liblttng-ust/lttng-context-perf-counters.c

   1 /*
   2  * lttng-context-perf-counters.c
   3  *
   4  * LTTng UST performance monitoring counters (perf-counters) integration.
   5  *
   6  * Copyright (C) 2009-2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _LGPL_SOURCE
  24 #include <sys/types.h>
  25 #include <unistd.h>
  26 #include <string.h>
  27 #include <stdlib.h>
  28 #include <stdio.h>
  29 #include <stdbool.h>
  30 #include <sys/mman.h>
  31 #include <sys/syscall.h>
  32 #include <lttng/ust-events.h>
  33 #include <lttng/ust-tracer.h>
  34 #include <lttng/ringbuffer-config.h>
  35 #include <urcu/system.h>
  36 #include <urcu/arch.h>
  37 #include <urcu/rculist.h>
  38 #include <helper.h>
  39 #include <urcu/ref.h>
  40 #include <usterr-signal-safe.h>
  41 #include <signal.h>
  42 #include "perf_event.h"
  43 #include "lttng-tracer-core.h"
  44
  45 /*
  46  * We use a global perf counter key and iterate on per-thread RCU lists
  47  * of fields in the fast path, even though this is not strictly speaking
  48  * what would provide the best fast-path complexity, to ensure teardown
  49  * of sessions vs thread exit is handled racelessly.
  50  *
  51  * Updates and traversals of thread_list are protected by UST lock.
  52  * Updates to rcu_field_list are protected by UST lock.
  53  */
  54
  55 struct lttng_perf_counter_thread_field {
  56         struct lttng_perf_counter_field *field; /* Back reference */
  57         struct perf_event_mmap_page *pc;
  58         struct cds_list_head thread_field_node; /* Per-field list of thread fields (node) */
  59         struct cds_list_head rcu_field_node;    /* RCU per-thread list of fields (node) */
  60         int fd;                                 /* Perf FD */
  61 };
  62
  63 struct lttng_perf_counter_thread {
  64         struct cds_list_head rcu_field_list;    /* RCU per-thread list of fields */
  65 };
  66
  67 struct lttng_perf_counter_field {
  68         struct perf_event_attr attr;
  69         struct cds_list_head thread_field_list; /* Per-field list of thread fields */
  70 };
  71
  72 static pthread_key_t perf_counter_key;
  73
  74 static
  75 size_t perf_counter_get_size(struct lttng_ctx_field *field, size_t offset)
  76 {
  77         size_t size = 0;
  78
  79         size += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
  80         size += sizeof(uint64_t);
  81         return size;
  82 }
  83
  84 static
  85 uint64_t read_perf_counter_syscall(
  86                 struct lttng_perf_counter_thread_field *thread_field)
  87 {
  88         uint64_t count;
  89
  90         if (caa_unlikely(thread_field->fd < 0))
  91                 return 0;
  92
  93         if (caa_unlikely(read(thread_field->fd, &count, sizeof(count))
  94                                 < sizeof(count)))
  95                 return 0;
  96
  97         return count;
  98 }
  99
 100 #if defined(__x86_64__) || defined(__i386__)
 101
 102 static
 103 uint64_t rdpmc(unsigned int counter)
 104 {
 105         unsigned int low, high;
 106
 107         asm volatile("rdpmc" : "=a" (low), "=d" (high) : "c" (counter));
 108
 109         return low | ((uint64_t) high) << 32;
 110 }
 111
 112 static
 113 bool has_rdpmc(struct perf_event_mmap_page *pc)
 114 {
 115         if (caa_unlikely(!pc->cap_bit0_is_deprecated))
 116                 return false;
 117         /* Since Linux kernel 3.12. */
 118         return pc->cap_user_rdpmc;
 119 }
 120
 121 static
 122 uint64_t arch_read_perf_counter(
 123                 struct lttng_perf_counter_thread_field *thread_field)
 124 {
 125         uint32_t seq, idx;
 126         uint64_t count;
 127         struct perf_event_mmap_page *pc = thread_field->pc;
 128
 129         if (caa_unlikely(!pc))
 130                 return 0;
 131
 132         do {
 133                 seq = CMM_LOAD_SHARED(pc->lock);
 134                 cmm_barrier();
 135
 136                 idx = pc->index;
 137                 if (caa_likely(has_rdpmc(pc) && idx)) {
 138                         int64_t pmcval;
 139
 140                         pmcval = rdpmc(idx - 1);
 141                         /* Sign-extend the pmc register result. */
 142                         pmcval <<= 64 - pc->pmc_width;
 143                         pmcval >>= 64 - pc->pmc_width;
 144                         count = pc->offset + pmcval;
 145                 } else {
 146                         /* Fall-back on system call if rdpmc cannot be used. */
 147                         return read_perf_counter_syscall(thread_field);
 148                 }
 149                 cmm_barrier();
 150         } while (CMM_LOAD_SHARED(pc->lock) != seq);
 151
 152         return count;
 153 }
 154
 155 static
 156 int arch_perf_keep_fd(struct lttng_perf_counter_thread_field *thread_field)
