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. 351The format of data in HEADER_BPF_PROG_INFO is as follows: 352 u32 count 353 354 struct perf_bpil { 355 u32 info_len; /* size of struct bpf_prog_info, when the tool is compiled */ 356 u32 data_len; /* total bytes allocated for data, round up to 8 bytes */ 357 u64 arrays; /* which arrays are included in data */ 358 struct bpf_prog_info info; 359 u8 data[]; 360 }[count]; 361 362 HEADER_BPF_BTF = 26, 363 364Contains BPF Type Format (BTF). For more information about BTF, please 365refer to Documentation/bpf/btf.rst. 366 367struct { 368 u32 id; 369 u32 data_size; 370 char data[]; 371}; 372 373 HEADER_COMPRESSED = 27, 374 375struct { 376 u32 version; 377 u32 type; 378 u32 level; 379 u32 ratio; 380 u32 mmap_len; 381}; 382 383Indicates that trace contains records of PERF_RECORD_COMPRESSED2 type 384that have perf_events records in compressed form. 385 386 HEADER_CPU_PMU_CAPS = 28, 387 388 A list of cpu PMU capabilities. The format of data is as below. 389 390struct { 391 u32 nr_cpu_pmu_caps; 392 { 393 char name[]; 394 char value[]; 395 } [nr_cpu_pmu_caps] 396}; 397 398 399Example: 400 cpu pmu capabilities: branches=32, max_precise=3, pmu_name=icelake 401 402 HEADER_CLOCK_DATA = 29, 403 404 Contains clock id and its reference time together with wall clock 405 time taken at the 'same time', both values are in nanoseconds. 406 The format of data is as below. 407 408struct { 409 u32 version; /* version = 1 */ 410 u32 clockid; 411 u64 wall_clock_ns; 412 u64 clockid_time_ns; 413}; 414 415 HEADER_HYBRID_TOPOLOGY = 30, 416 417Indicate the hybrid CPUs. The format of data is as below. 418 419struct { 420 u32 nr; 421 struct { 422 char pmu_name[]; 423 char cpus[]; 424 } [nr]; /* Variable length records */ 425}; 426 427Example: 428 hybrid cpu system: 429 cpu_core cpu list : 0-15 430 cpu_atom cpu list : 16-23 431 432 HEADER_PMU_CAPS = 31, 433 434 List of pmu capabilities (except cpu pmu which is already 435 covered by HEADER_CPU_PMU_CAPS). Note that hybrid cpu pmu 436 capabilities are also stored here. 437 438struct { 439 u32 nr_pmu; 440 struct { 441 u32 nr_caps; 442 { 443 char name[]; 444 char value[]; 445 } [nr_caps]; 446 char pmu_name[]; 447 } [nr_pmu]; 448}; 449 450 other bits are reserved and should ignored for now 451 HEADER_FEAT_BITS = 256, 452 453Attributes 454 455This is an array of perf_event_attrs, each attr_size bytes long, which defines 456each event collected. See perf_event.h or the man page for a detailed 457description. 458 459Data 460 461This section is the bulk of the file. It consist of a stream of perf_events 462describing events. This matches the format generated by the kernel. 463See perf_event.h or the manpage for a detailed description. 464 465Some notes on parsing: 466 467Ordering 468 469The events are not necessarily in time stamp order, as they can be 470collected in parallel on different CPUs. If the events should be 471processed in time order they need to be sorted first. It is possible 472to only do a partial sort using the FINISHED_ROUND event header (see 473below). perf record guarantees that there is no reordering over a 474FINISHED_ROUND. 475 476ID vs IDENTIFIER 477 478When the event stream contains multiple events each event is identified 479by an ID. This can be either through the PERF_SAMPLE_ID or the 480PERF_SAMPLE_IDENTIFIER header. The PERF_SAMPLE_IDENTIFIER header is 481at a fixed offset from the event header, which allows reliable 482parsing of the header. Relying on ID may be ambiguous. 483IDENTIFIER is only supported by newer Linux kernels. 484 485Perf record specific events: 486 487In addition to the kernel generated event types perf record adds its 488own event types (in addition it also synthesizes some kernel events, 489for example MMAP events) 490 491 PERF_RECORD_USER_TYPE_START = 64, 492 PERF_RECORD_HEADER_ATTR = 64, 493 494struct attr_event { 495 struct perf_event_header header; 496 struct perf_event_attr attr; 497 uint64_t id[]; 498}; 499 500 PERF_RECORD_HEADER_EVENT_TYPE = 65, /* deprecated */ 501 502#define MAX_EVENT_NAME 64 503 504struct perf_trace_event_type { 505 uint64_t event_id; 506 char name[MAX_EVENT_NAME]; 507}; 508 509struct event_type_event { 510 struct perf_event_header header; 511 struct perf_trace_event_type event_type; 512}; 513 514 515 PERF_RECORD_HEADER_TRACING_DATA = 66, 516 517Describe me 518 519struct tracing_data_event { 520 struct perf_event_header header; 521 uint32_t size; 522}; 523 524 PERF_RECORD_HEADER_BUILD_ID = 67, 525 526Define a ELF build ID for a referenced executable. 527 528 struct build_id_event; /* See above */ 529 530 PERF_RECORD_FINISHED_ROUND = 68, 531 532No event reordering over this header. No payload. 