1 // SPDX-License-Identifier: GPL-2.0 2 3 /* Copyright (c) 2019 Facebook */ 4 5 #include <assert.h> 6 #include <limits.h> 7 #include <unistd.h> 8 #include <sys/file.h> 9 #include <sys/time.h> 10 #include <linux/err.h> 11 #include <linux/zalloc.h> 12 #include <api/fs/fs.h> 13 #include <perf/bpf_perf.h> 14 15 #include "bpf_counter.h" 16 #include "bpf-utils.h" 17 #include "counts.h" 18 #include "debug.h" 19 #include "evsel.h" 20 #include "evlist.h" 21 #include "target.h" 22 #include "cgroup.h" 23 #include "cpumap.h" 24 #include "thread_map.h" 25 26 #include "bpf_skel/bpf_prog_profiler.skel.h" 27 #include "bpf_skel/bperf_u.h" 28 #include "bpf_skel/bperf_leader.skel.h" 29 #include "bpf_skel/bperf_follower.skel.h" 30 31 #define ATTR_MAP_SIZE 16 32 33 static inline void *u64_to_ptr(__u64 ptr) 34 { 35 return (void *)(unsigned long)ptr; 36 } 37 38 static struct bpf_counter *bpf_counter_alloc(void) 39 { 40 struct bpf_counter *counter; 41 42 counter = zalloc(sizeof(*counter)); 43 if (counter) 44 INIT_LIST_HEAD(&counter->list); 45 return counter; 46 } 47 48 static int bpf_program_profiler__destroy(struct evsel *evsel) 49 { 50 struct bpf_counter *counter, *tmp; 51 52 list_for_each_entry_safe(counter, tmp, 53 &evsel->bpf_counter_list, list) { 54 list_del_init(&counter->list); 55 bpf_prog_profiler_bpf__destroy(counter->skel); 56 free(counter); 57 } 58 assert(list_empty(&evsel->bpf_counter_list)); 59 60 return 0; 61 } 62 63 static char *bpf_target_prog_name(int tgt_fd) 64 { 65 struct bpf_func_info *func_info; 66 struct perf_bpil *info_linear; 67 const struct btf_type *t; 68 struct btf *btf = NULL; 69 char *name = NULL; 70 71 info_linear = get_bpf_prog_info_linear(tgt_fd, 1UL << PERF_BPIL_FUNC_INFO); 72 if (IS_ERR_OR_NULL(info_linear)) { 73 pr_debug("failed to get info_linear for prog FD %d\n", tgt_fd); 74 return NULL; 75 } 76 77 if (info_linear->info.btf_id == 0) { 78 pr_debug("prog FD %d doesn't have valid btf\n", tgt_fd); 79 goto out; 80 } 81 82 btf = btf__load_from_kernel_by_id(info_linear->info.btf_id); 83 if (libbpf_get_error(btf)) { 84 pr_debug("failed to load btf for prog FD %d\n", tgt_fd); 85 goto out; 86 } 87 88 func_info = u64_to_ptr(info_linear->info.func_info); 89 t = btf__type_by_id(btf, func_info[0].type_id); 90 if (!t) { 91 pr_debug("btf %d doesn't have type %d\n", 92 info_linear->info.btf_id, func_info[0].type_id); 93 goto out; 94 } 95 name = strdup(btf__name_by_offset(btf, t->name_off)); 96 out: 97 btf__free(btf); 98 free(info_linear); 99 return name; 100 } 101 102 static int bpf_program_profiler_load_one(struct evsel *evsel, u32 prog_id) 103 { 104 struct bpf_prog_profiler_bpf *skel; 105 struct bpf_counter *counter; 106 struct bpf_program *prog; 107 char *prog_name; 108 int prog_fd; 109 int err; 110 111 prog_fd = bpf_prog_get_fd_by_id(prog_id); 112 if (prog_fd < 0) { 113 pr_err("Failed to open fd for bpf prog %u\n", prog_id); 114 return -1; 115 } 116 counter = bpf_counter_alloc(); 117 if (!counter) { 118 close(prog_fd); 119 return -1; 120 } 121 122 skel = bpf_prog_profiler_bpf__open(); 123 if (!skel) { 124 pr_err("Failed to open bpf skeleton\n"); 125 goto err_out; 126 } 127 128 skel->rodata->num_cpu = evsel__nr_cpus(evsel); 129 130 bpf_map__set_max_entries(skel->maps.events, evsel__nr_cpus(evsel)); 131 bpf_map__set_max_entries(skel->maps.fentry_readings, 1); 132 bpf_map__set_max_entries(skel->maps.accum_readings, 1); 133 134 prog_name = bpf_target_prog_name(prog_fd); 135 if (!prog_name) { 136 pr_err("Failed to get program name for bpf prog %u. Does it have BTF?