 157 {
 158         struct perf_event_mmap_page *pc = thread_field->pc;
 159
 160         if (!pc)
 161                 return 0;
 162         return !has_rdpmc(pc);
 163 }
 164
 165 #else
 166
 167 /* Generic (slow) implementation using a read system call. */
 168 static
 169 uint64_t arch_read_perf_counter(
 170                 struct lttng_perf_counter_thread_field *thread_field)
 171 {
 172         return read_perf_counter_syscall(thread_field);
 173 }
 174
 175 static
 176 int arch_perf_keep_fd(struct lttng_perf_counter_thread_field *thread_field)
 177 {
 178         return 1;
 179 }
 180
 181 #endif
 182
 183 static
 184 int sys_perf_event_open(struct perf_event_attr *attr,
 185                 pid_t pid, int cpu, int group_fd,
 186                 unsigned long flags)
 187 {
 188         return syscall(SYS_perf_event_open, attr, pid, cpu,
 189                         group_fd, flags);
 190 }
 191
 192 static
 193 int open_perf_fd(struct perf_event_attr *attr)
 194 {
 195         int fd;
 196
 197         fd = sys_perf_event_open(attr, 0, -1, -1, 0);
 198         if (fd < 0)
 199                 return -1;
 200
 201         return fd;
 202 }
 203
 204 static
 205 void close_perf_fd(int fd)
 206 {
 207         int ret;
 208
 209         if (fd < 0)
 210                 return;
 211
 212         ret = close(fd);
 213         if (ret) {
 214                 perror("Error closing LTTng-UST perf memory mapping FD");
 215         }
 216 }
 217
 218 static void setup_perf(struct lttng_perf_counter_thread_field *thread_field)
 219 {
 220         void *perf_addr;
 221
 222         perf_addr = mmap(NULL, sizeof(struct perf_event_mmap_page),
 223                         PROT_READ, MAP_SHARED, thread_field->fd, 0);
 224         if (perf_addr == MAP_FAILED)
 225                 perf_addr = NULL;
 226         thread_field->pc = perf_addr;
 227
 228         if (!arch_perf_keep_fd(thread_field)) {
 229                 close_perf_fd(thread_field->fd);
 230                 thread_field->fd = -1;
 231         }
 232 }
 233
 234 static
 235 void unmap_perf_page(struct perf_event_mmap_page *pc)
 236 {
 237         int ret;
 238
 239         if (!pc)
 240                 return;
 241         ret = munmap(pc, sizeof(struct perf_event_mmap_page));
 242         if (ret < 0) {
 243                 PERROR("Error in munmap");
 244                 abort();
 245         }
 246 }
 247
 248 static
 249 struct lttng_perf_counter_thread *alloc_perf_counter_thread(void)
 250 {
 251         struct lttng_perf_counter_thread *perf_thread;
 252         sigset_t newmask, oldmask;
 253         int ret;
 254
 255         ret = sigfillset(&newmask);
 256         if (ret)
 257                 abort();
 258         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 259         if (ret)
 260                 abort();
 261         /* Check again with signals disabled */
 262         perf_thread = pthread_getspecific(perf_counter_key);
 263         if (perf_thread)
 264                 goto skip;
 265         perf_thread = zmalloc(sizeof(*perf_thread));
 266         if (!perf_thread)
 267                 abort();
 268         CDS_INIT_LIST_HEAD(&perf_thread->rcu_field_list);
 269         ret = pthread_setspecific(perf_counter_key, perf_thread);
 270         if (ret)
 271                 abort();
 272 skip:
 273         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 274         if (ret)
 275                 abort();
 276         return perf_thread;
 277 }
 278
 279 static
 280 struct lttng_perf_counter_thread_field *
 281         add_thread_field(struct lttng_perf_counter_field *perf_field,
 282                 struct lttng_perf_counter_thread *perf_thread)
 283 {
 284         struct lttng_perf_counter_thread_field *thread_field;
 285         sigset_t newmask, oldmask;
 286         int ret;
 287
 288         ret = sigfillset(&newmask);
 289         if (ret)
 290                 abort();
 291         ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
 292         if (ret)
 293                 abort();
 294         /* Check again with signals disabled */
 295         cds_list_for_each_entry_rcu(thread_field, &perf_thread->rcu_field_list,
 296                         rcu_field_node) {
 297                 if (thread_field->field == perf_field)
 298                         goto skip;
 299         }
 300         thread_field = zmalloc(sizeof(*thread_field));
 301         if (!thread_field)
 302                 abort();
 303         thread_field->field = perf_field;
 304         thread_field->fd = open_perf_fd(&perf_field->attr);
 305         if (thread_field->fd >= 0)
 306                 setup_perf(thread_field);
 307         /*
 308          * Note: thread_field->pc can be NULL if setup_perf() fails.
