linux-kernel - Re: [PATCH V4 10/11] perf intel-pt: Add documentation for pause / resume

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Date: Tue, 16 Jan 2024 14:22:01 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Andi Kleen <ak@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Heiko Carstens <hca@...ux.ibm.com>, Thomas Richter <tmricht@...ux.ibm.com>,
 Hendrik Brueckner <brueckner@...ux.ibm.com>,
 Suzuki K Poulose <suzuki.poulose@....com>, Mike Leach
 <mike.leach@...aro.org>, James Clark <james.clark@....com>,
 coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 Yicong Yang <yangyicong@...ilicon.com>,
 Jonathan Cameron <jonathan.cameron@...wei.com>, Will Deacon
 <will@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Ian Rogers <irogers@...gle.com>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org
Subject: Re: [PATCH V4 10/11] perf intel-pt: Add documentation for pause /
 resume

On 16/01/24 13:15, Andi Kleen wrote:
> Adrian Hunter <adrian.hunter@...el.com> writes:
>> +
>> +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
> 
> It's unclear if the syntax works for hardware break points, kprobes, uprobes too?

Yes, the perf tool syntax requires only that the group leader is
an AUX area event like intel_pt.  Note that an attempt is made to
automatically group AUX area events with events with aux-action,
so grouping syntax like '{...}' is not always necessary.

Note the current kernel implementation is called from
__perf_event_output() which is used in nearly all cases for the
output of samples, the exceptions being Intel BTS (which we do not
support at the same time as Intel PT, but wouldn't make much sense
anyway) and S390 cpumsf_output_event_pid().

> That would be most useful. If it works would be good to add examples for it.

OK