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 it 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 bpf_prog_info_linear, 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 other bits are reserved and should ignored for now 377 HEADER_FEAT_BITS = 256, 378 379Attributes 380 381This is an array of perf_event_attrs, each attr_size bytes long, which defines 382each event collected. See perf_event.h or the man page for a detailed 383description. 384 385Data 386 387This section is the bulk of the file. It consist of a stream of perf_events 388describing events. This matches the format generated by the kernel. 389See perf_event.h or the manpage for a detailed description. 390 391Some notes on parsing: 392 393Ordering 394 395The events are not necessarily in time stamp order, as they can be 396collected in parallel on different CPUs. If the events should be 397processed in time order they need to be sorted first. It is possible 398to only do a partial sort using the FINISHED_ROUND event header (see 399below). perf record guarantees that there is no reordering over a 400FINISHED_ROUND. 401 402ID vs IDENTIFIER 403 404When the event stream contains multiple events each event is identified 405by an ID. This can be either through the PERF_SAMPLE_ID or the 406PERF_SAMPLE_IDENTIFIER header. The PERF_SAMPLE_IDENTIFIER header is 407at a fixed offset from the event header, which allows reliable 408parsing of the header. Relying on ID may be ambiguous. 409IDENTIFIER is only supported by newer Linux kernels. 410 411Perf record specific events: 412 413In addition to the kernel generated event types perf record adds its 414own event types (in addition it also synthesizes some kernel events, 415for example MMAP events) 416 417 PERF_RECORD_USER_TYPE_START = 64, 418 PERF_RECORD_HEADER_ATTR = 64, 419 420struct attr_event { 421 struct perf_event_header header; 422 struct perf_event_attr attr; 423 uint64_t id[]; 424}; 425 426 PERF_RECORD_HEADER_EVENT_TYPE = 65, /* deprecated */ 427 428#define MAX_EVENT_NAME 64 429 430struct perf_trace_event_type { 431 uint64_t event_id; 432 char name[MAX_EVENT_NAME]; 433}; 434 435struct event_type_event { 436 struct perf_event_header header; 437 struct perf_trace_event_type event_type; 438}; 439 440 441 PERF_RECORD_HEADER_TRACING_DATA = 66, 442 443Describe me 444 445struct tracing_data_event { 446 struct perf_event_header header; 447 uint32_t size; 448}; 449 450 PERF_RECORD_HEADER_BUILD_ID = 67, 451 452Define a ELF build ID for a referenced executable. 453 454 struct build_id_event; /* See above */ 455 456 PERF_RECORD_FINISHED_ROUND = 68, 457 458No event reordering over this header. No payload. 459 460 PERF_RECORD_ID_INDEX = 69, 461 462Map event ids to CPUs and TIDs. 463 464struct id_index_entry { 465 uint64_t id; 466 uint64_t idx; 467 uint64_t cpu; 468 uint64_t tid; 469}; 470 471struct id_index_event { 472 struct perf_event_header header; 473 uint64_t nr; 474 struct id_index_entry entries[nr]; 475}; 476 477 PERF_RECORD_AUXTRACE_INFO = 70, 478 479Auxtrace type specific information. Describe me 480 481struct auxtrace_info_event { 482 struct perf_event_header header; 483 uint32_t type; 484 uint32_t reserved__; /* For alignment */ 485 uint64_t priv[]; 486}; 487 488 PERF_RECORD_AUXTRACE = 71, 489 490Defines auxtrace data. Followed by the actual data. The contents of 491the auxtrace data is dependent on the event and the CPU. For example 492for Intel Processor Trace it contains Processor Trace data generated 493by the CPU. 494 495struct auxtrace_event { 496 struct perf_event_header header; 497 uint64_t size; 498 uint64_t offset; 499 uint64_t reference; 500 uint32_t idx; 501 uint32_t tid; 502 uint32_t cpu; 503 uint32_t reserved__; /* For alignment */ 504}; 505 506struct aux_event { 507 struct perf_event_header header; 508 uint64_t aux_offset; 509 uint64_t aux_size; 510 uint64_t flags; 511}; 512 513 PERF_RECORD_AUXTRACE_ERROR = 72, 514 515Describes an error in hardware tracing 516 517enum auxtrace_error_type { 518 PERF_AUXTRACE_ERROR_ITRACE = 1, 519 PERF_AUXTRACE_ERROR_MAX 520}; 521 522#define MAX_AUXTRACE_ERROR_MSG 64 523 524struct auxtrace_error_event { 525 struct perf_event_header header; 526 uint32_t type; 527 uint32_t code; 528 uint32_t cpu; 529 uint32_t pid; 530 uint32_t tid; 531 uint32_t reserved__; /* For alignment */ 532 uint64_t ip; 533 char msg[MAX_AUXTRACE_ERROR_MSG]; 534}; 535 536 PERF_RECORD_HEADER_FEATURE = 80, 537 538Describes a header feature. These are records used in pipe-mode that 539contain information that otherwise would be in perf.data file's header. 540 541 PERF_RECORD_COMPRESSED = 81, 542 543struct compressed_event { 544 struct perf_event_header header; 545 char data[]; 546}; 547 548The header is followed by compressed data frame that can be decompressed 549into array of perf trace records. The size of the entire compressed event 550record including the header is limited by the max value of header.size. 551 552Event types 553 554Define the event attributes with their IDs. 555 556An array bound by the perf_file_section size. 557 558 struct { 559 struct perf_event_attr attr; /* Size defined by header.attr_size */ 560 struct perf_file_section ids; 561 } 562 563ids points to a array of uint64_t defining the ids for event attr attr. 564 565Pipe-mode data 566 567Pipe-mode avoid seeks in the file by removing the perf_file_section and flags 568from the struct perf_header. The trimmed header is: 569 570struct perf_pipe_file_header { 571 u64 magic; 572 u64 size; 573}; 574 575The information about attrs, data, and event_types is instead in the 576synthesized events PERF_RECORD_ATTR, PERF_RECORD_HEADER_TRACING_DATA, 577PERF_RECORD_HEADER_EVENT_TYPE, and PERF_RECORD_HEADER_FEATURE 578that are generated by perf record in pipe-mode. 579 580 581References: 582 583include/uapi/linux/perf_event.h 584 585This is the canonical description of the kernel generated perf_events 586and the perf_event_attrs. 587 588perf_events manpage 589 590A manpage describing perf_event and perf_event_attr is here: 591http://web.eece.maine.edu/~vweaver/projects/perf_events/programming.html 592This tends to be slightly behind the kernel include, but has better 593descriptions. An (typically older) version of the man page may be 594included with the standard Linux man pages, available with "man 595perf_events" 596 597pmu-tools 598 599https://github.com/andikleen/pmu-tools/tree/master/parser 600 601A definition of the perf.data format in python "construct" format is available 602in pmu-tools parser. This allows to read perf.data from python and dump it. 603 604quipper 605 606The quipper C++ parser is available at 607http://github.com/google/perf_data_converter/tree/master/src/quipper 608 609