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perf intel-pt: Add documentation for pause / resume
Document the use of aux-action config term and provide a simple example. Reviewed-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Acked-by: Ian Rogers <irogers@google.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Leo Yan <leo.yan@arm.com> Cc: Namhyung Kim <namhyung@kernel.org> Link: https://lore.kernel.org/r/20241216070244.14450-7-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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Adrian Hunter
Arnaldo Carvalho de Melo
parent
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f8b301e0a4
@ -555,6 +555,9 @@ Support for this feature is indicated by:
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which contains "1" if the feature is supported and
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"0" otherwise.
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*aux-action=start-paused*::
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Start tracing paused, refer to the section <<_pause_or_resume_tracing,Pause or Resume Tracing>>
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config terms on other events
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@ -570,6 +573,9 @@ and PEBS-via-PT. In those cases, the other events can have config terms below:
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Used to select PEBS-via-PT, refer to the
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section <<_pebs_via_intel_pt,PEBS via Intel PT>>
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*aux-action*::
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Used to pause or resume tracing, refer to the section
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<<_pause_or_resume_tracing,Pause or Resume Tracing>>
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AUX area sampling option
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~~~~~~~~~~~~~~~~~~~~~~~~
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@ -1915,6 +1921,108 @@ For pipe mode, the order of events and timestamps can presumably
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be messed up.
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Pause or Resume Tracing
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-----------------------
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With newer Kernels, it is possible to use other selected events to pause
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or resume Intel PT tracing. This is configured by using the "aux-action"
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config term:
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"aux-action=pause" is used with events that are to pause Intel PT tracing.
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"aux-action=resume" is used with events that are to resume Intel PT tracing.
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"aux-action=start-paused" is used with the Intel PT event to start in a
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paused state.
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For example, to trace only the uname system call (sys_newuname) when running the
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command line utility uname:
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$ 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
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Linux
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[ perf record: Woken up 1 times to write data ]
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[ perf record: Captured and wrote 0.043 MB perf.data ]
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$ perf script --call-trace
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uname 30805 [000] 24001.058782799: name: 0x7ffc9c1865b0
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uname 30805 [000] 24001.058784424: psb offs: 0
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uname 30805 [000] 24001.058784424: cbr: 39 freq: 3904 MHz (139%)
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __x64_sys_newuname
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) down_read
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) __cond_resched
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) in_lock_functions
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_sub
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) up_read
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uname 30805 [000] 24001.058784629: ([kernel.kallsyms]) preempt_count_add
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) in_lock_functions
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) preempt_count_sub
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) _copy_to_user
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_to_user_mode
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) syscall_exit_work
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) perf_syscall_exit
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uname 30805 [000] 24001.058784838: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_alloc
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_get_recursion_context
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_tp_event
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_trace_buf_update
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) tracing_gen_ctx_irq_test
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_swevent_event
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __perf_event_account_interrupt
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __this_cpu_preempt_check
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_output_forward
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) perf_event_aux_pause
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) ring_buffer_get
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_lock
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uname 30805 [000] 24001.058785046: ([kernel.kallsyms]) __rcu_read_unlock
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uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) pt_event_stop
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uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) debug_smp_processor_id
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uname 30805 [000] 24001.058785254: ([kernel.kallsyms]) native_write_msr
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uname 30805 [000] 24001.058785463: ([kernel.kallsyms]) native_write_msr
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uname 30805 [000] 24001.058785639: 0x0
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The example above uses tracepoints, but any kind of sampled event can be used.
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For example:
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Tracing between arch_cpu_idle_enter() and arch_cpu_idle_exit() using breakpoint events:
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$ sudo cat /proc/kallsyms | sort | grep ' arch_cpu_idle_enter\| arch_cpu_idle_exit'
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ffffffffb605bf60 T arch_cpu_idle_enter
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ffffffffb614d8a0 W arch_cpu_idle_exit
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$ 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
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[ perf record: Woken up 1 times to write data ]
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[ perf record: Captured and wrote 1.387 MB perf.data ]
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Tracing __alloc_pages() using kprobes:
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$ sudo perf probe --add '__alloc_pages order'
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Added new event: probe:__alloc_pages (on __alloc_pages with order)
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$ sudo perf probe --add __alloc_pages%return
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Added new event: probe:__alloc_pages__return (on __alloc_pages%return)
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$ 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
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[ perf record: Woken up 1 times to write data ]
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[ perf record: Captured and wrote 1.490 MB perf.data ]
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Tracing starting at main() using a uprobe event:
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$ sudo perf probe -x /usr/bin/uname main
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Added new event: probe_uname:main (on main in /usr/bin/uname)
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$ sudo perf record -e intel_pt/-aux-action=start-paused/u -e probe_uname:main/aux-action=resume/ -- uname
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Linux
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[ perf record: Woken up 1 times to write data ]
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[ perf record: Captured and wrote 0.031 MB perf.data ]
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Tracing occasionally using cycles events with different periods:
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$ 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
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[ perf record: Woken up 19 times to write data ]
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[ perf record: Captured and wrote 16.561 MB perf.data ]
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EXAMPLE
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-------
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