\n", prog_id); 137 goto err_out; 138 } 139 140 bpf_object__for_each_program(prog, skel->obj) { 141 err = bpf_program__set_attach_target(prog, prog_fd, prog_name); 142 if (err) { 143 pr_err("bpf_program__set_attach_target failed.\n" 144 "Does bpf prog %u have BTF?\n", prog_id); 145 goto err_out; 146 } 147 } 148 set_max_rlimit(); 149 err = bpf_prog_profiler_bpf__load(skel); 150 if (err) { 151 pr_err("bpf_prog_profiler_bpf__load failed\n"); 152 goto err_out; 153 } 154 155 assert(skel != NULL); 156 counter->skel = skel; 157 list_add(&counter->list, &evsel->bpf_counter_list); 158 close(prog_fd); 159 return 0; 160 err_out: 161 bpf_prog_profiler_bpf__destroy(skel); 162 free(counter); 163 close(prog_fd); 164 return -1; 165 } 166 167 static int bpf_program_profiler__load(struct evsel *evsel, struct target *target) 168 { 169 char *bpf_str, *bpf_str_, *tok, *saveptr = NULL, *p; 170 u32 prog_id; 171 int ret; 172 173 bpf_str_ = bpf_str = strdup(target->bpf_str); 174 if (!bpf_str) 175 return -1; 176 177 while ((tok = strtok_r(bpf_str, ",", &saveptr)) != NULL) { 178 prog_id = strtoul(tok, &p, 10); 179 if (prog_id == 0 || prog_id == UINT_MAX || 180 (*p != '\0' && *p != ',')) { 181 pr_err("Failed to parse bpf prog ids %s\n", 182 target->bpf_str); 183 return -1; 184 } 185 186 ret = bpf_program_profiler_load_one(evsel, prog_id); 187 if (ret) { 188 bpf_program_profiler__destroy(evsel); 189 free(bpf_str_); 190 return -1; 191 } 192 bpf_str = NULL; 193 } 194 free(bpf_str_); 195 return 0; 196 } 197 198 static int bpf_program_profiler__enable(struct evsel *evsel) 199 { 200 struct bpf_counter *counter; 201 int ret; 202 203 list_for_each_entry(counter, &evsel->bpf_counter_list, list) { 204 assert(counter->skel != NULL); 205 ret = bpf_prog_profiler_bpf__attach(counter->skel); 206 if (ret) { 207 bpf_program_profiler__destroy(evsel); 208 return ret; 209 } 210 } 211 return 0; 212 } 213 214 static int bpf_program_profiler__disable(struct evsel *evsel) 215 { 216 struct bpf_counter *counter; 217 218 list_for_each_entry(counter, &evsel->bpf_counter_list, list) { 219 assert(counter->skel != NULL); 220 bpf_prog_profiler_bpf__detach(counter->skel); 221 } 222 return 0; 223 } 224 225 static int bpf_program_profiler__read(struct evsel *evsel) 226 { 227 // BPF_MAP_TYPE_PERCPU_ARRAY uses /sys/devices/system/cpu/possible 228 // Sometimes possible > online, like on a Ryzen 3900X that has 24 229 // threads but its possible showed 0-31 -acme 230 int num_cpu_bpf = libbpf_num_possible_cpus(); 231 struct bpf_perf_event_value values[num_cpu_bpf]; 232 struct bpf_counter *counter; 233 struct perf_counts_values *counts; 234 int reading_map_fd; 235 __u32 key = 0; 236 int err, idx, bpf_cpu; 237 238 if (list_empty(&evsel->bpf_counter_list)) 239 return -EAGAIN; 240 241 perf_cpu_map__for_each_idx(idx, evsel__cpus(evsel)) { 242 counts = perf_counts(evsel->counts, idx, 0); 243 counts->val = 0; 244 counts->ena = 0; 245 counts->run = 0; 246 } 247 list_for_each_entry(counter, &evsel->bpf_counter_list, list) { 248 struct bpf_prog_profiler_bpf *skel = counter->skel; 249 250 assert(skel != NULL); 251 reading_map_fd = bpf_map__fd(skel->maps.accum_readings); 252 253 err = bpf_map_lookup_elem(reading_map_fd, &key, values); 254 if (err) { 255 pr_err("failed to read value\n"); 256 return err; 257 } 258 259 for (bpf_cpu = 0; bpf_cpu < num_cpu_bpf; bpf_cpu++) { 260 idx = perf_cpu_map__idx(evsel__cpus(evsel), 261 (struct perf_cpu){.cpu = bpf_cpu}); 262 