1perf-record(1) 2============== 3 4NAME 5---- 6perf-record - Run a command and record its profile into perf.data 7 8SYNOPSIS 9-------- 10[verse] 11'perf record' [-e <EVENT> | --event=EVENT] [-a] <command> 12'perf record' [-e <EVENT> | --event=EVENT] [-a] \-- <command> [<options>] 13 14DESCRIPTION 15----------- 16This command runs a command and gathers a performance counter profile 17from it, into perf.data - without displaying anything. 18 19This file can then be inspected later on, using 'perf report'. 20 21 22OPTIONS 23------- 24<command>...:: 25 Any command you can specify in a shell. 26 27-e:: 28--event=:: 29 Select the PMU event. Selection can be: 30 31 - a symbolic event name (use 'perf list' to list all events) 32 33 - a raw PMU event in the form of rN where N is a hexadecimal value 34 that represents the raw register encoding with the layout of the 35 event control registers as described by entries in 36 /sys/bus/event_source/devices/cpu/format/*. 37 38 - a symbolic or raw PMU event followed by an optional colon 39 and a list of event modifiers, e.g., cpu-cycles:p. See the 40 linkperf:perf-list[1] man page for details on event modifiers. 41 42 - a symbolically formed PMU event like 'pmu/param1=0x3,param2/' where 43 'param1', 'param2', etc are defined as formats for the PMU in 44 /sys/bus/event_source/devices/<pmu>/format/*. 45 46 - a symbolically formed event like 'pmu/config=M,config1=N,config3=K/' 47 48 where M, N, K are numbers (in decimal, hex, octal format). Acceptable 49 values for each of 'config', 'config1' and 'config2' are defined by 50 corresponding entries in /sys/bus/event_source/devices/<pmu>/format/* 51 param1 and param2 are defined as formats for the PMU in: 52 /sys/bus/event_source/devices/<pmu>/format/* 53 54 There are also some parameters which are not defined in .../<pmu>/format/*. 55 These params can be used to overload default config values per event. 56 Here are some common parameters: 57 - 'period': Set event sampling period 58 - 'freq': Set event sampling frequency 59 - 'time': Disable/enable time stamping. Acceptable values are 1 for 60 enabling time stamping. 0 for disabling time stamping. 61 The default is 1. 62 - 'call-graph': Disable/enable callgraph. Acceptable str are "fp" for 63 FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and 64 "no" for disable callgraph. 65 - 'stack-size': user stack size for dwarf mode 66 - 'name' : User defined event name. Single quotes (') may be used to 67 escape symbols in the name from parsing by shell and tool 68 like this: name=\'CPU_CLK_UNHALTED.THREAD:cmask=0x1\'. 69 - 'aux-output': Generate AUX records instead of events. This requires 70 that an AUX area event is also provided. 71 - 'aux-sample-size': Set sample size for AUX area sampling. If the 72 '--aux-sample' option has been used, set aux-sample-size=0 to disable 73 AUX area sampling for the event. 74 75 See the linkperf:perf-list[1] man page for more parameters. 76 77 Note: If user explicitly sets options which conflict with the params, 78 the value set by the parameters will be overridden. 79 80 Also not defined in .../<pmu>/format/* are PMU driver specific 81 configuration parameters. Any configuration parameter preceded by 82 the letter '@' is not interpreted in user space and sent down directly 83 to the PMU driver. For example: 84 85 perf record -e some_event/@cfg1,@cfg2=config/ ... 86 87 will see 'cfg1' and 'cfg2=config' pushed to the PMU driver associated 88 with the event for further processing. There is no restriction on 89 what the configuration parameters are, as long as their semantic is 90 understood and supported by the PMU driver. 91 92 - a hardware breakpoint event in the form of '\mem:addr[/len][:access]' 93 where addr is the address in memory you want to break in. 94 Access is the memory access type (read, write, execute) it can 95 be passed as follows: '\mem:addr[:[r][w][x]]'. len is the range, 96 number of bytes from specified addr, which the breakpoint will cover. 97 If you want to profile read-write accesses in 0x1000, just set 98 'mem:0x1000:rw'. 99 If you want to profile write accesses in [0x1000~1008), just set 100 'mem:0x1000/8:w'. 101 102 - a group of events surrounded by a pair of brace ("{event1,event2,...}"). 