 309          * Also, thread_field->fd can be -1 if open_perf_fd() fails.
 310          */
 311         ust_lock_nocheck();
 312         cds_list_add_rcu(&thread_field->rcu_field_node,
 313                         &perf_thread->rcu_field_list);
 314         cds_list_add(&thread_field->thread_field_node,
 315                         &perf_field->thread_field_list);
 316         ust_unlock();
 317 skip:
 318         ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
 319         if (ret)
 320                 abort();
 321         return thread_field;
 322 }
 323
 324 static
 325 struct lttng_perf_counter_thread_field *
 326                 get_thread_field(struct lttng_perf_counter_field *field)
 327 {
 328         struct lttng_perf_counter_thread *perf_thread;
 329         struct lttng_perf_counter_thread_field *thread_field;
 330
 331         perf_thread = pthread_getspecific(perf_counter_key);
 332         if (!perf_thread)
 333                 perf_thread = alloc_perf_counter_thread();
 334         cds_list_for_each_entry_rcu(thread_field, &perf_thread->rcu_field_list,
 335                         rcu_field_node) {
 336                 if (thread_field->field == field)
 337                         return thread_field;
 338         }
 339         /* perf_counter_thread_field not found, need to add one */
 340         return add_thread_field(field, perf_thread);
 341 }
 342
 343 static
 344 uint64_t wrapper_perf_counter_read(struct lttng_ctx_field *field)
 345 {
 346         struct lttng_perf_counter_field *perf_field;
 347         struct lttng_perf_counter_thread_field *perf_thread_field;
 348
 349         perf_field = field->u.perf_counter;
 350         perf_thread_field = get_thread_field(perf_field);
 351         return arch_read_perf_counter(perf_thread_field);
 352 }
 353
 354 static
 355 void perf_counter_record(struct lttng_ctx_field *field,
 356                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
 357                  struct lttng_channel *chan)
 358 {
 359         uint64_t value;
 360
 361         value = wrapper_perf_counter_read(field);
 362         lib_ring_buffer_align_ctx(ctx, lttng_alignof(value));
 363         chan->ops->event_write(ctx, &value, sizeof(value));
 364 }
 365
 366 static
 367 void perf_counter_get_value(struct lttng_ctx_field *field,
 368                 struct lttng_ctx_value *value)
 369 {
 370         value->u.s64 = wrapper_perf_counter_read(field);
 371 }
 372
 373 /* Called with UST lock held */
 374 static
 375 void lttng_destroy_perf_thread_field(
 376                 struct lttng_perf_counter_thread_field *thread_field)
 377 {
 378         close_perf_fd(thread_field->fd);
 379         unmap_perf_page(thread_field->pc);
 380         cds_list_del_rcu(&thread_field->rcu_field_node);
 381         cds_list_del(&thread_field->thread_field_node);
 382         free(thread_field);
 383 }
 384
 385 static
 386 void lttng_destroy_perf_thread_key(void *_key)
 387 {
 388         struct lttng_perf_counter_thread *perf_thread = _key;
 389         struct lttng_perf_counter_thread_field *pos, *p;
 390
 391         ust_lock_nocheck();
 392         cds_list_for_each_entry_safe(pos, p, &perf_thread->rcu_field_list,
 393                         rcu_field_node)
 394                 lttng_destroy_perf_thread_field(pos);
 395         ust_unlock();
 396         free(perf_thread);
 397 }
 398
 399 /* Called with UST lock held */
 400 static
 401 void lttng_destroy_perf_counter_field(struct lttng_ctx_field *field)
 402 {
 403         struct lttng_perf_counter_field *perf_field;
 404         struct lttng_perf_counter_thread_field *pos, *p;
 405
 406         free((char *) field->event_field.name);
 407         perf_field = field->u.perf_counter;
 408         /*
 409          * This put is performed when no threads can concurrently
 410          * perform a "get" concurrently, thanks to urcu-bp grace
 411          * period.