if (idx == -1) 263 continue; 264 counts = perf_counts(evsel->counts, idx, 0); 265 counts->val += values[bpf_cpu].counter; 266 counts->ena += values[bpf_cpu].enabled; 267 counts->run += values[bpf_cpu].running; 268 } 269 } 270 return 0; 271 } 272 273 static int bpf_program_profiler__install_pe(struct evsel *evsel, int cpu_map_idx, 274 int fd) 275 { 276 struct bpf_prog_profiler_bpf *skel; 277 struct bpf_counter *counter; 278 int ret; 279 280 list_for_each_entry(counter, &evsel->bpf_counter_list, list) { 281 skel = counter->skel; 282 assert(skel != NULL); 283 284 ret = bpf_map_update_elem(bpf_map__fd(skel->maps.events), 285 &cpu_map_idx, &fd, BPF_ANY); 286 if (ret) 287 return ret; 288 } 289 return 0; 290 } 291 292 struct bpf_counter_ops bpf_program_profiler_ops = { 293 .load = bpf_program_profiler__load, 294 .enable = bpf_program_profiler__enable, 295 .disable = bpf_program_profiler__disable, 296 .read = bpf_program_profiler__read, 297 .destroy = bpf_program_profiler__destroy, 298 .install_pe = bpf_program_profiler__install_pe, 299 }; 300 301 static bool bperf_attr_map_compatible(int attr_map_fd) 302 { 303 struct bpf_map_info map_info = {0}; 304 __u32 map_info_len = sizeof(map_info); 305 int err; 306 307 err = bpf_obj_get_info_by_fd(attr_map_fd, &map_info, &map_info_len); 308 309 if (err) 310 return false; 311 return (map_info.key_size == sizeof(struct perf_event_attr)) && 312 (map_info.value_size == sizeof(struct perf_event_attr_map_entry)); 313 } 314 315 static int bperf_lock_attr_map(struct target *target) 316 { 317 char path[PATH_MAX]; 318 int map_fd, err; 319 320 if (target->attr_map) { 321 scnprintf(path, PATH_MAX, "%s", target->attr_map); 322 } else { 323 scnprintf(path, PATH_MAX, "%s/fs/bpf/%s", sysfs__mountpoint(), 324 BPF_PERF_DEFAULT_ATTR_MAP_PATH); 325 } 326 327 if (access(path, F_OK)) { 328 map_fd = bpf_map_create(BPF_MAP_TYPE_HASH, NULL, 329 sizeof(struct perf_event_attr), 330 sizeof(struct perf_event_attr_map_entry), 331 ATTR_MAP_SIZE, NULL); 332 if (map_fd < 0) 333 return -1; 334 335 err = bpf_obj_pin(map_fd, path); 336 if (err) { 337 /* someone pinned the map in parallel? */ 338 close(map_fd); 339 map_fd = bpf_obj_get(path); 340 if (map_fd < 0) 341 return -1; 342 } 343 } else { 344 map_fd = bpf_obj_get(path); 345 if (map_fd < 0) 346 return -1; 347 } 348 349 if (!bperf_attr_map_compatible(map_fd)) { 350 close(map_fd); 351 return -1; 352 353 } 354 err = flock(map_fd, LOCK_EX); 355 if (err) { 356 close(map_fd); 357 return -1; 358 } 359 return map_fd; 360 } 361 362 static int bperf_check_target(struct evsel *evsel, 363 struct target *target, 364 enum bperf_filter_type *filter_type, 365 __u32 *filter_entry_cnt) 366 { 367 if (evsel->core.leader->nr_members > 1) { 368 pr_err("bpf managed perf events do not yet support groups.\n"); 369 return -1; 370 } 371 372 /* determine filter type based on target */ 373 if (target->system_wide) { 374 *filter_type = BPERF_FILTER_GLOBAL; 375 *filter_entry_cnt = 1; 376 } else if (target->cpu_list) { 377 *filter_type = BPERF_FILTER_CPU; 378 *filter_entry_cnt = perf_cpu_map__nr(evsel__cpus(evsel)); 379 } else if (target->tid) { 380 *filter_type = BPERF_FILTER_PID; 381 *filter_entry_cnt = perf_thread_map__nr(evsel->core.threads); 382 } else if (target->pid || evsel->evlist->workload.pid != -1) { 383 *filter_type = BPERF_FILTER_TGID; 384 *filter_entry_cnt = perf_thread_map__nr(evsel->core.threads); 385 } else { 386 pr_err("bpf managed perf events do not yet support these targets.