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