103 Each event is separated by commas and the group should be quoted to 104 prevent the shell interpretation. You also need to use --group on 105 "perf report" to view group events together. 106 107--filter=<filter>:: 108 Event filter. This option should follow an event selector (-e). 109 If the event is a tracepoint, the filter string will be parsed by 110 the kernel. If the event is a hardware trace PMU (e.g. Intel PT 111 or CoreSight), it'll be processed as an address filter. Otherwise 112 it means a general filter using BPF which can be applied for any 113 kind of event. 114 115 - tracepoint filters 116 117 In the case of tracepoints, multiple '--filter' options are combined 118 using '&&'. 119 120 - address filters 121 122 A hardware trace PMU advertises its ability to accept a number of 123 address filters by specifying a non-zero value in 124 /sys/bus/event_source/devices/<pmu>/nr_addr_filters. 125 126 Address filters have the format: 127 128 filter|start|stop|tracestop <start> [/ <size>] [@<file name>] 129 130 Where: 131 - 'filter': defines a region that will be traced. 132 - 'start': defines an address at which tracing will begin. 133 - 'stop': defines an address at which tracing will stop. 134 - 'tracestop': defines a region in which tracing will stop. 135 136 <file name> is the name of the object file, <start> is the offset to the 137 code to trace in that file, and <size> is the size of the region to 138 trace. 'start' and 'stop' filters need not specify a <size>. 139 140 If no object file is specified then the kernel is assumed, in which case 141 the start address must be a current kernel memory address. 142 143 <start> can also be specified by providing the name of a symbol. If the 144 symbol name is not unique, it can be disambiguated by inserting #n where 145 'n' selects the n'th symbol in address order. Alternately #0, #g or #G 146 select only a global symbol. <size> can also be specified by providing 147 the name of a symbol, in which case the size is calculated to the end 148 of that symbol. For 'filter' and 'tracestop' filters, if <size> is 149 omitted and <start> is a symbol, then the size is calculated to the end 150 of that symbol. 151 152 If <size> is omitted and <start> is '*', then the start and size will 153 be calculated from the first and last symbols, i.e. to trace the whole 154 file. 155 156 If symbol names (or '*') are provided, they must be surrounded by white 157 space. 158 159 The filter passed to the kernel is not necessarily the same as entered. 160 To see the filter that is passed, use the -v option. 161 162 The kernel may not be able to configure a trace region if it is not 163 within a single mapping. MMAP events (or /proc/<pid>/maps) can be 164 examined to determine if that is a possibility. 165 166 Multiple filters can be separated with space or comma. 167 168 - bpf filters 169 170 A BPF filter can access the sample data and make a decision based on the 171 data. Users need to set an appropriate sample type to use the BPF 172 filter. BPF filters need root privilege. 173 174 The sample data field can be specified in lower case letter. Multiple 175 filters can be separated with comma. For example, 176 177 --filter 'period > 1000, cpu == 1' 178 or 179 --filter 'mem_op == load || mem_op == store, mem_lvl > l1' 180 181 The former filter only accept samples with period greater than 1000 AND 182 CPU number is 1. The latter one accepts either load and store memory 183 operations but it should have memory level above the L1. Since the 184 mem_op and mem_lvl fields come from the (memory) data_source, it'd only 185 work with some events which set the data_source field. 186 187 Also user should request to collect that information (with -d option in 188 the above case). Otherwise, the following message will be shown. 189 190 $ sudo perf record -e cycles --filter 'mem_op == load' 191 Error: cycles event does not have PERF_SAMPLE_DATA_SRC 192 Hint: please add -d option to perf record. 193 failed to set filter "BPF" on event cycles with 22 (Invalid argument) 194 195 Essentially the BPF filter expression is: 196 197 <term> <operator> <value> (("," | "||") <term> <operator> <value>)* 198 199 The <term> can be one of: 200 ip, id, tid, pid, cpu, time, addr, period, txn, weight, phys_addr, 201 code_pgsz, data_pgsz, weight1, weight2, weight3, ins_lat, retire_lat, 202 p_stage_cyc, mem_op, mem_lvl, mem_snoop, mem_remote, mem_lock, 203 mem_dtlb, mem_blk, mem_hops, uid, gid 204 205 The <operator> can be one of: 206 ==, !