\n"); 387 return -1; 388 } 389 390 return 0; 391 } 392 393 static struct perf_cpu_map *all_cpu_map; 394 395 static int bperf_reload_leader_program(struct evsel *evsel, int attr_map_fd, 396 struct perf_event_attr_map_entry *entry) 397 { 398 struct bperf_leader_bpf *skel = bperf_leader_bpf__open(); 399 int link_fd, diff_map_fd, err; 400 struct bpf_link *link = NULL; 401 402 if (!skel) { 403 pr_err("Failed to open leader skeleton\n"); 404 return -1; 405 } 406 407 bpf_map__set_max_entries(skel->maps.events, libbpf_num_possible_cpus()); 408 err = bperf_leader_bpf__load(skel); 409 if (err) { 410 pr_err("Failed to load leader skeleton\n"); 411 goto out; 412 } 413 414 link = bpf_program__attach(skel->progs.on_switch); 415 if (IS_ERR(link)) { 416 pr_err("Failed to attach leader program\n"); 417 err = PTR_ERR(link); 418 goto out; 419 } 420 421 link_fd = bpf_link__fd(link); 422 diff_map_fd = bpf_map__fd(skel->maps.diff_readings); 423 entry->link_id = bpf_link_get_id(link_fd); 424 entry->diff_map_id = bpf_map_get_id(diff_map_fd); 425 err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, entry, BPF_ANY); 426 assert(err == 0); 427 428 evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry->link_id); 429 assert(evsel->bperf_leader_link_fd >= 0); 430 431 /* 432 * save leader_skel for install_pe, which is called within 433 * following evsel__open_per_cpu call 434 */ 435 evsel->leader_skel = skel; 436 evsel__open_per_cpu(evsel, all_cpu_map, -1); 437 438 out: 439 bperf_leader_bpf__destroy(skel); 440 bpf_link__destroy(link); 441 return err; 442 } 443 444 static int bperf__load(struct evsel *evsel, struct target *target) 445 { 446 struct perf_event_attr_map_entry entry = {0xffffffff, 0xffffffff}; 447 int attr_map_fd, diff_map_fd = -1, err; 448 enum bperf_filter_type filter_type; 449 __u32 filter_entry_cnt, i; 450 451 if (bperf_check_target(evsel, target, &filter_type, &filter_entry_cnt)) 452 return -1; 453 454 if (!all_cpu_map) { 455 all_cpu_map = perf_cpu_map__new(NULL); 456 if (!all_cpu_map) 457 return -1; 458 } 459 460 evsel->bperf_leader_prog_fd = -1; 461 evsel->bperf_leader_link_fd = -1; 462 463 /* 464 * Step 1: hold a fd on the leader program and the bpf_link, if 465 * the program is not already gone, reload the program. 466 * Use flock() to ensure exclusive access to the perf_event_attr 467 * map. 468 */ 469 attr_map_fd = bperf_lock_attr_map(target); 470 if (attr_map_fd < 0) { 471 pr_err("Failed to lock perf_event_attr map\n"); 472 return -1; 473 } 474 475 err = bpf_map_lookup_elem(attr_map_fd, &evsel->core.attr, &entry); 476 if (err) { 477 err = bpf_map_update_elem(attr_map_fd, &evsel->core.attr, &entry, BPF_ANY); 478 if (err) 479 goto out; 480 } 481 482 evsel->bperf_leader_link_fd = bpf_link_get_fd_by_id(entry.link_id); 483 if (evsel->bperf_leader_link_fd < 0 && 484 bperf_reload_leader_program(evsel, attr_map_fd, &entry)) { 485 err = -1; 486 goto out; 487 } 488 /* 489 * The bpf_link holds reference to the leader program, and the 490 * leader program holds reference to the maps. Therefore, if 491 * link_id is valid, diff_map_id should also be valid. 492 */ 493 evsel->bperf_leader_prog_fd = bpf_prog_get_fd_by_id( 494 bpf_link_get_prog_id(evsel->bperf_leader_link_fd)); 495 assert(evsel->bperf_leader_prog_fd >= 0); 496 497 diff_map_fd = bpf_map_get_fd_by_id(entry.diff_map_id); 498 assert(diff_map_fd >= 0); 499 500 /* 501 * bperf uses BPF_PROG_TEST_RUN to get accurate reading. Check 502 * whether the kernel support it 503 */ 504 err = bperf_trigger_reading(evsel->bperf_leader_prog_fd, 0); 505 if (err) { 506 pr_err("The kernel does not support test_run for raw_tp BPF programs.