1perf.data format 2 3Uptodate as of v4.7 4 5This document describes the on-disk perf.data format, generated by perf record 6or perf inject and consumed by the other perf tools. 7 8On a high level perf.data contains the events generated by the PMUs, plus metadata. 9 10All fields are in native-endian of the machine that generated the perf.data. 11 12When perf is writing to a pipe it uses a special version of the file 13format that does not rely on seeking to adjust data offsets. This 14format is described in "Pipe-mode data" section. The pipe data version can be 15augmented with additional events using perf inject. 16 17The file starts with a perf_header: 18 19struct perf_header { 20 char magic[8]; /* PERFILE2 */ 21 uint64_t size; /* size of the header */ 22 uint64_t attr_size; /* size of an attribute in attrs */ 23 struct perf_file_section attrs; 24 struct perf_file_section data; 25 struct perf_file_section event_types; 26 uint64_t flags; 27 uint64_t flags1[3]; 28}; 29 30The magic number identifies the perf file and the version. Current perf versions 31use PERFILE2. Old perf versions generated a version 1 format (PERFFILE). Version 1 32is not described here. The magic number also identifies the endian. When the 33magic value is 64bit byte swapped compared the file is in non-native 34endian. 35 36A perf_file_section contains a pointer to another section of the perf file. 37The header contains three such pointers: for attributes, data and event types. 38 39struct perf_file_section { 40 uint64_t offset; /* offset from start of file */ 41 uint64_t size; /* size of the section */ 42}; 43 44Flags section: 45 46For each of the optional features a perf_file_section is placed after the data 47section if the feature bit is set in the perf_header flags bitset. The 48respective perf_file_section points to the data of the additional header and 49defines its size. 50 51Some headers consist of strings, which are defined like this: 52 53struct perf_header_string { 54 uint32_t len; 55 char string[len]; /* zero terminated */ 56}; 57 58Some headers consist of a sequence of strings, which start with a 59 60struct perf_header_string_list { 61 uint32_t nr; 62 struct perf_header_string strings[nr]; /* variable length records */ 63}; 64 65The bits are the flags bits in a 256 bit bitmap starting with 66flags. These define the valid bits: 67 68 HEADER_RESERVED = 0, /* always cleared */ 69 HEADER_FIRST_FEATURE = 1, 70 HEADER_TRACING_DATA = 1, 71 72Describe me. 73 74 HEADER_BUILD_ID = 2, 75 76The header consists of an sequence of build_id_event. The size of each record 77is defined by header.size (see perf_event.h). Each event defines a ELF build id 78for a executable file name for a pid. An ELF build id is a unique identifier 79assigned by the linker to an executable. 80 81struct build_id_event { 82 struct perf_event_header header; 83 pid_t pid; 84 uint8_t build_id[24]; 85 char filename[header.size - offsetof(struct build_id_event, filename)]; 86}; 87 88 HEADER_HOSTNAME = 3, 89 90A perf_header_string with the hostname where the data was collected 91(uname -n) 92 93 HEADER_OSRELEASE = 4, 94 95A perf_header_string with the os release where the data was collected 96(uname -r) 97 98 HEADER_VERSION = 5, 99 100A perf_header_string with the perf user tool version where the 101data was collected. This is the same as the version of the source tree 102the perf tool was built from. 103 104 HEADER_ARCH = 6, 105 106A perf_header_string with the CPU architecture (uname -m) 107 108 HEADER_NRCPUS = 7, 109 110A structure defining the number of CPUs. 111 112struct nr_cpus { 113 uint32_t nr_cpus_available; /* CPUs not yet onlined */ 114 uint32_t nr_cpus_online; 115}; 116 117 HEADER_CPUDESC = 8, 118 119A perf_header_string with description of the CPU. On x86 this is the model name 120in /proc/cpuinfo 121 122 HEADER_CPUID = 9, 123 124A perf_header_string with the exact CPU type. On x86 this is 125vendor,family,model,stepping. For example: GenuineIntel,6,69,1 126 127 HEADER_TOTAL_MEM = 10, 128 129An uint64_t with the total memory in kilobytes. 