 412          */
 413         cds_list_for_each_entry_safe(pos, p, &perf_field->thread_field_list,
 414                         thread_field_node)
 415                 lttng_destroy_perf_thread_field(pos);
 416         free(perf_field);
 417 }
 418
 419 #ifdef __ARM_ARCH_7A__
 420
 421 static
 422 int perf_get_exclude_kernel(void)
 423 {
 424         return 0;
 425 }
 426
 427 #else /* __ARM_ARCH_7A__ */
 428
 429 static
 430 int perf_get_exclude_kernel(void)
 431 {
 432         return 1;
 433 }
 434
 435 #endif /* __ARM_ARCH_7A__ */
 436
 437 /* Called with UST lock held */
 438 int lttng_add_perf_counter_to_ctx(uint32_t type,
 439                                 uint64_t config,
 440                                 const char *name,
 441                                 struct lttng_ctx **ctx)
 442 {
 443         struct lttng_ctx_field *field;
 444         struct lttng_perf_counter_field *perf_field;
 445         char *name_alloc;
 446         int ret;
 447
 448         name_alloc = strdup(name);
 449         if (!name_alloc) {
 450                 ret = -ENOMEM;
 451                 goto name_alloc_error;
 452         }
 453         perf_field = zmalloc(sizeof(*perf_field));
 454         if (!perf_field) {
 455                 ret = -ENOMEM;
 456                 goto perf_field_alloc_error;
 457         }
 458         field = lttng_append_context(ctx);
 459         if (!field) {
 460                 ret = -ENOMEM;
 461                 goto append_context_error;
 462         }
 463         if (lttng_find_context(*ctx, name_alloc)) {
 464                 ret = -EEXIST;
 465                 goto find_error;
 466         }
 467
 468         field->destroy = lttng_destroy_perf_counter_field;
 469
 470         field->event_field.name = name_alloc;
 471         field->event_field.type.atype = atype_integer;
 472         field->event_field.type.u.basic.integer.size =
 473                         sizeof(uint64_t) * CHAR_BIT;
 474         field->event_field.type.u.basic.integer.alignment =
 475                         lttng_alignof(uint64_t) * CHAR_BIT;
 476         field->event_field.type.u.basic.integer.signedness =
 477                         lttng_is_signed_type(uint64_t);
 478         field->event_field.type.u.basic.integer.reverse_byte_order = 0;
 479         field->event_field.type.u.basic.integer.base = 10;
 480         field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
 481         field->get_size = perf_counter_get_size;
 482         field->record = perf_counter_record;
 483         field->get_value = perf_counter_get_value;
 484
 485         perf_field->attr.type = type;
 486         perf_field->attr.config = config;
 487         perf_field->attr.exclude_kernel = perf_get_exclude_kernel();
 488         CDS_INIT_LIST_HEAD(&perf_field->thread_field_list);
 489         field->u.perf_counter = perf_field;
 490
 491         /* Ensure that this perf counter can be used in this process. */
 492         ret = open_perf_fd(&perf_field->attr);
 493         if (ret < 0) {
 494                 ret = -ENODEV;
 495                 goto setup_error;
 496         }
 497         close_perf_fd(ret);
 498
 499         /*
 500          * Contexts can only be added before tracing is started, so we
 501          * don't have to synchronize against concurrent threads using
 502          * the field here.
 503          */
 504
 505         lttng_context_update(*ctx);
 506         return 0;
 507
 508 setup_error:
 509 find_error:
 510         lttng_remove_context_field(ctx, field);
 511 append_context_error:
 512         free(perf_field);
 513 perf_field_alloc_error:
 514         free(name_alloc);
 515 name_alloc_error:
 516         return ret;
 517 }
 518
 519 int lttng_perf_counter_init(void)
 520 {
 521         int ret;
 522
 523         ret = pthread_key_create(&perf_counter_key,
 524                         lttng_destroy_perf_thread_key);
 525         if (ret)
 526                 ret = -ret;
 527         return ret;
 528 }
 529
 530 void lttng_perf_counter_exit(void)
 531 {
 532         int ret;
 533
 534         ret = pthread_key_delete(perf_counter_key);
 535         if (ret) {
 536                 errno = ret;
 537                 PERROR("Error in pthread_key_delete");
 538         }
 539 }