read();
 650
 651                 if (hits == samples)
 652                         ret = poll(event_array, nr_poll, 100);
 653         }
 654
 655         return 0;
 656 }
 657
 658 static const char * const top_usage[] = {
 659         "perf top [<options>]",
 660         NULL
 661 };
 662
 663 static const struct option options[] = {
 664         OPT_CALLBACK('e', "event", NULL, "event",
 665                      "event selector. use 'perf list' to list available events",
 666                      parse_events),
 667         OPT_INTEGER('c', "count", &default_interval,
 668                     "event period to sample"),
 669         OPT_INTEGER('p', "pid", &target_pid,
 670                     "profile events on existing pid"),
 671         OPT_BOOLEAN('a', "all-cpus", &system_wide,
 672                             "system-wide collection from all CPUs"),
 673         OPT_INTEGER('C', "CPU", &profile_cpu,
 674                     "CPU to profile on"),
 675         OPT_STRING('k', "vmlinux", &vmlinux, "file", "vmlinux pathname"),
 676         OPT_INTEGER('m', "mmap-pages", &mmap_pages,
 677                     "number of mmap data pages"),
 678         OPT_INTEGER('r', "realtime", &realtime_prio,
 679                     "collect data with this RT SCHED_FIFO priority"),
 680         OPT_INTEGER('d', "delay", &delay_secs,
 681                     "number of seconds to delay between refreshes"),
 682         OPT_BOOLEAN('D', "dump-symtab", &dump_symtab,
 683                             "dump the symbol table used for profiling"),
 684         OPT_INTEGER('f', "count-filter", &count_filter,
 685                     "only display functions with more events than this"),
 686         OPT_BOOLEAN('g', "group", &group,
 687                             "put the counters into a counter group"),
 688         OPT_STRING('s', "sym-filter", &sym_filter, "pattern",
 689                     "only display symbols matchig this pattern"),
 690         OPT_BOOLEAN('z', "zero", &zero,
 691                     "zero history across updates"),
 692         OPT_INTEGER('F', "freq", &freq,
 693                     "profile at this frequency"),
 694         OPT_INTEGER('E', "entries", &print_entries,
 695                     "display this many functions"),
 696         OPT_BOOLEAN('v', "verbose", &verbose,
 697                     "be more verbose (show counter open errors, etc)"),
 698         OPT_END()
 699 };
 700
 701 int cmd_top(int argc, const char **argv, const char *prefix __used)
 702 {
 703         int counter;
 704
 705         symbol__init();
 706
 707         page_size = sysconf(_SC_PAGE_SIZE);
 708
 709         argc = parse_options(argc, argv, options, top_usage, 0);
 710         if (argc)
 711                 usage_with_options(top_usage, options);
 712
 713         if (freq) {
 714                 default_interval = freq;
 715                 freq = 1;
 716         }
 717
 718         /* CPU and PID are mutually exclusive */
 719         if (target_pid != -1 && profile_cpu != -1) {
 720                 printf("WARNING: PID switch overriding CPU\n");
 721                 sleep(1);
 722                 profile_cpu = -1;
 723         }
 724
 725         if (!nr_counters)
 726                 nr_counters = 1;
 727
 728         if (delay_secs < 1)
 729                 delay_secs = 1;
 730
 731         parse_symbols();
 732
 733         /*
 734          * Fill in the ones not specifically initialized via -c:
 735          */
 736         for (counter = 0; counter < nr_counters; counter++) {
 737                 if (attrs[counter].sample_period)
 738                         continue;
 739
 740                 attrs[counter].sample_period = default_interval;
 741         }
 742
 743         nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
 744         assert(nr_cpus <= MAX_NR_CPUS);
 745         assert(nr_cpus >= 0);
 746
 747         if (target_pid != -1 || profile_cpu != -1)
 748                 nr_cpus = 1;
 749
 750         return __cmd_top();
 751 }