130 131 HEADER_CMDLINE = 11, 132 133A perf_header_string_list with the perf arg-vector used to collect the data. 134 135 HEADER_EVENT_DESC = 12, 136 137Another description of the perf_event_attrs, more detailed than header.attrs 138including IDs and names. See perf_event.h or the man page for a description 139of a struct perf_event_attr. 140 141struct { 142 uint32_t nr; /* number of events */ 143 uint32_t attr_size; /* size of each perf_event_attr */ 144 struct { 145 struct perf_event_attr attr; /* size of attr_size */ 146 uint32_t nr_ids; 147 struct perf_header_string event_string; 148 uint64_t ids[nr_ids]; 149 } events[nr]; /* Variable length records */ 150}; 151 152 HEADER_CPU_TOPOLOGY = 13, 153 154struct { 155 /* 156 * First revision of HEADER_CPU_TOPOLOGY 157 * 158 * See 'struct perf_header_string_list' definition earlier 159 * in this file. 160 */ 161 162 struct perf_header_string_list cores; /* Variable length */ 163 struct perf_header_string_list threads; /* Variable length */ 164 165 /* 166 * Second revision of HEADER_CPU_TOPOLOGY, older tools 167 * will not consider what comes next 168 */ 169 170 struct { 171 uint32_t core_id; 172 uint32_t socket_id; 173 } cpus[nr]; /* Variable length records */ 174 /* 'nr' comes from previously processed HEADER_NRCPUS's nr_cpu_avail */ 175 176 /* 177 * Third revision of HEADER_CPU_TOPOLOGY, older tools 178 * will not consider what comes next 179 */ 180 181 struct perf_header_string_list dies; /* Variable length */ 182 uint32_t die_id[nr_cpus_avail]; /* from previously processed HEADER_NR_CPUS, VLA */ 183}; 184 185Example: 186 sibling sockets : 0-8 187 sibling dies : 0-3 188 sibling dies : 4-7 189 sibling threads : 0-1 190 sibling threads : 2-3 191 sibling threads : 4-5 192 sibling threads : 6-7 193 194 HEADER_NUMA_TOPOLOGY = 14, 195 196 A list of NUMA node descriptions 197 198struct { 199 uint32_t nr; 200 struct { 201 uint32_t nodenr; 202 uint64_t mem_total; 203 uint64_t mem_free; 204 struct perf_header_string cpus; 205 } nodes[nr]; /* Variable length records */ 206}; 207 208 HEADER_BRANCH_STACK = 15, 209 210Not implemented in perf. 211 212 HEADER_PMU_MAPPINGS = 16, 213 214 A list of PMU structures, defining the different PMUs supported by perf. 215 216struct { 217 uint32_t nr; 218 struct pmu { 219 uint32_t pmu_type; 220 struct perf_header_string pmu_name; 221 } [nr]; /* Variable length records */ 222}; 223 224 HEADER_GROUP_DESC = 17, 225 226 Description of counter groups ({...} in perf syntax) 227 228struct { 229 uint32_t nr; 230 struct { 231 struct perf_header_string string; 232 uint32_t leader_idx; 233 uint32_t nr_members; 234 } [nr]; /* Variable length records */ 235}; 236 237 HEADER_AUXTRACE = 18, 238 239Define additional auxtrace areas in the perf.data. auxtrace is used to store 240undecoded hardware tracing information, such as Intel Processor Trace data. 241 242/** 243 * struct auxtrace_index_entry - indexes a AUX area tracing event within a 244 * perf.data file. 245 * @file_offset: offset within the perf.data file 246 * @sz: size of the event 247 */ 248struct auxtrace_index_entry { 249 u64 file_offset; 250 u64 sz; 251}; 252 253#define PERF_AUXTRACE_INDEX_ENTRY_COUNT 256 254 255/** 256 * struct auxtrace_index - index of AUX area tracing events within a perf.data 257 * file. 258 * @list: linking a number of arrays of entries 259 * @nr: number of entries 260 * @entries: array of entries 261 */ 262struct auxtrace_index { 263 struct list_head list; 264 size_t nr; 265 struct auxtrace_index_entry entries[PERF_AUXTRACE_INDEX_ENTRY_COUNT]; 266}; 267 268 HEADER_STAT = 19, 269 270This is merely a flag signifying that the data section contains data 271recorded from perf stat record. 