diff options
Diffstat (limited to 'tools/perf/Documentation/perf-intel-pt.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-intel-pt.txt | 612 |
1 files changed, 386 insertions, 226 deletions
diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt index 4c90cc176f81..cc0f37f0fa5a 100644 --- a/tools/perf/Documentation/perf-intel-pt.txt +++ b/tools/perf/Documentation/perf-intel-pt.txt @@ -115,9 +115,13 @@ toggle respectively. perf script also supports higher level ways to dump instruction traces: + perf script --insn-trace=disasm + +or to use the xed disassembler, which requires installing the xed tool +(see XED below): + perf script --insn-trace --xed -Dump all instructions. This requires installing the xed tool (see XED below) Dumping all instructions in a long trace can be fairly slow. It is usually better to start with higher level decoding, like @@ -130,12 +134,12 @@ or and then select a time range of interest. The time range can then be examined in detail with - perf script --time starttime,stoptime --insn-trace --xed + perf script --time starttime,stoptime --insn-trace=disasm While examining the trace it's also useful to filter on specific CPUs using the -C option - perf script --time starttime,stoptime --insn-trace --xed -C 1 + perf script --time starttime,stoptime --insn-trace=disasm -C 1 Dump all instructions in time range on CPU 1. @@ -147,7 +151,7 @@ displayed as follows: There are two ways that instructions-per-cycle (IPC) can be calculated depending on the recording. -If the 'cyc' config term (see config terms section below) was used, then IPC +If the 'cyc' config term (see <<_config_terms,config terms>> section below) was used, then IPC and cycle events are calculated using the cycle count from CYC packets, otherwise MTC packets are used - refer to the 'mtc' config term. When MTC is used, however, the values are less accurate because the timing is less accurate. @@ -235,7 +239,7 @@ which is the same as -e intel_pt/tsc=1,noretcomp=0/ -Note there are now new config terms - see section 'config terms' further below. +Note there are other config terms - see section <<_config_terms,config terms>> further below. The config terms are listed in /sys/devices/intel_pt/format. They are bit fields within the config member of the struct perf_event_attr which is @@ -307,218 +311,271 @@ perf_event_attr is displayed if the -vv option is used e.g. config terms ~~~~~~~~~~~~ -The June 2015 version of Intel 64 and IA-32 Architectures Software Developer -Manuals, Chapter 36 Intel Processor Trace, defined new Intel PT features. -Some of the features are reflect in new config terms. All the config terms are -described below. - -tsc Always supported. Produces TSC timestamp packets to provide - timing information. In some cases it is possible to decode - without timing information, for example a per-thread context - that does not overlap executable memory maps. - - The default config selects tsc (i.e. tsc=1). - -noretcomp Always supported. Disables "return compression" so a TIP packet - is produced when a function returns. Causes more packets to be - produced but might make decoding more reliable. - - The default config does not select noretcomp (i.e. noretcomp=0). - -psb_period Allows the frequency of PSB packets to be specified. - - The PSB packet is a synchronization packet that provides a - starting point for decoding or recovery from errors. - - Support for psb_period is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/psb_cyc - - which contains "1" if the feature is supported and "0" - otherwise. - - Valid values are given by: - - /sys/bus/event_source/devices/intel_pt/caps/psb_periods - - which contains a hexadecimal value, the bits of which represent - valid values e.g. bit 2 set means value 2 is valid. - - The psb_period value is converted to the approximate number of - trace bytes between PSB packets as: - - 2 ^ (value + 11) - - e.g. value 3 means 16KiB bytes between PSBs - - If an invalid value is entered, the error message - will give a list of valid values e.g. - - $ perf record -e intel_pt/psb_period=15/u uname - Invalid psb_period for intel_pt. Valid values are: 0-5 - - If MTC packets are selected, the default config selects a value - of 3 (i.e. psb_period=3) or the nearest lower value that is - supported (0 is always supported). Otherwise the default is 0. - - If decoding is expected to be reliable and the buffer is large - then a large PSB period can be used. - - Because a TSC packet is produced with PSB, the PSB period can - also affect the granularity to timing information in the absence - of MTC or CYC. - -mtc Produces MTC timing packets. - - MTC packets provide finer grain timestamp information than TSC - packets. MTC packets record time using the hardware crystal - clock (CTC) which is related to TSC packets using a TMA packet. