linux-kernel - Re: [PATCH v1 1/2] perf auxtrace: Add 'T' itrace option for timestamp trace

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Date:   Thu, 19 Oct 2023 13:47:15 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        James Clark <james.clark@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>
Cc:     John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] perf auxtrace: Add 'T' itrace option for timestamp
 trace

On 14/10/23 10:45, Leo Yan wrote:
> An AUX trace can contain timestamp, but in some situations, the hardware
> trace module (e.g. Arm CoreSight) cannot decide the traced timestamp is
> the same source with CPU's time, thus the decoder can not use the
> timestamp trace for samples.
> 
> This patch introduces 'T' itrace option. If users know the platforms

"If users know" <- how would users know?  Could the kernel
or tools also figure it out?

> they are working on have the same time counter with CPUs, users can
> use this new option to tell a decoder for using timestamp trace as
> kernel time.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/Documentation/itrace.txt | 1 +
>  tools/perf/util/auxtrace.c          | 3 +++
>  tools/perf/util/auxtrace.h          | 3 +++
>  3 files changed, 7 insertions(+)
> 
> diff --git a/tools/perf/Documentation/itrace.txt b/tools/perf/Documentation/itrace.txt
> index a97f95825b14..19cc179be9a7 100644
> --- a/tools/perf/Documentation/itrace.txt
> +++ b/tools/perf/Documentation/itrace.txt
> @@ -25,6 +25,7 @@
>  		q	quicker (less detailed) decoding
>  		A	approximate IPC
>  		Z	prefer to ignore timestamps (so-called "timeless" decoding)
> +		T	use the timestamp trace as kernel time
>  
>  	The default is all events i.e. the same as --itrace=iybxwpe,
>  	except for perf script where it is --itrace=ce
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index a0368202a746..f528c4364d23 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -1638,6 +1638,9 @@ int itrace_do_parse_synth_opts(struct itrace_synth_opts *synth_opts,
>  		case 'Z':
>  			synth_opts->timeless_decoding = true;
>  			break;
> +		case 'T':
> +			synth_opts->use_timestamp = true;
> +			break;
>  		case ' ':
>  		case ',':
>  			break;
> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> index 29eb82dff574..55702215a82d 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -99,6 +99,7 @@ enum itrace_period_type {
>   * @remote_access: whether to synthesize remote access events
>   * @mem: whether to synthesize memory events
>   * @timeless_decoding: prefer "timeless" decoding i.e. ignore timestamps
> + * @use_timestamp: use the timestamp trace as kernel time
>   * @vm_time_correlation: perform VM Time Correlation
>   * @vm_tm_corr_dry_run: VM Time Correlation dry-run
>   * @vm_tm_corr_args:  VM Time Correlation implementation-specific arguments
> @@ -146,6 +147,7 @@ struct itrace_synth_opts {
>  	bool			remote_access;
>  	bool			mem;
>  	bool			timeless_decoding;
> +	bool			use_timestamp;
>  	bool			vm_time_correlation;
>  	bool			vm_tm_corr_dry_run;
>  	char			*vm_tm_corr_args;
> @@ -678,6 +680,7 @@ bool auxtrace__evsel_is_auxtrace(struct perf_session *session,
>  "				q:			quicker (less detailed) decoding\n" \
>  "				A:			approximate IPC\n" \
>  "				Z:			prefer to ignore timestamps (so-called \"timeless\" decoding)\n" \
> +"				T:			use the timestamp trace as kernel time\n" \
>  "				PERIOD[ns|us|ms|i|t]:   specify period to sample stream\n" \
>  "				concatenate multiple options. Default is iybxwpe or cewp\n"
>