\n" 507 "Therefore, --use-bpf might show inaccurate readings\n"); 508 goto out; 509 } 510 511 /* Step 2: load the follower skeleton */ 512 evsel->follower_skel = bperf_follower_bpf__open(); 513 if (!evsel->follower_skel) { 514 err = -1; 515 pr_err("Failed to open follower skeleton\n"); 516 goto out; 517 } 518 519 /* attach fexit program to the leader program */ 520 bpf_program__set_attach_target(evsel->follower_skel->progs.fexit_XXX, 521 evsel->bperf_leader_prog_fd, "on_switch"); 522 523 /* connect to leader diff_reading map */ 524 bpf_map__reuse_fd(evsel->follower_skel->maps.diff_readings, diff_map_fd); 525 526 /* set up reading map */ 527 bpf_map__set_max_entries(evsel->follower_skel->maps.accum_readings, 528 filter_entry_cnt); 529 /* set up follower filter based on target */ 530 bpf_map__set_max_entries(evsel->follower_skel->maps.filter, 531 filter_entry_cnt); 532 err = bperf_follower_bpf__load(evsel->follower_skel); 533 if (err) { 534 pr_err("Failed to load follower skeleton\n"); 535 bperf_follower_bpf__destroy(evsel->follower_skel); 536 evsel->follower_skel = NULL; 537 goto out; 538 } 539 540 for (i = 0; i < filter_entry_cnt; i++) { 541 int filter_map_fd; 542 __u32 key; 543 544 if (filter_type == BPERF_FILTER_PID || 545 filter_type == BPERF_FILTER_TGID) 546 key = perf_thread_map__pid(evsel->core.threads, i); 547 else if (filter_type == BPERF_FILTER_CPU) 548 key = perf_cpu_map__cpu(evsel->core.cpus, i).cpu; 549 else 550 break; 551 552 filter_map_fd = bpf_map__fd(evsel->follower_skel->maps.filter); 553 bpf_map_update_elem(filter_map_fd, &key, &i, BPF_ANY); 554 } 555 556 evsel->follower_skel->bss->type = filter_type; 557 558 err = bperf_follower_bpf__attach(evsel->follower_skel); 559 560 out: 561 if (err && evsel->bperf_leader_link_fd >= 0) 562 close(evsel->bperf_leader_link_fd); 563 if (err && evsel->bperf_leader_prog_fd >= 0) 564 close(evsel->bperf_leader_prog_fd); 565 if (diff_map_fd >= 0) 566 close(diff_map_fd); 567 568 flock(attr_map_fd, LOCK_UN); 569 close(attr_map_fd); 570 571 return err; 572 } 573 574 static int bperf__install_pe(struct evsel *evsel, int cpu_map_idx, int fd) 575 { 576 struct bperf_leader_bpf *skel = evsel->leader_skel; 577 578 return bpf_map_update_elem(bpf_map__fd(skel->maps.events), 579 &cpu_map_idx, &fd, BPF_ANY); 580 } 581 582 /* 583 * trigger the leader prog on each cpu, so the accum_reading map could get 584 * the latest readings. 585 */ 586 static int bperf_sync_counters(struct evsel *evsel) 587 { 588 int num_cpu, i, cpu; 589 590 num_cpu = perf_cpu_map__nr(all_cpu_map); 591 for (i = 0; i < num_cpu; i++) { 592 cpu = perf_cpu_map__cpu(all_cpu_map, i).cpu; 593 bperf_trigger_reading(evsel->bperf_leader_prog_fd, cpu); 594 } 595 return 0; 596 } 597 598 static int bperf__enable(struct evsel *evsel) 599 { 600 evsel->follower_skel->bss->enabled = 1; 601 return 0; 602 } 603 604 static int bperf__disable(struct evsel *evsel) 605 { 606 evsel->follower_skel->bss->enabled = 0; 607 return 0; 608 } 609 610 static int bperf__read(struct evsel *evsel) 611 { 612 struct bperf_follower_bpf *skel = evsel->follower_skel; 613 __u32 num_cpu_bpf = cpu__max_cpu().cpu; 614 struct bpf_perf_event_value values[num_cpu_bpf]; 615 struct perf_counts_values *counts; 616 int reading_map_fd, err = 0; 617 __u32 i; 618 int j; 619 620 bperf_sync_counters(evsel); 621 reading_map_fd = bpf_map__fd(skel->maps.accum_readings); 622 623 for (i = 0; i < bpf_map__max_entries(skel->maps.accum_readings); i++) { 624 struct perf_cpu entry; 625 __u32 cpu; 626 627 err = bpf_map_lookup_elem(reading_map_fd, &i, values); 628 if (err) 629 goto out; 630 switch (evsel->follower_skel->bss->type) { 631 case BPERF_FILTER_GLOBAL: 632 assert(i == 0); 633 634 perf_cpu_map__for_each_cpu(entry, j, evsel__cpus(evsel)) { 635 counts = perf_counts(evsel->counts, j, 0); 636 counts->val = values[entry.cpu].counter; 637 counts->ena = values[entry.cpu].enabled; 638 counts->run = values[entry.cpu].running; 639 } 640 break; 641 case BPERF_FILTER_CPU: 642 cpu = perf_cpu_map__cpu(evsel__cpus(evsel), i).cpu; 643 assert(cpu >= 0); 644 counts = perf_counts(evsel->counts, i, 0); 645 counts->val = values[cpu].counter; 646 counts->ena = values[cpu].enabled; 647 counts->run = values[cpu].running; 648 break; 649 case BPERF_FILTER_PID: 650 case BPERF_FILTER_TGID: 651 counts = perf_counts(evsel->counts, 0, i); 652 counts->val = 0; 653 counts->ena = 0; 654 counts->run = 0; 655 656 for (cpu = 0; cpu < num_cpu_bpf; cpu++) { 657 counts->val += values[cpu].counter; 658 counts->ena += values[cpu].enabled; 659 counts->run += values[cpu].running; 660 } 661 break; 662 default: 663 break; 664 } 665 } 666 out: 667 return err; 668 } 669 670 static int bperf__destroy(struct evsel *evsel) 671 { 672 bperf_follower_bpf__destroy(evsel->follower_skel); 673 close(evsel->bperf_leader_prog_fd); 674 close(evsel->bperf_leader_link_fd); 675 return 0; 676 } 677 678 /* 679 * bperf: share hardware PMCs with BPF 680 * 681 * perf uses performance monitoring counters (PMC) to monitor system 682 * performance. The PMCs are limited hardware resources. For example, 683 * Intel CPUs have 3x fixed PMCs and 4x programmable PMCs per cpu. 684 * 685 * Modern data center systems use these PMCs in many different ways: 686 * system level monitoring, (maybe nested) container level monitoring, per 687 * process monitoring, profiling (in sample mode), etc. In some cases, 688 * there are more active perf_events than available hardware PMCs. To allow 689 * all perf_events to have a chance to run, it is necessary to do expensive 690 * time multiplexing of events. 691 * 692 * On the other hand, many monitoring tools count the common metrics 693 * (cycles, instructions). It is a waste to have multiple tools create 694 * multiple perf_events of "cycles" and occupy multiple PMCs. 695 * 696 * bperf tries to reduce such wastes by allowing multiple perf_events of 697 * "cycles" or "instructions" (at different scopes) to share PMUs. Instead 698 * of having each perf-stat session to read its own perf_events, bperf uses 699 * BPF programs to read the perf_events and aggregate readings to BPF maps. 700 * Then, the perf-stat session(s) reads the values from these BPF maps. 701 * 702 * || 703 * shared progs and maps <- || -> per session progs and maps 704 * || 705 * --------------- || 706 * | perf_events | || 707 * --------------- fexit || ----------------- 708 * | --------||----> | follower prog | 709 * --------------- / || --- ----------------- 710 * cs -> | leader prog |/ ||/ | | 711 * --> --------------- /|| -------------- ------------------ 712 * / | | / || | filter map | | accum_readings | 713 * / ------------ ------------ || -------------- ------------------ 714 * | | prev map | | diff map | || | 715 * | ------------ ------------ || | 716 * \ || | 717 * = \ ==================================================== | ============ 718 * \ / user space 719 * \ / 720 * \ / 721 * BPF_PROG_TEST_RUN BPF_MAP_LOOKUP_ELEM 722 * \ / 723 * \ / 724 * \------ perf-stat ----------------------/ 725 * 726 * The figure above shows the architecture of bperf. Note that the figure 727 * is divided into 3 regions: shared progs and maps (top left), per session 728 * progs and maps (top right), and user space (bottom). 