Messages in this thread | | | Subject | Re: [PATCH 8/8] perf arm-spe: Set thread TID | From | James Clark <> | Date | Tue, 9 Feb 2021 17:36:11 +0200 |
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On 04/02/2021 12:27, Leo Yan wrote: > On Mon, Feb 01, 2021 at 07:40:45PM +0200, James Clark wrote: >> >> On 31/01/2021 14:01, Leo Yan wrote: >>> Option 1: by merging patches 07/08 and 08/08, we can firstly support PID >>> tracing for root namespace, and later we can extend to support PID >>> tracing in container (and in VMs). >>> > Arm SPE has the problem for step2, due to the trace uses statistical > approach, it doesn't trace the complete branch instructions, so it > cannot promise to capture all branches for the symbol "__switch_to". > If we only use the events PERF_RECORD_SWITCH / > PERF_RECORD_SWITCH_CPU_WIDE, then it will lead to the coarse result > for PID tracing. > > For this reason, seems to me it's pragmatic to use CONTEXTIDR for > PID tracing at current stage, at least it can allow the root domain > tracing works accurately. But this will leave the issue for tracing > PID in non root namespace, we need to figure out solution later. > > Hi Mark.R, Al, do you have any comments for this?
Hi Leo,
I spoke with Al and his suggestion is to clear the PID value if the event was opened outside of the root namespace.
I think that's not a bad idea as it gets us PIDs in most cases but also doesn't show any incorrect data. Do you know if it's possible to determine that from a perf.data file? Unfortunately it doesn't seem to be possible to disable CONTEXTIDR tracing when opening the event as it's compile time only and can't be disabled dynamically.
James
> > Thanks, > Leo > >>>> Signed-off-by: Leo Yan <leo.yan@linaro.org> >>>> Signed-off-by: James Clark <james.clark@arm.com> >>> >>> Besides for techinical question, you could add your "Co-developed-by" >>> tags for patches 06, 07, 08/08, which you have took time to refin them. >>> >>> Thanks you for kindly efforts. >>> >>> [1] https://lore.kernel.org/patchwork/patch/1353286/ >>> >>>> Cc: Peter Zijlstra <peterz@infradead.org> >>>> Cc: Ingo Molnar <mingo@redhat.com> >>>> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> >>>> Cc: Mark Rutland <mark.rutland@arm.com> >>>> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> >>>> Cc: Jiri Olsa <jolsa@redhat.com> >>>> Cc: Namhyung Kim <namhyung@kernel.org> >>>> Cc: John Garry <john.garry@huawei.com> >>>> Cc: Will Deacon <will@kernel.org> >>>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> >>>> Cc: Al Grant <al.grant@arm.com> >>>> Cc: Andre Przywara <andre.przywara@arm.com> >>>> Cc: Wei Li <liwei391@huawei.com> >>>> Cc: Tan Xiaojun <tanxiaojun@huawei.com> >>>> Cc: Adrian Hunter <adrian.hunter@intel.com> >>>> --- >>>> tools/perf/util/arm-spe.c | 75 ++++++++++++++++++++++++++------------- >>>> 1 file changed, 50 insertions(+), 25 deletions(-) >>>> >>>> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c >>>> index 27a0b9dfe22d..9828fad7e516 100644 >>>> --- a/tools/perf/util/arm-spe.c >>>> +++ b/tools/perf/util/arm-spe.c >>>> @@ -223,6 +223,46 @@ static inline u8 arm_spe_cpumode(struct arm_spe *spe, u64 ip) >>>> PERF_RECORD_MISC_USER; >>>> } >>>> >>>> +static void