Messages in this thread | | | Subject | Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized event | From | James Clark <> | Date | Fri, 16 Apr 2021 15:51:25 +0300 |
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On 15/04/2021 18:23, Leo Yan wrote: > On Thu, Apr 15, 2021 at 05:46:31PM +0300, James Clark wrote: >> >> >> On 12/04/2021 12:10, Leo Yan wrote: >>> In current code, it assigns the arch timer counter to the synthesized >>> samples Arm SPE trace, thus the samples don't contain the kernel time >>> but only contain the raw counter value. >>> >>> To fix the issue, this patch converts the timer counter to kernel time >>> and assigns it to sample timestamp. >>> >>> Signed-off-by: Leo Yan <leo.yan@linaro.org> >>> --- >>> tools/perf/util/arm-spe.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/tools/perf/util/arm-spe.c b/tools/perf/util/arm-spe.c >>> index 23714cf0380e..c13a89f06ab8 100644 >>> --- a/tools/perf/util/arm-spe.c >>> +++ b/tools/perf/util/arm-spe.c >>> @@ -234,7 +234,7 @@ static void arm_spe_prep_sample(struct arm_spe *spe, >>> struct arm_spe_record *record = &speq->decoder->record; >>> >>> if (!spe->timeless_decoding) >>> - sample->time = speq->timestamp; >>> + sample->time = tsc_to_perf_time(record->timestamp, &spe->tc); >> >> >> I noticed that in arm_spe_recording_options() the TIME sample bit is set regardless of any options. >> I don't know of a way to remove this, and if there isn't, does that mean that all the code in this >> file that looks at spe->timeless_decoding is untested and has never been hit? >> >> Unless there is a way to get a perf file with only the AUXTRACE event and no others? I think that one >> might have no timestamp set. Otherwise other events will always have timestamps so spe->timeless_decoding >> is always false. > > Good point. To be honest, I never noticed this issue until you > mentioned this. > > We should fix for the "timeless" flow; and it's questionable for the > function arm_spe_recording_options(), except for setting > PERF_SAMPLE_TIME, it also hard codes for setting > PERF_SAMPLE_CPU and PERF_SAMPLE_TID. Might need to carefully go > through this function. >
Yeah, it's not strictly related to your change, which is definitely an improvement. But maybe we should have a look at the SPE implementation relating to timestamps as a whole.
> Thanks, > Leo >
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