729 * 730 * The leader prog is triggered on each context switch (cs). The leader 731 * prog reads perf_events and stores the difference (current_reading - 732 * previous_reading) to the diff map. For the same metric, e.g. "cycles", 733 * multiple perf-stat sessions share the same leader prog. 734 * 735 * Each perf-stat session creates a follower prog as fexit program to the 736 * leader prog. It is possible to attach up to BPF_MAX_TRAMP_PROGS (38) 737 * follower progs to the same leader prog. The follower prog checks current 738 * task and processor ID to decide whether to add the value from the diff 739 * map to its accumulated reading map (accum_readings). 740 * 741 * Finally, perf-stat user space reads the value from accum_reading map. 742 * 743 * Besides context switch, it is also necessary to trigger the leader prog 744 * before perf-stat reads the value. Otherwise, the accum_reading map may 745 * not have the latest reading from the perf_events. This is achieved by 746 * triggering the event via sys_bpf(BPF_PROG_TEST_RUN) to each CPU. 747 * 748 * Comment before the definition of struct perf_event_attr_map_entry 749 * describes how different sessions of perf-stat share information about 750 * the leader prog. 751 */ 752 753 struct bpf_counter_ops bperf_ops = { 754 .load = bperf__load, 755 .enable = bperf__enable, 756 .disable = bperf__disable, 757 .read = bperf__read, 758 .install_pe = bperf__install_pe, 759 .destroy = bperf__destroy, 760 }; 761 762 extern struct bpf_counter_ops bperf_cgrp_ops; 763 764 static inline bool bpf_counter_skip(struct evsel *evsel) 765 { 766 return evsel->bpf_counter_ops == NULL; 767 } 768 769 int bpf_counter__install_pe(struct evsel *evsel, int cpu_map_idx, int fd) 770 { 771 if (bpf_counter_skip(evsel)) 772 return 0; 773 return evsel->bpf_counter_ops->install_pe(evsel, cpu_map_idx, fd); 774 } 775 776 int bpf_counter__load(struct evsel *evsel, struct target *target) 777 { 778 if (target->bpf_str) 779 evsel->bpf_counter_ops = &bpf_program_profiler_ops; 780 else if (cgrp_event_expanded && target->use_bpf) 781 evsel->bpf_counter_ops = &bperf_cgrp_ops; 782 else if (target->use_bpf || evsel->bpf_counter || 783 evsel__match_bpf_counter_events(evsel->name)) 784 evsel->bpf_counter_ops = &bperf_ops; 785 786 if (evsel->bpf_counter_ops) 787 return evsel->bpf_counter_ops->load(evsel, target); 788 return 0; 789 } 790 791 int bpf_counter__enable(struct evsel *evsel) 792 { 793 if (bpf_counter_skip(evsel)) 794 return 0; 795 return evsel->bpf_counter_ops->enable(evsel); 796 } 797 798 int bpf_counter__disable(struct evsel *evsel) 799 { 800 if (bpf_counter_skip(evsel)) 801 return 0; 802 return evsel->bpf_counter_ops->disable(evsel); 803 } 804 805 int bpf_counter__read(struct evsel *evsel) 806 { 807 if (bpf_counter_skip(evsel)) 808 return -EAGAIN; 809 return evsel->bpf_counter_ops->read(evsel); 810 } 811 812 void bpf_counter__destroy(struct evsel *evsel) 813 { 814 if (bpf_counter_skip(evsel)) 815 return; 816 evsel->bpf_counter_ops->destroy(evsel); 817 evsel->bpf_counter_ops = NULL; 818 evsel->bpf_skel = NULL; 819 } 820