arm_spe_set_pid_tid_cpu(struct arm_spe *spe, >>>> + struct auxtrace_queue *queue) >>>> +{ >>>> + struct arm_spe_queue *speq = queue->priv; >>>> + pid_t tid; >>>> + >>>> + tid = machine__get_current_tid(spe->machine, speq->cpu); >>>> + if (tid != -1) { >>>> + speq->tid = tid; >>>> + thread__zput(speq->thread); >>>> + } else >>>> + speq->tid = queue->tid; >>>> + >>>> + if ((!speq->thread) && (speq->tid != -1)) { >>>> + speq->thread = machine__find_thread(spe->machine, -1, >>>> + speq->tid); >>>> + } >>>> + >>>> + if (speq->thread) { >>>> + speq->pid = speq->thread->pid_; >>>> + if (queue->cpu == -1) >>>> + speq->cpu = speq->thread->cpu; >>>> + } >>>> +} >>>> + >>>> +static int arm_spe_set_tid(struct arm_spe_queue *speq, pid_t tid) >>>> +{ >>>> + int err; >>>> + struct arm_spe *spe = speq->spe; >>>> + struct auxtrace_queue *queue; >>>> + >>>> + err = machine__set_current_tid(spe->machine, speq->cpu, tid, tid); >>>> + if (err) >>>> + return err; >>>> + >>>> + queue = &speq->spe->queues.queue_array[speq->queue_nr]; >>>> + arm_spe_set_pid_tid_cpu(speq->spe, queue); >>>> + return 0; >>>> +} >>>> + >>>> static void arm_spe_prep_sample(struct arm_spe *spe, >>>> struct arm_spe_queue *speq, >>>> union perf_event *event, >>>> @@ -431,6 +471,7 @@ static int arm_spe_sample(struct arm_spe_queue *speq) >>>> static int arm_spe_run_decoder(struct arm_spe_queue *speq, u64 *timestamp) >>>> { >>>> struct arm_spe *spe = speq->spe; >>>> + const struct arm_spe_record *record; >>>> int ret; >>>> >>>> if (!spe->kernel_start) >>>> @@ -450,6 +491,11 @@ static int arm_spe_run_decoder(struct arm_spe_queue *speq, u64 *timestamp) >>>> if (ret < 0) >>>> continue; >>>> >>>> + record = &speq->decoder->record; >>>> + ret = arm_spe_set_tid(speq, record->context_id); >>>> + if (ret) >>>> + return ret; >>>> + >>>> ret = arm_spe_sample(speq); >>>> if (ret) >>>> return ret; >>>> @@ -500,6 +546,10 @@ static int arm_spe__setup_queue(struct arm_spe *spe, >>>> >>>> record = &speq->decoder->record; >>>> >>>> + ret = arm_spe_set_tid(speq, record->context_id); >>>> + if (ret) >>>> + return ret; >>>> + >>>> speq->timestamp = record->timestamp; >>>> ret = auxtrace_heap__add(&spe->heap, queue_nr, speq->timestamp); >>>> if (ret) >>>> @@ -552,31 +602,6 @@ static bool arm_spe__is_timeless_decoding(struct arm_spe *spe) >>>> return timeless_decoding; >>>> } >>>> >>>> -static void arm_spe_set_pid_tid_cpu(struct arm_spe *spe, >>>> - struct auxtrace_queue *queue) >>>> -{ >>>> - struct arm_spe_queue *speq = queue->priv; >>>> - pid_t tid; >>>> - >>>> - tid = machine__get_current_tid(spe->machine, speq->cpu); >>>> - if (tid != -1) { >>>> - speq->tid = tid; >>>> - thread__zput(speq->thread); >>>> - } else >>>> - speq->tid = queue->tid; >>>> - >>>> - if ((!speq->thread) && (speq->tid != -1)) { >>>> - speq->thread = machine__find_thread(spe->machine, -1, >>>> - speq->tid); >>>> - } >>>> - >>>> - if (speq->thread) { >>>> - speq->pid = speq->thread->pid_; >>>> - if (queue->cpu == -1) >>>> - speq->cpu = speq->thread->cpu; >>>> - } >>>> -} >>>> - >>>> static int arm_spe_process_queues(struct arm_spe *spe, u64 timestamp) >>>> { >>>> unsigned int queue_nr; >>>> -- >>>> 2.28.0 >>>>
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