=, >, >=, <, <=, & 207 208 The <value> can be one of: 209 <number> (for any term) 210 na, load, store, pfetch, exec (for mem_op) 211 l1, l2, l3, l4, cxl, io, any_cache, lfb, ram, pmem (for mem_lvl) 212 na, none, hit, miss, hitm, fwd, peer (for mem_snoop) 213 remote (for mem_remote) 214 na, locked (for mem_locked) 215 na, l1_hit, l1_miss, l2_hit, l2_miss, any_hit, any_miss, walk, fault (for mem_dtlb) 216 na, by_data, by_addr (for mem_blk) 217 hops0, hops1, hops2, hops3 (for mem_hops) 218 219--exclude-perf:: 220 Don't record events issued by perf itself. This option should follow 221 an event selector (-e) which selects tracepoint event(s). It adds a 222 filter expression 'common_pid != $PERFPID' to filters. If other 223 '--filter' exists, the new filter expression will be combined with 224 them by '&&'. 225 226-a:: 227--all-cpus:: 228 System-wide collection from all CPUs (default if no target is specified). 229 230-p:: 231--pid=:: 232 Record events on existing process ID (comma separated list). 233 234-t:: 235--tid=:: 236 Record events on existing thread ID (comma separated list). 237 This option also disables inheritance by default. Enable it by adding 238 --inherit. 239 240-u:: 241--uid=:: 242 Record events in threads owned by uid. Name or number. 243 244-r:: 245--realtime=:: 246 Collect data with this RT SCHED_FIFO priority. 247 248--no-buffering:: 249 Collect data without buffering. 250 251-c:: 252--count=:: 253 Event period to sample. 254 255-o:: 256--output=:: 257 Output file name. 258 259-i:: 260--no-inherit:: 261 Child tasks do not inherit counters. 262 263-F:: 264--freq=:: 265 Profile at this frequency. Use 'max' to use the currently maximum 266 allowed frequency, i.e. the value in the kernel.perf_event_max_sample_rate 267 sysctl. Will throttle down to the currently maximum allowed frequency. 268 See --strict-freq. 269 270--strict-freq:: 271 Fail if the specified frequency can't be used. 272 273-m:: 274--mmap-pages=:: 275 Number of mmap data pages (must be a power of two) or size 276 specification in bytes with appended unit character - B/K/M/G. 277 The size is rounded up to the nearest power-of-two page value. 278 By adding a comma, an additional parameter with the same 279 semantics used for the normal mmap areas can be specified for 280 AUX tracing area. 281 282-g:: 283 Enables call-graph (stack chain/backtrace) recording for both 284 kernel space and user space. 285 286--call-graph:: 287 Setup and enable call-graph (stack chain/backtrace) recording, 288 implies -g. Default is "fp" (for user space). 289 290 The unwinding method used for kernel space is dependent on the 291 unwinder used by the active kernel configuration, i.e 292 CONFIG_UNWINDER_FRAME_POINTER (fp) or CONFIG_UNWINDER_ORC (orc) 293 294 Any option specified here controls the method used for user space. 295 296 Valid options are "fp" (frame pointer), "dwarf" (DWARF's CFI - 297 Call Frame Information) or "lbr" (Hardware Last Branch Record 298 facility). 299 300 In some systems, where binaries are build with gcc 301 --fomit-frame-pointer, using the "fp" method will produce bogus 302 call graphs, using "dwarf", if available (perf tools linked to 303 the libunwind or libdw library) should be used instead. 304 Using the "lbr" method doesn't require any compiler options. It 305 will produce call graphs from the hardware LBR registers. The 306 main limitation is that it is only available on new Intel 307 platforms, such as Haswell. It can only get user call chain. It 308 doesn't work with branch stack sampling at the same time. 309 310 When "dwarf" recording is used, perf also records (user) stack dump 311 when sampled. Default size of the stack dump is 8192 (bytes). 312 User can change the size by passing the size after comma like 313 "--call-graph dwarf,4096". 314 315 When "fp" recording is used, perf tries to save stack entries 316 up to the number specified in sysctl.kernel.perf_event_max_stack 317 by default. User can change the number by passing it after comma 318 like "--call-graph fp,32". 319 320-q:: 321--quiet:: 322 Don't print any warnings or messages, useful for scripting. 323 324-v:: 325--verbose:: 326 Be more verbose (show counter open errors, etc). 