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/mtc - - which contains "1" if the feature is supported and - "0" otherwise. - - The frequency of MTC packets can also be specified - see - mtc_period below. - -mtc_period Specifies how frequently MTC packets are produced - see mtc - above for how to determine if MTC packets are supported. - - Valid values are given by: - - /sys/bus/event_source/devices/intel_pt/caps/mtc_periods - - which contains a hexadecimal value, the bits of which represent - valid values e.g. bit 2 set means value 2 is valid. - - The mtc_period value is converted to the MTC frequency as: - - CTC-frequency / (2 ^ value) - - e.g. value 3 means one eighth of CTC-frequency - - Where CTC is the hardware crystal clock, the frequency of which - can be related to TSC via values provided in cpuid leaf 0x15. - - If an invalid value is entered, the error message - will give a list of valid values e.g. - - $ perf record -e intel_pt/mtc_period=15/u uname - Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9 - - The default value is 3 or the nearest lower value - that is supported (0 is always supported). - -cyc Produces CYC timing packets. - - CYC packets provide even finer grain timestamp information than - MTC and TSC packets. A CYC packet contains the number of CPU - cycles since the last CYC packet. Unlike MTC and TSC packets, - CYC packets are only sent when another packet is also sent. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/psb_cyc - - which contains "1" if the feature is supported and - "0" otherwise. - - The number of CYC packets produced can be reduced by specifying - a threshold - see cyc_thresh below. - -cyc_thresh Specifies how frequently CYC packets are produced - see cyc - above for how to determine if CYC packets are supported. - - Valid cyc_thresh values are given by: - - /sys/bus/event_source/devices/intel_pt/caps/cycle_thresholds - - which contains a hexadecimal value, the bits of which represent - valid values e.g. bit 2 set means value 2 is valid. - - The cyc_thresh value represents the minimum number of CPU cycles - that must have passed before a CYC packet can be sent. The - number of CPU cycles is: - - 2 ^ (value - 1) - - e.g. value 4 means 8 CPU cycles must pass before a CYC packet - can be sent. Note a CYC packet is still only sent when another - packet is sent, not at, e.g. every 8 CPU cycles. - - If an invalid value is entered, the error message - will give a list of valid values e.g. - - $ perf record -e intel_pt/cyc,cyc_thresh=15/u uname - Invalid cyc_thresh for intel_pt. Valid values are: 0-12 - - CYC packets are not requested by default. - -pt Specifies pass-through which enables the 'branch' config term. - - The default config selects 'pt' if it is available, so a user will - never need to specify this term. - -branch Enable branch tracing. Branch tracing is enabled by default so to - disable branch tracing use 'branch=0'. - - The default config selects 'branch' if it is available. - -ptw Enable PTWRITE packets which are produced when a ptwrite instruction - is executed. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/ptwrite - - which contains "1" if the feature is supported and - "0" otherwise. - - As an alternative, refer to "Emulated PTWRITE" further below. - -fup_on_ptw Enable a FUP packet to follow the PTWRITE packet. The FUP packet - provides the address of the ptwrite instruction. In the absence of - fup_on_ptw, the decoder will use the address of the previous branch - if branch tracing is enabled, otherwise the address will be zero. - Note that fup_on_ptw will work even when branch tracing is disabled. - -pwr_evt Enable power events. The power events provide information about - changes to the CPU C-state. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/power_event_trace - - which contains "1" if the feature is supported and - "0" otherwise. - -event Enable Event Trace. The events provide information about asynchronous - events. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/event_trace - - which contains "1" if the feature is supported and - "0" otherwise. - -notnt Disable TNT packets. Without TNT packets, it is not possible to walk - executable code to reconstruct control flow, however FUP, TIP, TIP.PGE - and TIP.PGD packets still indicate asynchronous control flow, and (if - return compression is disabled - see noretcomp) return statements. - The advantage of eliminating TNT packets is reducing the size of the - trace and corresponding tracing overhead. - - Support for this feature is indicated by: - - /sys/bus/event_source/devices/intel_pt/caps/tnt_disable - - which contains "1" if the feature is supported and - "0" otherwise. - +Config terms are parameters specified with the -e intel_pt// event option, +for example: + + -e intel_pt/cyc/ + +which selects cycle accurate mode. Each config term can have a value which +defaults to 1, so the above is the same as: + + -e intel_pt/cyc=1/ + +Some terms are set by default, so must be set to 0 to turn them off. For +example, to turn off branch tracing: + + -e intel_pt/branch=0/ + +Multiple config terms are separated by commas, for example: + + -e intel_pt/cyc,mtc_period=9/ + +There are also common config terms, see linkperf:perf-record[1] documentation. + +Intel PT config terms are described below. + +*tsc*:: +Always supported. Produces TSC timestamp packets to provide +timing information. In some cases it is possible to decode +without timing information, for example a per-thread context +that does not overlap executable memory maps. ++ +The default config selects tsc (i.e. tsc=1). + +*noretcomp*:: +Always supported. Disables "return compression" so a TIP packet +is produced when a function returns. Causes more packets to be +produced but might make decoding more reliable. ++ +The default config does not select noretcomp (i.e. noretcomp=0). + +*psb_period*:: +Allows the frequency of PSB packets to be specified. ++ +The PSB packet is a synchronization packet that provides a +starting point for decoding or recovery from errors. ++ +Support for psb_period is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/psb_cyc ++ +which contains "1" if the feature is supported and "0" +otherwise. ++ +Valid values are given by: ++ + /sys/bus/event_source/devices/intel_pt/caps/psb_periods ++ +which contains a hexadecimal value, the bits of which represent +valid values e.g. bit 2 set means value 2 is valid. ++ +The psb_period value is converted to the approximate number of +trace bytes between PSB packets as: ++ + 2 ^ (value + 11) ++ +e.g. value 3 means 16KiB bytes between PSBs ++ +If an invalid value is entered, the error message +will give a list of valid values e.g. ++ + $ perf record -e intel_pt/psb_period=15/u uname + Invalid psb_period for intel_pt. Valid values are: 0-5 ++ +If MTC packets are selected, the default config selects a value +of 3 (i.e. psb_period=3) or the nearest lower value that is +supported (0 is always supported). Otherwise the default is 0. ++ +If decoding is expected to be reliable and the buffer is large +then a large PSB period can be used. ++ +Because a TSC packet is produced with PSB, the PSB period can +also affect the granularity to timing information in the absence +of MTC or CYC. + +*mtc*:: +Produces MTC timing packets. ++ +MTC packets provide finer grain timestamp information than TSC +packets. MTC packets record time using the hardware crystal +clock (CTC) which is related to TSC packets using a TMA packet. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/mtc ++ +which contains "1" if the feature is supported and +"0" otherwise. ++ +The frequency of MTC packets can also be specified - see +mtc_period below. + +*mtc_period*:: +Specifies how frequently MTC packets are produced - see mtc +above for how to determine if MTC packets are supported. ++ +Valid values are given by: ++ + /sys/bus/event_source/devices/intel_pt/caps/mtc_periods ++ +which contains a hexadecimal value, the bits of which represent +valid values e.g. bit 2 set means value 2 is valid. ++ +The mtc_period value is converted to the MTC frequency as: + + CTC-frequency / (2 ^ value) ++ +e.g. value 3 means one eighth of CTC-frequency ++ +Where CTC is the hardware crystal clock, the frequency of which +can be related to TSC via values provided in cpuid leaf 0x15. ++ +If an invalid value is entered, the error message +will give a list of valid values e.g. ++ + $ perf record -e intel_pt/mtc_period=15/u uname + Invalid mtc_period for intel_pt. Valid values are: 0,3,6,9 ++ +The default value is 3 or the nearest lower value +that is supported (0 is always supported). + +*cyc*:: +Produces CYC timing packets. ++ +CYC packets provide even finer grain timestamp information than +MTC and TSC packets. A CYC packet contains the number of CPU +cycles since the last CYC packet. Unlike MTC and TSC packets, +CYC packets are only sent when another packet is also sent. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/psb_cyc ++ +which contains "1" if the feature is supported and +"0" otherwise. ++ +The number of CYC packets produced can be reduced by specifying +a threshold - see cyc_thresh below. + +*cyc_thresh*:: +Specifies how frequently CYC packets are produced - see cyc +above for how to determine if CYC packets are supported. ++ +Valid cyc_thresh values are given by: ++ + /sys/bus/event_source/devices/intel_pt/caps/cycle_thresholds ++ +which contains a hexadecimal value, the bits of which represent +valid values e.g. bit 2 set means value 2 is valid. ++ +The cyc_thresh value represents the minimum number of CPU cycles +that must have passed before a CYC packet can be sent. The +number of CPU cycles is: ++ + 2 ^ (value - 1) ++ +e.g. value 4 means 8 CPU cycles must pass before a CYC packet +can be sent. Note a CYC packet is still only sent when another +packet is sent, not at, e.g. every 8 CPU cycles. ++ +If an invalid value is entered, the error message +will give a list of valid values e.g. ++ + $ perf record -e intel_pt/cyc,cyc_thresh=15/u uname + Invalid cyc_thresh for intel_pt. Valid values are: 0-12 ++ +CYC packets are not requested by default. + +*pt*:: +Specifies pass-through which enables the 'branch' config term. ++ +The default config selects 'pt' if it is available, so a user will +never need to specify this term. + +*branch*:: +Enable branch tracing. Branch tracing is enabled by default so to +disable branch tracing use 'branch=0'. ++ +The default config selects 'branch' if it is available. + +*ptw*:: +Enable PTWRITE packets which are produced when a ptwrite instruction +is executed. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/ptwrite ++ +which contains "1" if the feature is supported and +"0" otherwise. ++ +As an alternative, refer to "Emulated PTWRITE" further below. + +*fup_on_ptw*:: +Enable a FUP packet to follow the PTWRITE packet. The FUP packet +provides the address of the ptwrite instruction. In the absence of +fup_on_ptw, the decoder will use the address of the previous branch +if branch tracing is enabled, otherwise the address will be zero. +Note that fup_on_ptw will work even when branch tracing is disabled. + +*pwr_evt*:: +Enable power events. The power events provide information about +changes to the CPU C-state. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/power_event_trace ++ +which contains "1" if the feature is supported and +"0" otherwise. + +*event*:: +Enable Event Trace. The events provide information about asynchronous +events. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/event_trace ++ +which contains "1" if the feature is supported and +"0" otherwise. + +*notnt*:: +Disable TNT packets. Without TNT packets, it is not possible to walk +executable code to reconstruct control flow, however FUP, TIP, TIP.PGE +and TIP.PGD packets still indicate asynchronous control flow, and (if +return compression is disabled - see noretcomp) return statements. +The advantage of eliminating TNT packets is reducing the size of the +trace and corresponding tracing overhead. ++ +Support for this feature is indicated by: ++ + /sys/bus/event_source/devices/intel_pt/caps/tnt_disable ++ +which contains "1" if the feature is supported and +"0" otherwise. + +*aux-action=start-paused*:: +Start tracing paused, refer to the section <<_pause_or_resume_tracing,Pause or Resume Tracing>> + + +config terms on other events +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Some Intel PT features work with other events, features such as AUX area sampling +and PEBS-via-PT. In those cases, the other events can have config terms below: + +*aux-sample-size*:: + Used to set the AUX area sample size, refer to the section + <<_aux_area_sampling_option,AUX area sampling option>> + +*aux-output*:: + Used to select PEBS-via-PT, refer to the + section <<_pebs_via_intel_pt,PEBS via Intel PT>> + +*aux-action*:: + Used to pause or resume tracing, refer to the section + <<_pause_or_resume_tracing,Pause or Resume Tracing>> AUX area sampling option ~~~~~~~~~~~~~~~~~~~~~~~~ @@ -592,7 +649,8 @@ The default snapshot size is the auxtrace mmap size. If neither auxtrace mmap s nor snapshot size is specified, then the default is 4MiB for privileged users (or if /proc/sys/kernel/perf_event_paranoid < 0), 128KiB for unprivileged users. If an unprivileged user does not specify mmap pages, the mmap pages will be -reduced as described in the 'new auxtrace mmap size option' section below. +reduced as described in the <<_new_auxtrace_mmap_size_option,new auxtrace mmap size option>> +section below. The snapshot size is displayed if the option -vv is used e.g. @@ -683,7 +741,7 @@ Buffer handling ~~~~~~~~~~~~~~~ There may be buffer limitations (i.e. single ToPa entry) which means that actual -buffer sizes are limited to powers of 2 up to 4MiB (MAX_ORDER). In order to +buffer sizes are limited to powers of 2 up to 4MiB (MAX_PAGE_ORDER). In order to provide other sizes, and in particular an arbitrarily large size, multiple buffers are logically concatenated. However an interrupt must be used to switch between buffers. That has two potential problems: @@ -948,11 +1006,11 @@ transaction start, commit or abort. Note that "instructions", "cycles", "branches" and "transactions" events depend on code flow packets which can be disabled by using the config term -"branch=0". Refer to the config terms section above. +"branch=0". Refer to the <<_config_terms,config terms>> section above. "ptwrite" events record the payload of the ptwrite instruction and whether "fup_on_ptw" was used. "ptwrite" events depend on PTWRITE packets which are -recorded only if the "ptw" config term was used. Refer to the config terms +recorded only if the "ptw" config term was used. Refer to the <<_config_terms,config terms>> section above. perf script "synth" field displays "ptwrite" information like this: "ip: 0 payload: 0x123456789abcdef0" where "ip" is 1 if "fup_on_ptw" was used. @@ -960,7 +1018,7 @@ used. "Power" events correspond to power event packets and CBR (core-to-bus ratio) packets. While CBR packets are always recorded when tracing is enabled, power event packets are recorded only if the "pwr_evt" config term was used. Refer to -the config terms section above. The power events record information about +the <<_config_terms,config terms>> section above. The power events record information about C-state changes, whereas CBR is indicative of CPU frequency. perf script "event,synth" fields display information like this: @@ -1116,7 +1174,7 @@ What *will* be decoded with the (single) q option: - asynchronous branches such as interrupts - indirect branches - function return target address *if* the noretcomp config term (refer - config terms section) was used + <<_config_terms,config terms>> section) was used - start of (control-flow) tracing - end of (control-flow) tracing, if it is not out of context - power events, ptwrite, transaction start and abort @@ -1129,7 +1187,7 @@ Repeating the q option (double-q i.e. qq) results in even faster decoding and ev less detail. The decoder decodes only extended PSB (PSB+) packets, getting the instruction pointer if there is a FUP packet within PSB+ (i.e. between PSB and PSBEND). Note PSB packets occur regularly in the trace based on the psb_period -config term (refer config terms section). There will be a FUP packet if the +config term (refer <<_config_terms,config terms>> section). There will be a FUP packet if the PSB+ occurs while control flow is being traced. What will *not* be decoded with the qq option: @@ -1306,7 +1364,7 @@ Without timestamps, --per-thread must be specified to distinguish threads. perf script can be used to provide an instruction trace - $ perf script --guestkallsyms $KALLSYMS --insn-trace --xed -F+ipc | grep -C10 vmresume | head -21 + $ perf script --guestkallsyms $KALLSYMS --insn-trace=disasm -F+ipc | grep -C10 vmresume | head -21 CPU 0/KVM 1440 ffffffff82133cdd __vmx_vcpu_run+0x3d ([kernel.kallsyms]) movq 0x48(%rax), %r9 CPU 0/KVM 1440 ffffffff82133ce1 __vmx_vcpu_run+0x41 ([kernel.kallsyms]) movq 0x50(%rax), %r10 CPU 0/KVM 1440 ffffffff82133ce5 __vmx_vcpu_run+0x45 ([kernel.kallsyms]) movq 0x58(%rax), %r11 @@ -1407,7 +1465,7 @@ There were none. 'perf script' can be used to provide an instruction trace showing timestamps - $ perf script -i perf.data.kvm --guestkallsyms $KALLSYMS --insn-trace --xed -F+ipc | grep -C10 vmresume | head -21 + $ perf script -i perf.data.kvm --guestkallsyms $KALLSYMS --insn-trace=disasm -F+ipc | grep -C10 vmresume | head -21 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133cdd __vmx_vcpu_run+0x3d ([kernel.kallsyms]) movq 0x48(%rax), %r9 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ce1 __vmx_vcpu_run+0x41 ([kernel.kallsyms]) movq 0x50(%rax), %r10 CPU 1/KVM 17006 [001] 11500.262865593: ffffffff82133ce5 __vmx_vcpu_run+0x45 ([kernel.kallsyms]) movq 0x58(%rax), %r11 @@ -1863,6 +1921,108 @@ For pipe mode, the order of events and timestamps can presumably be messed up. +Pause or Resume Tracing +----------------------- + +With newer Kernels, it is possible to use other selected events to pause +or resume Intel PT tracing. This is configured by using the "aux-action" +config term: + +"aux-action=pause" is used with events that are to pause Intel PT tracing. + +"aux-action=resume" is used with events that are to resume Intel PT tracing. + +"aux-action=start-paused" is used with the Intel