linux-kernel - Re: [PATCH 2/2] perf evlist: Support pipe mode display

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Date:   Mon, 14 Dec 2020 00:00:35 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH 2/2] perf evlist: Support pipe mode display

On Thu, Dec 10, 2020 at 03:13:02PM +0900, Namhyung Kim wrote:
> Likewise, perf evlist command should print event attributes by reading
> PERF_RECORD_HEADER_ATTR records.
> 
> Before:
>   $ perf record -o- true | ./perf evlist -i-
>   (prints nothing)
> 
> After:
>   $ perf record -o- true | ./perf evlist -i-
>   cycles:pppH
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>

Acked-by: Jiri Olsa <jolsa@...hat.com>

thanks,
jirka

> ---
>  tools/perf/builtin-evlist.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-evlist.c b/tools/perf/builtin-evlist.c
> index 98e992801251..4617b32c9c97 100644
> --- a/tools/perf/builtin-evlist.c
> +++ b/tools/perf/builtin-evlist.c
> @@ -17,6 +17,14 @@
>  #include "util/data.h"
>  #include "util/debug.h"
>  #include <linux/err.h>
> +#include "util/tool.h"
> +
> +static int process_header_feature(struct perf_session *session __maybe_unused,
> +				  union perf_event *event __maybe_unused)
> +{
> +	session_done = 1;
> +	return 0;
> +}
>  
>  static int __cmd_evlist(const char *file_name, struct perf_attr_details *details)
>  {
> @@ -27,12 +35,20 @@ static int __cmd_evlist(const char *file_name, struct perf_attr_details *details
>  		.mode      = PERF_DATA_MODE_READ,
>  		.force     = details->force,
>  	};
> +	struct perf_tool tool = {
> +		/* only needed for pipe mode */
> +		.attr = perf_event__process_attr,
> +		.feature = process_header_feature,
> +	};
>  	bool has_tracepoint = false;
>  
> -	session = perf_session__new(&data, 0, NULL);
> +	session = perf_session__new(&data, 0, &tool);
>  	if (IS_ERR(session))
>  		return PTR_ERR(session);
>  
> +	if (data.is_pipe)
> +		perf_session__process_events(session);
> +
>  	evlist__for_each_entry(session->evlist, pos) {
>  		evsel__fprintf(pos, details, stdout);
>  
> -- 
> 2.29.2.576.ga3fc446d84-goog
>