327 328-s:: 329--stat:: 330 Record per-thread event counts. Use it with 'perf report -T' to see 331 the values. 332 333-d:: 334--data:: 335 Record the sample virtual addresses. 336 337--phys-data:: 338 Record the sample physical addresses. 339 340--data-page-size:: 341 Record the sampled data address data page size. 342 343--code-page-size:: 344 Record the sampled code address (ip) page size 345 346-T:: 347--timestamp:: 348 Record the sample timestamps. Use it with 'perf report -D' to see the 349 timestamps, for instance. 350 351-P:: 352--period:: 353 Record the sample period. 354 355--sample-cpu:: 356 Record the sample cpu. 357 358--sample-identifier:: 359 Record the sample identifier i.e. PERF_SAMPLE_IDENTIFIER bit set in 360 the sample_type member of the struct perf_event_attr argument to the 361 perf_event_open system call. 362 363-n:: 364--no-samples:: 365 Don't sample. 366 367-R:: 368--raw-samples:: 369Collect raw sample records from all opened counters (default for tracepoint counters). 370 371-C:: 372--cpu:: 373Collect samples only on the list of CPUs provided. Multiple CPUs can be provided as a 374comma-separated list with no space: 0,1. Ranges of CPUs are specified with -: 0-2. 375In per-thread mode with inheritance mode on (default), samples are captured only when 376the thread executes on the designated CPUs. Default is to monitor all CPUs. 377 378User space tasks can migrate between CPUs, so when tracing selected CPUs, 379a dummy event is created to track sideband for all CPUs. 380 381-B:: 382--no-buildid:: 383Do not save the build ids of binaries in the perf.data files. This skips 384post processing after recording, which sometimes makes the final step in 385the recording process to take a long time, as it needs to process all 386events looking for mmap records. The downside is that it can misresolve 387symbols if the workload binaries used when recording get locally rebuilt 388or upgraded, because the only key available in this case is the 389pathname. You can also set the "record.build-id" config variable to 390'skip to have this behaviour permanently. 391 392-N:: 393--no-buildid-cache:: 394Do not update the buildid cache. This saves some overhead in situations 395where the information in the perf.data file (which includes buildids) 396is sufficient. You can also set the "record.build-id" config variable to 397'no-cache' to have the same effect. 398 399-G name,...:: 400--cgroup name,...:: 401monitor only in the container (cgroup) called "name". This option is available only 402in per-cpu mode. The cgroup filesystem must be mounted. All threads belonging to 403container "name" are monitored when they run on the monitored CPUs. Multiple cgroups 404can be provided. Each cgroup is applied to the corresponding event, i.e., first cgroup 405to first event, second cgroup to second event and so on. It is possible to provide 406an empty cgroup (monitor all the time) using, e.g., -G foo,,bar. Cgroups must have 407corresponding events, i.e., they always refer to events defined earlier on the command 408line. If the user wants to track multiple events for a specific cgroup, the user can 409use '-e e1 -e e2 -G foo,foo' or just use '-e e1 -e e2 -G foo'. 410 411If wanting to monitor, say, 'cycles' for a cgroup and also for system wide, this 412command line can be used: 'perf stat -e cycles -G cgroup_name -a -e cycles'. 413 414-b:: 415--branch-any:: 416Enable taken branch stack sampling. Any type of taken branch may be sampled. 417This is a shortcut for --branch-filter any. See --branch-filter for more infos. 418 419-j:: 420--branch-filter:: 421Enable taken branch stack sampling. Each sample captures a series of consecutive 422taken branches. The number of branches captured with each sample depends on the 423underlying hardware, the type of branches of interest, and the executed code. 424It is possible to select the types of branches captured by enabling filters. The 425following filters are defined: 426 427 - any: any type of branches 428 - any_call: any function call or system call 429 - any_ret: any function return or system call return 430 - ind_call: any indirect branch 431 - ind_jmp: any indirect jump 432 - call: direct calls, including far (to/from kernel) calls 433 - u: only when the branch target is at the user level 434 - k: only