Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized event

[James Clark]

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@xxxxxxxxxx>
> ---
>  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.



>  
>  	sample->ip = record->from_ip;
>  	sample->cpumode = arm_spe_cpumode(spe, sample->ip);
>