272 273 HEADER_CACHE = 20, 274 275Description of the cache hierarchy. Based on the Linux sysfs format 276in /sys/devices/system/cpu/cpu*/cache/ 277 278 u32 version Currently always 1 279 u32 number_of_cache_levels 280 281struct { 282 u32 level; 283 u32 line_size; 284 u32 sets; 285 u32 ways; 286 struct perf_header_string type; 287 struct perf_header_string size; 288 struct perf_header_string map; 289}[number_of_cache_levels]; 290 291 HEADER_SAMPLE_TIME = 21, 292 293Two uint64_t for the time of first sample and the time of last sample. 294 295 HEADER_SAMPLE_TOPOLOGY = 22, 296 297Physical memory map and its node assignments. 298 299The format of data in MEM_TOPOLOGY is as follows: 300 301 u64 version; // Currently 1 302 u64 block_size_bytes; // /sys/devices/system/memory/block_size_bytes 303 u64 count; // number of nodes 304 305struct memory_node { 306 u64 node_id; // node index 307 u64 size; // size of bitmap 308 struct bitmap { 309 /* size of bitmap again */ 310 u64 bitmapsize; 311 /* bitmap of memory indexes that belongs to node */ 312 /* /sys/devices/system/node/node<NODE>/memory<INDEX> */ 313 u64 entries[(bitmapsize/64)+1]; 314 } 315}[count]; 316 317The MEM_TOPOLOGY can be displayed with following command: 318 319$ perf report --header-only -I 320... 321# memory nodes (nr 1, block size 0x8000000): 322# 0 [7G]: 0-23,32-69 323 324 HEADER_CLOCKID = 23, 325 326One uint64_t for the clockid frequency, specified, for instance, via 'perf 327record -k' (see clock_gettime()), to enable timestamps derived metrics 328conversion into wall clock time on the reporting stage. 329 330 HEADER_DIR_FORMAT = 24, 331 332The data files layout is described by HEADER_DIR_FORMAT feature. Currently it 333holds only version number (1): 334 335 uint64_t version; 336 337The current version holds only version value (1) means that data files: 338 339- Follow the 'data.*' name format. 340 341- Contain raw events data in standard perf format as read from kernel (and need 342 to be sorted) 343 344Future versions are expected to describe different data files layout according 345to special needs. 346 347 HEADER_BPF_PROG_INFO = 25, 348 349struct perf_bpil, which contains detailed information about 350a BPF program, including type, id, tag, jited/xlated instructions, etc. 351 352 HEADER_BPF_BTF = 26, 353 354Contains BPF Type Format (BTF). For more information about BTF, please 355refer to Documentation/bpf/btf.rst. 356 357struct { 358 u32 id; 359 u32 data_size; 360 char data[]; 361}; 362 363 HEADER_COMPRESSED = 27, 364 365struct { 366 u32 version; 367 u32 type; 368 u32 level; 369 u32 ratio; 370 u32 mmap_len; 371}; 372 373Indicates that trace contains records of PERF_RECORD_COMPRESSED type 374that have perf_events records in compressed form. 375 376 HEADER_CPU_PMU_CAPS = 28, 377 378 A list of cpu PMU capabilities. The format of data is as below. 379 380struct { 381 u32 nr_cpu_pmu_caps; 382 { 383 char name[]; 384 char value[]; 385 } [nr_cpu_pmu_caps] 386}; 387 388 389Example: 390 cpu pmu capabilities: branches=32, max_precise=3, pmu_name=icelake 391 392 HEADER_CLOCK_DATA = 29, 393 394 Contains clock id and its reference time together with wall clock 395 time taken at the 'same time', both values are in nanoseconds. 396 The format of data is as below. 397 398struct { 399 u32 version; /* version = 1 */ 400 u32 clockid; 401 u64 wall_clock_ns; 402 u64 clockid_time_ns; 403}; 404 405 HEADER_HYBRID_TOPOLOGY = 30, 406 407Indicate the hybrid CPUs. The format of data is as below. 