when the branch target is in the kernel 435 - hv: only when the target is at the hypervisor level 436 - in_tx: only when the target is in a hardware transaction 437 - no_tx: only when the target is not in a hardware transaction 438 - abort_tx: only when the target is a hardware transaction abort 439 - cond: conditional branches 440 - call_stack: save call stack 441 - no_flags: don't save branch flags e.g prediction, misprediction etc 442 - no_cycles: don't save branch cycles 443 - hw_index: save branch hardware index 444 - save_type: save branch type during sampling in case binary is not available later 445 For the platforms with Intel Arch LBR support (12th-Gen+ client or 446 4th-Gen Xeon+ server), the save branch type is unconditionally enabled 447 when the taken branch stack sampling is enabled. 448 - priv: save privilege state during sampling in case binary is not available later 449 - counter: save occurrences of the event since the last branch entry. Currently, the 450 feature is only supported by a newer CPU, e.g., Intel Sierra Forest and 451 later platforms. An error out is expected if it's used on the unsupported 452 kernel or CPUs. 453 454+ 455The option requires at least one branch type among any, any_call, any_ret, ind_call, cond. 456The privilege levels may be omitted, in which case, the privilege levels of the associated 457event are applied to the branch filter. Both kernel (k) and hypervisor (hv) privilege 458levels are subject to permissions. When sampling on multiple events, branch stack sampling 459is enabled for all the sampling events. The sampled branch type is the same for all events. 460The various filters must be specified as a comma separated list: --branch-filter any_ret,u,k 461Note that this feature may not be available on all processors. 462 463-W:: 464--weight:: 465Enable weightened sampling. An additional weight is recorded per sample and can be 466displayed with the weight and local_weight sort keys. This currently works for TSX 467abort events and some memory events in precise mode on modern Intel CPUs. 468 469--namespaces:: 470Record events of type PERF_RECORD_NAMESPACES. This enables 'cgroup_id' sort key. 471 472--all-cgroups:: 473Record events of type PERF_RECORD_CGROUP. This enables 'cgroup' sort key. 474 475--transaction:: 476Record transaction flags for transaction related events. 477 478--per-thread:: 479Use per-thread mmaps. By default per-cpu mmaps are created. This option 480overrides that and uses per-thread mmaps. A side-effect of that is that 481inheritance is automatically disabled. --per-thread is ignored with a warning 482if combined with -a or -C options. 483 484-D:: 485--delay=:: 486After starting the program, wait msecs before measuring (-1: start with events 487disabled), or enable events only for specified ranges of msecs (e.g. 488-D 10-20,30-40 means wait 10 msecs, enable for 10 msecs, wait 10 msecs, enable 489for 10 msecs, then stop). Note, delaying enabling of events is useful to filter 490out the startup phase of the program, which is often very different. 491 492-I:: 493--intr-regs:: 494Capture machine state (registers) at interrupt, i.e., on counter overflows for 495each sample. List of captured registers depends on the architecture. This option 496is off by default. It is possible to select the registers to sample using their 497symbolic names, e.g. on x86, ax, si. To list the available registers use 498--intr-regs=\?. To name registers, pass a comma separated list such as 499--intr-regs=ax,bx. The list of register is architecture dependent. 500 501--user-regs:: 502Similar to -I, but capture user registers at sample time. To list the available 503user registers use --user-regs=\?. 504 505--running-time:: 506Record running and enabled time for read events (:S) 507 508-k:: 509--clockid:: 510Sets the clock id to use for the various time fields in the perf_event_type 511records. See clock_gettime(). In particular CLOCK_MONOTONIC and 512CLOCK_MONOTONIC_RAW are supported, some events might also allow 513CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI. 514 515-S:: 516--snapshot:: 517Select AUX area tracing Snapshot Mode. This option is valid only with an 518AUX area tracing event. Optionally, certain snapshot capturing parameters 519can be specified in a string that follows this option: 520 521 - 'e': take one last snapshot on exit; guarantees that there is at least one 522 snapshot in the output file; 523 - <size>: if the PMU supports this, specify the desired snapshot size. 524 525In Snapshot Mode trace data is captured only when signal SIGUSR2 is received 526and on exit if the above 'e' option is given. 