Re: [PATCH 1/3] perf arm-spe: Track task context switch for cpu-mode events

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Sat, Nov 06, 2021 at 11:29:07AM +0800, Leo Yan escreveu:
> Hi German,
> 
> On Tue, Nov 02, 2021 at 06:07:37PM +0000, German Gomez wrote:
> > When perf report synthesize events from ARM SPE data, it refers to
> > current cpu, pid and tid in the machine.  But there's no place to set
> > them in the ARM SPE decoder.  I'm seeing all pid/tid is set to -1 and
> > user symbols are not resolved in the output.
> > 
> >   # perf record -a -e arm_spe_0/ts_enable=1/ sleep 1
> > 
> >   # perf report -q | head
> >      8.77%     8.77%  :-1      [kernel.kallsyms]  [k] format_decode
> >      7.02%     7.02%  :-1      [kernel.kallsyms]  [k] seq_printf
> >      7.02%     7.02%  :-1      [unknown]          [.] 0x0000ffff9f687c34
> >      5.26%     5.26%  :-1      [kernel.kallsyms]  [k] vsnprintf
> >      3.51%     3.51%  :-1      [kernel.kallsyms]  [k] string
> >      3.51%     3.51%  :-1      [unknown]          [.] 0x0000ffff9f66ae20
> >      3.51%     3.51%  :-1      [unknown]          [.] 0x0000ffff9f670b3c
> >      3.51%     3.51%  :-1      [unknown]          [.] 0x0000ffff9f67c040
> >      1.75%     1.75%  :-1      [kernel.kallsyms]  [k] ___cache_free
> >      1.75%     1.75%  :-1      [kernel.kallsyms]  [k]
> > __count_memcg_events
> > 
> > Like Intel PT, add context switch records to track task info.  As ARM
> > SPE support was added later than PERF_RECORD_SWITCH_CPU_WIDE, I think
> > we can safely set the attr.context_switch bit and use it.
> > 
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > Signed-off-by: German Gomez <german.gomez@arm.com>
> 
> Reviewed-by: Leo Yan <leo.yan@linaro.org>
> 
> Note for one thing, please keep "Namhyung Kim" as the author for this
> patch, thanks.

This merits a v2 submission, please do so.

- Arnaldo
 
> Leo
> 
> > ---
> >  tools/perf/arch/arm64/util/arm-spe.c |  6 +++++-
> >  tools/perf/util/arm-spe.c            | 25 +++++++++++++++++++++++++
> >  2 files changed, 30 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
> > index a4420d4df..58ba8d15c 100644
> > --- a/tools/perf/arch/arm64/util/arm-spe.c
> > +++ b/tools/perf/arch/arm64/util/arm-spe.c
> > @@ -166,8 +166,12 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
> >  	tracking_evsel->core.attr.sample_period = 1;
> >  
> >  	/* In per-cpu case, always need the time of mmap events etc */
> > -	if (!perf_cpu_map__empty(cpus))
> > +	if (!perf_cpu_map__empty(cpus)) {
> >  		evsel__set_sample_bit(tracking_evsel, TIME);
> > +		evsel__set_sample_bit(tracking_evsel, CPU);
> > +		/* also track task context switch */
> > +		tracking_evsel->core.attr.context_switch = 1;
> > +	}
> >  
> >  	return 0;
> >  }
> > diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c
> > index 58b7069c5..230bc7ab2 100644
> > --- a/tools/perf/util/arm-spe.c
> > +++ b/tools/perf/util/arm-spe.c
> > @@ -681,6 +681,25 @@ static int arm_spe_process_timeless_queues(struct arm_spe *spe, pid_t tid,
> >  	return 0;
> >  }
> >  
> > +static int arm_spe_context_switch(struct arm_spe *spe, union perf_event *event,
> > +				  struct perf_sample *sample)
> > +{
> > +	pid_t pid, tid;
> > +	int cpu;
> > +
> > +	if (!(event->header.misc & PERF_RECORD_MISC_SWITCH_OUT))
> > +		return 0;
> > +
> > +	pid = event->context_switch.next_prev_pid;
> > +	tid = event->context_switch.next_prev_tid;
> > +	cpu = sample->cpu;
> > +
> > +	if (tid == -1)
> > +		pr_warning("context_switch event has no tid\n");
> > +
> > +	return machine__set_current_tid(spe->machine, cpu, pid, tid);
> > +}
> > +
> >  static int arm_spe_process_event(struct perf_session *session,
> >  				 union perf_event *event,
> >  				 struct perf_sample *sample,
> > @@ -718,6 +737,12 @@ static int arm_spe_process_event(struct perf_session *session,
> >  		}
> >  	} else if (timestamp) {
> >  		err = arm_spe_process_queues(spe, timestamp);
> > +		if (err)
> > +			return err;
> > +
> > +		if (event->header.type == PERF_RECORD_SWITCH_CPU_WIDE ||
> > +		    event->header.type == PERF_RECORD_SWITCH)
> > +			err = arm_spe_context_switch(spe, event, sample);
> >  	}
> >  
> >  	return err;
> > -- 
> > 2.25.1
> > 

-- 

- Arnaldo