408 409struct { 410 u32 nr; 411 struct { 412 char pmu_name[]; 413 char cpus[]; 414 } [nr]; /* Variable length records */ 415}; 416 417Example: 418 hybrid cpu system: 419 cpu_core cpu list : 0-15 420 cpu_atom cpu list : 16-23 421 422 HEADER_PMU_CAPS = 31, 423 424 List of pmu capabilities (except cpu pmu which is already 425 covered by HEADER_CPU_PMU_CAPS). Note that hybrid cpu pmu 426 capabilities are also stored here. 427 428struct { 429 u32 nr_pmu; 430 struct { 431 u32 nr_caps; 432 { 433 char name[]; 434 char value[]; 435 } [nr_caps]; 436 char pmu_name[]; 437 } [nr_pmu]; 438}; 439 440 other bits are reserved and should ignored for now 441 HEADER_FEAT_BITS = 256, 442 443Attributes 444 445This is an array of perf_event_attrs, each attr_size bytes long, which defines 446each event collected. See perf_event.h or the man page for a detailed 447description. 448 449Data 450 451This section is the bulk of the file. It consist of a stream of perf_events 452describing events. This matches the format generated by the kernel. 453See perf_event.h or the manpage for a detailed description. 454 455Some notes on parsing: 456 457Ordering 458 459The events are not necessarily in time stamp order, as they can be 460collected in parallel on different CPUs. If the events should be 461processed in time order they need to be sorted first. It is possible 462to only do a partial sort using the FINISHED_ROUND event header (see 463below). perf record guarantees that there is no reordering over a 464FINISHED_ROUND. 465 466ID vs IDENTIFIER 467 468When the event stream contains multiple events each event is identified 469by an ID. This can be either through the PERF_SAMPLE_ID or the 470PERF_SAMPLE_IDENTIFIER header. The PERF_SAMPLE_IDENTIFIER header is 471at a fixed offset from the event header, which allows reliable 472parsing of the header. Relying on ID may be ambiguous. 473IDENTIFIER is only supported by newer Linux kernels. 474 475Perf record specific events: 476 477In addition to the kernel generated event types perf record adds its 478own event types (in addition it also synthesizes some kernel events, 479for example MMAP events) 480 481 PERF_RECORD_USER_TYPE_START = 64, 482 PERF_RECORD_HEADER_ATTR = 64, 483 484struct attr_event { 485 struct perf_event_header header; 486 struct perf_event_attr attr; 487 uint64_t id[]; 488}; 489 490 PERF_RECORD_HEADER_EVENT_TYPE = 65, /* deprecated */ 491 492#define MAX_EVENT_NAME 64 493 494struct perf_trace_event_type { 495 uint64_t event_id; 496 char name[MAX_EVENT_NAME]; 497}; 498 499struct event_type_event { 500 struct perf_event_header header; 501 struct perf_trace_event_type event_type; 502}; 503 504 505 PERF_RECORD_HEADER_TRACING_DATA = 66, 506 507Describe me 508 509struct tracing_data_event { 510 struct perf_event_header header; 511 uint32_t size; 512}; 513 514 PERF_RECORD_HEADER_BUILD_ID = 67, 515 516Define a ELF build ID for a referenced executable. 517 518 struct build_id_event; /* See above */ 519 520 PERF_RECORD_FINISHED_ROUND = 68, 521 522No event reordering over this header. No payload. 523 524 PERF_RECORD_ID_INDEX = 69, 525 526Map event ids to CPUs and TIDs. 527 528struct id_index_entry { 529 uint64_t id; 530 uint64_t idx; 531 uint64_t cpu; 532 uint64_t tid; 533}; 534 535struct id_index_event { 536 struct perf_event_header header; 537 uint64_t nr; 538 struct id_index_entry entries[nr]; 539}; 540 541 PERF_RECORD_AUXTRACE_INFO = 70, 542 543Auxtrace type specific information. Describe me 544 545struct auxtrace_info_event { 546 struct perf_event_header header; 547 uint32_t type; 548 uint32_t reserved__; /* For alignment */ 549 uint64_t priv[]; 550}; 551 552 PERF_RECORD_AUXTRACE = 71, 553 554Defines auxtrace data. Followed by the actual data. The