527 528--aux-sample[=OPTIONS]:: 529Select AUX area sampling. At least one of the events selected by the -e option 530must be an AUX area event. Samples on other events will be created containing 531data from the AUX area. Optionally sample size may be specified, otherwise it 532defaults to 4KiB. 533 534--proc-map-timeout:: 535When processing pre-existing threads /proc/XXX/mmap, it may take a long time, 536because the file may be huge. A time out is needed in such cases. 537This option sets the time out limit. The default value is 500 ms. 538 539--switch-events:: 540Record context switch events i.e. events of type PERF_RECORD_SWITCH or 541PERF_RECORD_SWITCH_CPU_WIDE. In some cases (e.g. Intel PT, CoreSight or Arm SPE) 542switch events will be enabled automatically, which can be suppressed by 543by the option --no-switch-events. 544 545--vmlinux=PATH:: 546Specify vmlinux path which has debuginfo. 547(enabled when BPF prologue is on) 548 549--buildid-all:: 550Record build-id of all DSOs regardless whether it's actually hit or not. 551 552--buildid-mmap:: 553Record build ids in mmap2 events, disables build id cache (implies --no-buildid). 554 555--aio[=n]:: 556Use <n> control blocks in asynchronous (Posix AIO) trace writing mode (default: 1, max: 4). 557Asynchronous mode is supported only when linking Perf tool with libc library 558providing implementation for Posix AIO API. 559 560--affinity=mode:: 561Set affinity mask of trace reading thread according to the policy defined by 'mode' value: 562 563 - node - thread affinity mask is set to NUMA node cpu mask of the processed mmap buffer 564 - cpu - thread affinity mask is set to cpu of the processed mmap buffer 565 566--mmap-flush=number:: 567 568Specify minimal number of bytes that is extracted from mmap data pages and 569processed for output. One can specify the number using B/K/M/G suffixes. 570 571The maximal allowed value is a quarter of the size of mmaped data pages. 572 573The default option value is 1 byte which means that every time that the output 574writing thread finds some new data in the mmaped buffer the data is extracted, 575possibly compressed (-z) and written to the output, perf.data or pipe. 576 577Larger data chunks are compressed more effectively in comparison to smaller 578chunks so extraction of larger chunks from the mmap data pages is preferable 579from the perspective of output size reduction. 580 581Also at some cases executing less output write syscalls with bigger data size 582can take less time than executing more output write syscalls with smaller data 583size thus lowering runtime profiling overhead. 584 585-z:: 586--compression-level[=n]:: 587Produce compressed trace using specified level n (default: 1 - fastest compression, 58822 - smallest trace) 589 590--all-kernel:: 591Configure all used events to run in kernel space. 592 593--all-user:: 594Configure all used events to run in user space. 595 596--kernel-callchains:: 597Collect callchains only from kernel space. I.e. this option sets 598perf_event_attr.exclude_callchain_user to 1. 599 600--user-callchains:: 601Collect callchains only from user space. I.e. this option sets 602perf_event_attr.exclude_callchain_kernel to 1. 603 604Don't use both --kernel-callchains and --user-callchains at the same time or no 605callchains will be collected. 606 607--timestamp-filename 608Append timestamp to output file name. 609 610--timestamp-boundary:: 611Record timestamp boundary (time of first/last samples). 612 613--switch-output[=mode]:: 614Generate multiple perf.data files, timestamp prefixed, switching to a new one 615based on 'mode' value: 616 617 - "signal" - when receiving a SIGUSR2 (default value) or 618 - <size> - when reaching the size threshold, size is expected to 619 be a number with appended unit character - B/K/M/G 620 - <time> - when reaching the time threshold, size is expected to 621 be a number with appended unit character - s/m/h/d 622 623 Note: the precision of the size threshold hugely depends 624 on your configuration - the number and size of your ring 625 buffers (-m). It is generally more precise for higher sizes 626 (like >5M), for lower values expect different sizes. 