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Subject: Re: [PATCH v4 4/6] perf arm-spe: Assign kernel time to synthesized
 event
To:     Leo Yan <leo.yan@linaro.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Al Grant <Al.Grant@arm.com>,
        John Garry <john.garry@huawei.com>,
        Will Deacon <will@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Dave Martin <Dave.Martin@arm.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20210412091006.468557-1-leo.yan@linaro.org>
 <20210412091006.468557-5-leo.yan@linaro.org>
From:   James Clark <james.clark@arm.com>
Message-ID: <9036368a-e824-3d63-da5b-54cf32a86aed@arm.com>
Date:   Thu, 15 Apr 2021 17:46:31 +0300
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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.


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