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From: Adrian Hunter <adrian.hunter@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
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	Suzuki K Poulose <suzuki.poulose@arm.com>,
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	Jonathan Cameron <jonathan.cameron@huawei.com>,
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	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Jiri Olsa <jolsa@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
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	linux-perf-users@vger.kernel.org
Subject: [PATCH V5 11/12] perf intel-pt: Add documentation for pause / resume
Date: Thu,  8 Feb 2024 13:31:26 +0200
Message-Id: <20240208113127.22216-12-adrian.hunter@intel.com>
In-Reply-To: <20240208113127.22216-1-adrian.hunter@intel.com>
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Document the use of aux-action config term and provide a simple example.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ian Rogers <irogers@google.com>
---


Changes in V5:
	Added more examples


 tools/perf/Documentation/perf-intel-pt.txt | 108 +++++++++++++++++++++
 1 file changed, 108 insertions(+)

diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
index b5fa7c7ad7f5..c86deae170e4 100644
--- a/tools/perf/Documentation/perf-intel-pt.txt
+++ b/tools/perf/Documentation/perf-intel-pt.txt
@@ -551,6 +551,9 @@ Support for this feature is indicated by:
 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
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -566,6 +569,9 @@ and PEBS-via-PT.  In those cases, the other events can have config terms below:
 		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
 ~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1911,6 +1917,108 @@ 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 occassionally 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
 -------
 
-- 
2.34.1