627 628A possible use case is to, given an external event, slice the perf.data file 629that gets then processed, possibly via a perf script, to decide if that 630particular perf.data snapshot should be kept or not. 631 632Implies --timestamp-filename, --no-buildid and --no-buildid-cache. 633The reason for the latter two is to reduce the data file switching 634overhead. You can still switch them on with: 635 636 --switch-output --no-no-buildid --no-no-buildid-cache 637 638--switch-output-event:: 639Events that will cause the switch of the perf.data file, auto-selecting 640--switch-output=signal, the results are similar as internally the side band 641thread will also send a SIGUSR2 to the main one. 642 643Uses the same syntax as --event, it will just not be recorded, serving only to 644switch the perf.data file as soon as the --switch-output event is processed by 645a separate sideband thread. 646 647This sideband thread is also used to other purposes, like processing the 648PERF_RECORD_BPF_EVENT records as they happen, asking the kernel for extra BPF 649information, etc. 650 651--switch-max-files=N:: 652 653When rotating perf.data with --switch-output, only keep N files. 654 655--dry-run:: 656Parse options then exit. --dry-run can be used to detect errors in cmdline 657options. 658 659'perf record --dry-run -e' can act as a BPF script compiler if llvm.dump-obj 660in config file is set to true. 661 662--synth=TYPE:: 663Collect and synthesize given type of events (comma separated). Note that 664this option controls the synthesis from the /proc filesystem which represent 665task status for pre-existing threads. 666 667Kernel (and some other) events are recorded regardless of the 668choice in this option. For example, --synth=no would have MMAP events for 669kernel and modules. 670 671Available types are: 672 673 - 'task' - synthesize FORK and COMM events for each task 674 - 'mmap' - synthesize MMAP events for each process (implies 'task') 675 - 'cgroup' - synthesize CGROUP events for each cgroup 676 - 'all' - synthesize all events (default) 677 - 'no' - do not synthesize any of the above events 678 679--tail-synthesize:: 680Instead of collecting non-sample events (for example, fork, comm, mmap) at 681the beginning of record, collect them during finalizing an output file. 682The collected non-sample events reflects the status of the system when 683record is finished. 684 685--overwrite:: 686Makes all events use an overwritable ring buffer. An overwritable ring 687buffer works like a flight recorder: when it gets full, the kernel will 688overwrite the oldest records, that thus will never make it to the 689perf.data file. 690 691When '--overwrite' and '--switch-output' are used perf records and drops 692events until it receives a signal, meaning that something unusual was 693detected that warrants taking a snapshot of the most current events, 694those fitting in the ring buffer at that moment. 695 696'overwrite' attribute can also be set or canceled for an event using 697config terms. For example: 'cycles/overwrite/' and 'instructions/no-overwrite/'. 698 699Implies --tail-synthesize. 700 701--kcore:: 702Make a copy of /proc/kcore and place it into a directory with the perf data file. 703 704--max-size=<size>:: 705Limit the sample data max size, <size> is expected to be a number with 706appended unit character - B/K/M/G 707 708--num-thread-synthesize:: 709 The number of threads to run when synthesizing events for existing processes. 710 By default, the number of threads equals 1. 711 712ifdef::HAVE_LIBPFM[] 713--pfm-events events:: 714Select a PMU event using libpfm4 syntax (see http://perfmon2.sf.net) 715including support for event filters. For example '--pfm-events 716inst_retired:any_p:u:c=1:i'. More than one event can be passed to the 717option using the comma separator. Hardware events and generic hardware 718events cannot be mixed together. The latter must be used with the -e 719option. The -e option and this one can be mixed and matched. Events 720can be grouped using the {} notation. 