contents of 555the auxtrace data is dependent on the event and the CPU. For example 556for Intel Processor Trace it contains Processor Trace data generated 557by the CPU. 558 559struct auxtrace_event { 560 struct perf_event_header header; 561 uint64_t size; 562 uint64_t offset; 563 uint64_t reference; 564 uint32_t idx; 565 uint32_t tid; 566 uint32_t cpu; 567 uint32_t reserved__; /* For alignment */ 568}; 569 570struct aux_event { 571 struct perf_event_header header; 572 uint64_t aux_offset; 573 uint64_t aux_size; 574 uint64_t flags; 575}; 576 577 PERF_RECORD_AUXTRACE_ERROR = 72, 578 579Describes an error in hardware tracing 580 581enum auxtrace_error_type { 582 PERF_AUXTRACE_ERROR_ITRACE = 1, 583 PERF_AUXTRACE_ERROR_MAX 584}; 585 586#define MAX_AUXTRACE_ERROR_MSG 64 587 588struct auxtrace_error_event { 589 struct perf_event_header header; 590 uint32_t type; 591 uint32_t code; 592 uint32_t cpu; 593 uint32_t pid; 594 uint32_t tid; 595 uint32_t reserved__; /* For alignment */ 596 uint64_t ip; 597 char msg[MAX_AUXTRACE_ERROR_MSG]; 598}; 599 600 PERF_RECORD_HEADER_FEATURE = 80, 601 602Describes a header feature. These are records used in pipe-mode that 603contain information that otherwise would be in perf.data file's header. 604 605 PERF_RECORD_COMPRESSED = 81, 606 607struct compressed_event { 608 struct perf_event_header header; 609 char data[]; 610}; 611 612 PERF_RECORD_FINISHED_INIT = 82, 613 614Marks the end of records for the system, pre-existing threads in system wide 615sessions, etc. Those are the ones prefixed PERF_RECORD_USER_*. 616 617This is used, for instance, to 'perf inject' events after init and before 618regular events, those emitted by the kernel, to support combining guest and 619host records. 620 621 622The header is followed by compressed data frame that can be decompressed 623into array of perf trace records. The size of the entire compressed event 624record including the header is limited by the max value of header.size. 625 626Event types 627 628Define the event attributes with their IDs. 629 630An array bound by the perf_file_section size. 631 632 struct { 633 struct perf_event_attr attr; /* Size defined by header.attr_size */ 634 struct perf_file_section ids; 635 } 636 637ids points to a array of uint64_t defining the ids for event attr attr. 638 639Pipe-mode data 640 641Pipe-mode avoid seeks in the file by removing the perf_file_section and flags 642from the struct perf_header. The trimmed header is: 643 644struct perf_pipe_file_header { 645 u64 magic; 646 u64 size; 647}; 648 649The information about attrs, data, and event_types is instead in the 650synthesized events PERF_RECORD_ATTR, PERF_RECORD_HEADER_TRACING_DATA, 651PERF_RECORD_HEADER_EVENT_TYPE, and PERF_RECORD_HEADER_FEATURE 652that are generated by perf record in pipe-mode. 653 654 655References: 656 657include/uapi/linux/perf_event.h 658 659This is the canonical description of the kernel generated perf_events 660and the perf_event_attrs. 661 662perf_events manpage 663 664A manpage describing perf_event and perf_event_attr is here: 665http://web.eece.maine.edu/~vweaver/projects/perf_events/programming.html 666This tends to be slightly behind the kernel include, but has better 667descriptions. An (typically older) version of the man page may be 668included with the standard Linux man pages, available with "man 669perf_events" 670 671pmu-tools 672 673https://github.com/andikleen/pmu-tools/tree/master/parser 674 675A definition of the perf.data format in python "construct" format is available 676in pmu-tools parser. This allows to read perf.data from python and dump it. 677 678quipper 679 680The quipper C++ parser is available at 681http://github.com/google/perf_data_converter/tree/master/src/quipper 682 683