533 534 PERF_RECORD_ID_INDEX = 69, 535 536Map event ids to CPUs and TIDs. 537 538struct id_index_entry { 539 uint64_t id; 540 uint64_t idx; 541 uint64_t cpu; 542 uint64_t tid; 543}; 544 545struct id_index_event { 546 struct perf_event_header header; 547 uint64_t nr; 548 struct id_index_entry entries[nr]; 549}; 550 551 PERF_RECORD_AUXTRACE_INFO = 70, 552 553Auxtrace type specific information. Describe me 554 555struct auxtrace_info_event { 556 struct perf_event_header header; 557 uint32_t type; 558 uint32_t reserved__; /* For alignment */ 559 uint64_t priv[]; 560}; 561 562 PERF_RECORD_AUXTRACE = 71, 563 564Defines auxtrace data. Followed by the actual data. The contents of 565the auxtrace data is dependent on the event and the CPU. For example 566for Intel Processor Trace it contains Processor Trace data generated 567by the CPU. 568 569struct auxtrace_event { 570 struct perf_event_header header; 571 uint64_t size; 572 uint64_t offset; 573 uint64_t reference; 574 uint32_t idx; 575 uint32_t tid; 576 uint32_t cpu; 577 uint32_t reserved__; /* For alignment */ 578}; 579 580struct aux_event { 581 struct perf_event_header header; 582 uint64_t aux_offset; 583 uint64_t aux_size; 584 uint64_t flags; 585}; 586 587 PERF_RECORD_AUXTRACE_ERROR = 72, 588 589Describes an error in hardware tracing 590 591enum auxtrace_error_type { 592 PERF_AUXTRACE_ERROR_ITRACE = 1, 593 PERF_AUXTRACE_ERROR_MAX 594}; 595 596#define MAX_AUXTRACE_ERROR_MSG 64 597 598struct auxtrace_error_event { 599 struct perf_event_header header; 600 uint32_t type; 601 uint32_t code; 602 uint32_t cpu; 603 uint32_t pid; 604 uint32_t tid; 605 uint32_t reserved__; /* For alignment */ 606 uint64_t ip; 607 char msg[MAX_AUXTRACE_ERROR_MSG]; 608}; 609 610 PERF_RECORD_HEADER_FEATURE = 80, 611 612Describes a header feature. These are records used in pipe-mode that 613contain information that otherwise would be in perf.data file's header. 614 615 PERF_RECORD_COMPRESSED = 81, /* deprecated */ 616 617The header is followed by compressed data frame that can be decompressed 618into array of perf trace records. The size of the entire compressed event 619record including the header is limited by the max value of header.size. 620 621It is deprecated and new files should use PERF_RECORD_COMPRESSED2 to gurantee 6228-byte alignment. 623 624struct compressed_event { 625 struct perf_event_header header; 626 char data[]; 627}; 628 629 PERF_RECORD_FINISHED_INIT = 82, 630 631Marks the end of records for the system, pre-existing threads in system wide 632sessions, etc. Those are the ones prefixed PERF_RECORD_USER_*. 633 634This is used, for instance, to 'perf inject' events after init and before 635regular events, those emitted by the kernel, to support combining guest and 636host records. 637 638 PERF_RECORD_COMPRESSED2 = 83, 639 6408-byte aligned version of `PERF_RECORD_COMPRESSED`. `header.size` indicates the 641total record size, including padding for 8-byte alignment, and `data_size` 642specifies the actual size of the compressed data. 643 644struct perf_record_compressed2 { 645 struct perf_event_header header; 646 __u64 data_size; 647 char data[]; 648}; 649 650Event types 651 652Define the event attributes with their IDs. 653 654An array bound by the perf_file_section size. 655 656 struct { 657 struct perf_event_attr attr; /* Size defined by header.attr_size */ 658 struct perf_file_section ids; 659 } 660 661ids points to a array of uint64_t defining the ids for event attr attr. 662 663Pipe-mode data 664 665Pipe-mode avoid seeks in the file by removing the perf_file_section and flags 666from the struct perf_header. The trimmed header is: 667 668struct perf_pipe_file_header { 669 u64 magic; 670 u64 size; 671}; 672 673The information about attrs, data, and event_types is instead in the 674synthesized events PERF_RECORD_ATTR, PERF_RECORD_HEADER_TRACING_DATA, 675PERF_RECORD_HEADER_EVENT_TYPE, and PERF_RECORD_HEADER_FEATURE 676that are generated by perf record in pipe-mode. 677 678 679References: 680 681include/uapi/linux/perf_event.h 682 683This is the canonical description of the kernel generated perf_events 684and the perf_event_attrs. 685 686perf_events manpage 687 688A manpage describing perf_event and perf_event_attr is here: 689http://web.eece.maine.edu/~vweaver/projects/perf_events/programming.html 690This tends to be slightly behind the kernel include, but has better 691descriptions. An (typically older) version of the man page may be 692included with the standard Linux man pages, available with "man 693perf_events" 694 695pmu-tools 696 697https://github.com/andikleen/pmu-tools/tree/master/parser 698 699A definition of the perf.data format in python "construct" format is available 700in pmu-tools parser. This allows to read perf.data from python and dump it. 701 702quipper 703 704The quipper C++ parser is available at 705http://github.com/google/perf_data_converter/tree/master/src/quipper 706 707