721endif::HAVE_LIBPFM[] 722 723--control=fifo:ctl-fifo[,ack-fifo]:: 724--control=fd:ctl-fd[,ack-fd]:: 725ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows. 726Listen on ctl-fd descriptor for command to control measurement. 727 728Available commands: 729 730 - 'enable' : enable events 731 - 'disable' : disable events 732 - 'enable name' : enable event 'name' 733 - 'disable name' : disable event 'name' 734 - 'snapshot' : AUX area tracing snapshot). 735 - 'stop' : stop perf record 736 - 'ping' : ping 737 - 'evlist [-v|-g|-F] : display all events 738 739 -F Show just the sample frequency used for each event. 740 -v Show all fields. 741 -g Show event group information. 742 743Measurements can be started with events disabled using --delay=-1 option. Optionally 744send control command completion ('ack\n') to ack-fd descriptor to synchronize with the 745controlling process. Example of bash shell script to enable and disable events during 746measurements: 747 748 #!/bin/bash 749 750 ctl_dir=/tmp/ 751 752 ctl_fifo=${ctl_dir}perf_ctl.fifo 753 test -p ${ctl_fifo} && unlink ${ctl_fifo} 754 mkfifo ${ctl_fifo} 755 exec {ctl_fd}<>${ctl_fifo} 756 757 ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo 758 test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo} 759 mkfifo ${ctl_ack_fifo} 760 exec {ctl_fd_ack}<>${ctl_ack_fifo} 761 762 perf record -D -1 -e cpu-cycles -a \ 763 --control fd:${ctl_fd},${ctl_fd_ack} \ 764 -- sleep 30 & 765 perf_pid=$! 766 767 sleep 5 && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})" 768 sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})" 769 770 exec {ctl_fd_ack}>&- 771 unlink ${ctl_ack_fifo} 772 773 exec {ctl_fd}>&- 774 unlink ${ctl_fifo} 775 776 wait -n ${perf_pid} 777 exit $? 778 779--threads=<spec>:: 780Write collected trace data into several data files using parallel threads. 781<spec> value can be user defined list of masks. Masks separated by colon 782define CPUs to be monitored by a thread and affinity mask of that thread 783is separated by slash: 784 785 <cpus mask 1>/<affinity mask 1>:<cpus mask 2>/<affinity mask 2>:... 786 787CPUs or affinity masks must not overlap with other corresponding masks. 788Invalid CPUs are ignored, but masks containing only invalid CPUs are not 789allowed. 790 791For example user specification like the following: 792 793 0,2-4/2-4:1,5-7/5-7 794 795specifies parallel threads layout that consists of two threads, 796the first thread monitors CPUs 0 and 2-4 with the affinity mask 2-4, 797the second monitors CPUs 1 and 5-7 with the affinity mask 5-7. 798 799<spec> value can also be a string meaning predefined parallel threads 800layout: 801 802 - cpu - create new data streaming thread for every monitored cpu 803 - core - create new thread to monitor CPUs grouped by a core 804 - package - create new thread to monitor CPUs grouped by a package 805 - numa - create new threed to monitor CPUs grouped by a NUMA domain 806 807Predefined layouts can be used on systems with large number of CPUs in 808order not to spawn multiple per-cpu streaming threads but still avoid LOST 809events in data directory files. Option specified with no or empty value 810defaults to CPU layout. Masks defined or provided by the option value are 811filtered through the mask provided by -C option. 812 813--debuginfod[=URLs]:: 814 Specify debuginfod URL to be used when cacheing perf.data binaries, 815 it follows the same syntax as the DEBUGINFOD_URLS variable, like: 816 817 http://192.168.122.174:8002 818 819 If the URLs is not specified, the value of DEBUGINFOD_URLS 820 system environment variable is used. 821 822--off-cpu:: 823 Enable off-cpu profiling with BPF. The BPF program will collect 824 task scheduling information with (user) stacktrace and save them 825 as sample data of a software event named "offcpu-time". The 826 sample period will have the time the task slept in nanoseconds. 827 828 Note that BPF can collect stack traces using frame pointer ("fp") 829 only, as of now. So the applications built without the frame 830 pointer might see bogus addresses. 831 832--setup-filter=<action>:: 833 Prepare BPF filter to be used by regular users. The action should be 834 either "pin" or "unpin". The filter can be used after it's pinned. 835 836 837include::intel-hybrid.txt[] 838 839SEE ALSO 840-------- 841linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-intel-pt[1] 842