PT event to start in a +paused state. + +For example, to trace only the uname system call (sys_newuname) when running the +command line utility uname: + + $ perf record --kcore -e intel_pt/aux-action=start-paused/k,syscalls:sys_enter_newuname/aux-action=resume/,syscalls:sys_exit_newuname/aux-action=pause/ uname + Linux + [ perf record: Woken up 1 times to write data ] + [ perf record: Captured and wrote 0.043 MB perf.data ] + $ perf script --call-trace + uname 30805 [000] 24001.058782799: name: 0x7ffc9c1865b0 + uname 30805 [000] 24001.058784424: psb offs: 0 + uname 30805 [000] 24001.058784424: cbr: 39 freq: 3904 MHz (139%) + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __x64_sys_newuname + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) down_read + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __cond_resched + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) in_lock_functions + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_sub + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) up_read + uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) in_lock_functions + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) preempt_count_sub + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) _copy_to_user + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_to_user_mode + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_work + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) perf_syscall_exit + uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_alloc + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_get_recursion_context + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_tp_event + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_update + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) tracing_gen_ctx_irq_test + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_event + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __perf_event_account_interrupt + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __this_cpu_preempt_check + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_output_forward + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_aux_pause + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) ring_buffer_get + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_lock + uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_unlock + uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) pt_event_stop + uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id + uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) native_write_msr + uname 30805 [000] 24001.058785463: ([kernel.kallsyms]) native_write_msr + uname 30805 [000] 24001.058785639: 0x0 + +The example above uses tracepoints, but any kind of sampled event can be used. + +For example: + + Tracing between arch_cpu_idle_enter() and arch_cpu_idle_exit() using breakpoint events: + + $ sudo cat /proc/kallsyms | sort | grep ' arch_cpu_idle_enter\| arch_cpu_idle_exit' + ffffffffb605bf60 T arch_cpu_idle_enter + ffffffffb614d8a0 W arch_cpu_idle_exit + $ sudo perf record --kcore -a -e intel_pt/aux-action=start-paused/k -e mem:0xffffffffb605bf60:x/aux-action=resume/ -e mem:0xffffffffb614d8a0:x/aux-action=pause/ -- sleep 1 + [ perf record: Woken up 1 times to write data ] + [ perf record: Captured and wrote 1.387 MB perf.data ] + + Tracing __alloc_pages() using kprobes: + + $ sudo perf probe --add '__alloc_pages order' + Added new event: probe:__alloc_pages (on __alloc_pages with order) + $ sudo perf probe --add __alloc_pages%return + Added new event: probe:__alloc_pages__return (on __alloc_pages%return) + $ sudo perf record --kcore -aR -e intel_pt/aux-action=start-paused/k -e probe:__alloc_pages/aux-action=resume/ -e probe:__alloc_pages__return/aux-action=pause/ -- sleep 1 + [ perf record: Woken up 1 times to write data ] + [ perf record: Captured and wrote 1.490 MB perf.data ] + + Tracing starting at main() using a uprobe event: + + $ sudo perf probe -x /usr/bin/uname main + Added new event: probe_uname:main (on main in /usr/bin/uname) + $ sudo perf record -e intel_pt/-aux-action=start-paused/u -e probe_uname:main/aux-action=resume/ -- uname + Linux + [ perf record: Woken up 1 times to write data ] + [ perf record: Captured and wrote 0.031 MB perf.data ] + + Tracing occasionally using cycles events with different periods: + + $ perf record --kcore -a -m,64M -e intel_pt/aux-action=start-paused/k -e cycles/aux-action=pause,period=1000000/Pk -e cycles/aux-action=resume,period=10500000/Pk -- firefox + [ perf record: Woken up 19 times to write data ] + [ perf record: Captured and wrote 16.561 MB perf.data ] + + EXAMPLE ------- |