linux-kernel - Re: [PATCH 7/7] perf inject: Remove stale build-id processing

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Date:   Thu, 24 Sep 2020 15:33:49 +0200
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 <a.p.zijlstra@...llo.nl>,
        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>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH 7/7] perf inject: Remove stale build-id processing

On Wed, Sep 23, 2020 at 05:05:37PM +0900, Namhyung Kim wrote:
> I think we don't need to call build_id__mark_dso_hit() in the
> perf_event__repipe_sample() as it's not used by -b option.  In case of
> the -b option is used, it uses perf_event__inject_buildid() instead.
> This can remove unnecessary overhead of finding thread/map for each
> sample event.
> 
> Also I suspect HEADER_BUILD_ID feature bit setting since we already
> generated/injected BUILD_ID event into the output stream.  So this
> header information seems redundant.  I'm not 100% sure about the
> auxtrace usage, but it looks like not related to this directly.
> 
> And we now have --buildid-all so users can get the same behavior if
> they want.
> 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-inject.c | 12 ------------
>  1 file changed, 12 deletions(-)
> 
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index 500428aaa576..0191d72be7c4 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -277,8 +277,6 @@ static int perf_event__repipe_sample(struct perf_tool *tool,
>  		return f(tool, event, sample, evsel, machine);
>  	}
>  
> -	build_id__mark_dso_hit(tool, event, sample, evsel, machine);
> -

I recalled using simple 'perf inject -i .. -o .. ' to get uncompressed data
from 'perf record -z' and I though this change will force inject not to store
all build ids ... but it's happening even without your change ;-)

	$ ./perf record ls
	...
	[ perf record: Woken up 1 times to write data ]
	[ perf record: Captured and wrote 0.016 MB perf.data (15 samples) ]

	$ ./perf inject -o perf.data.new -i perf.data

	$ ./perf buildid-list

	17f4e448cc746582ea1881528deb549f7fdb3fd5 [kernel.kallsyms]
	b516839521ded07bb1fbd0a0276be9820ee8908e /usr/bin/ls
	1805c738c8f3ec0f47b7ea09080c28f34d18a82b /usr/lib64/ld-2.31.so
	f22785ea7e42e8aa9097a567a3cc8ae214cae4b6 [vdso]
	d278249792061c6b74d1693ca59513be1def13f2 /usr/lib64/libc-2.31.so

	$ ./perf buildid-list -i perf.data.new
	f22785ea7e42e8aa9097a567a3cc8ae214cae4b6 [vdso]

jirka


>  	if (inject->itrace_synth_opts.set && sample->aux_sample.size)
>  		event = perf_inject__cut_auxtrace_sample(inject, event, sample);
>  
> @@ -767,16 +765,6 @@ static int __cmd_inject(struct perf_inject *inject)
>  		return ret;
>  
>  	if (!data_out->is_pipe) {
> -		if (inject->build_ids)
> -			perf_header__set_feat(&session->header,
> -					      HEADER_BUILD_ID);
> -		/*
> -		 * Keep all buildids when there is unprocessed AUX data because
> -		 * it is not known which ones the AUX trace hits.
> -		 */
> -		if (perf_header__has_feat(&session->header, HEADER_BUILD_ID) &&
> -		    inject->have_auxtrace && !inject->itrace_synth_opts.set)
> -			dsos__hit_all(session);
>  		/*
>  		 * The AUX areas have been removed and replaced with
>  		 * synthesized hardware events, so clear the feature flag and
> -- 
> 2.28.0.681.g6f77f65b4e-goog
>