linux-kernel - Re: [PATCH 3/3] perf inject: Do not load map/dso when injecting build-id

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Date:   Tue, 15 Sep 2020 12:05:33 +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>,
        Stephane Eranian <eranian@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH 3/3] perf inject: Do not load map/dso when injecting
 build-id

On Mon, Sep 14, 2020 at 11:18:59PM +0900, Namhyung Kim wrote:
> No need to load symbols in a DSO when injecting build-id.  I guess the
> reason was to check the DSO is a special file like anon files.  Use
> some helper functions in map.c to check them before reading build-id.
> Also pass sample event's cpumode to a new build-id event.
> 
> Original-patch-by: Stephane Eranian <eranian@...gle.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-inject.c | 30 ++++++++++--------------------
>  tools/perf/util/map.c       | 17 +----------------
>  tools/perf/util/map.h       | 14 ++++++++++++++
>  3 files changed, 25 insertions(+), 36 deletions(-)
> 
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index a2804d906d2a..6d4e6833efed 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -436,21 +436,22 @@ static int dso__read_build_id(struct dso *dso)
>  }
>  
>  static int dso__inject_build_id(struct dso *dso, struct perf_tool *tool,
> -				struct machine *machine)
> +				struct machine *machine, u8 cpumode)
>  {
> -	u16 misc = PERF_RECORD_MISC_USER;
>  	int err;
>  
> +	if (is_anon_memory(dso->long_name))
> +		return 0;
> +	if (is_no_dso_memory(dso->long_name))
> +		return 0;

should we check for vdso as well? I don't think it has build id

> +
>  	if (dso__read_build_id(dso) < 0) {
>  		pr_debug("no build_id found for %s\n", dso->long_name);
>  		return -1;
>  	}
>  
> -	if (dso->kernel)
> -		misc = PERF_RECORD_MISC_KERNEL;
> -
> -	err = perf_event__synthesize_build_id(tool, dso, misc, perf_event__repipe,
> -					      machine);
> +	err = perf_event__synthesize_build_id(tool, dso, cpumode,
> +					      perf_event__repipe, machine);
>  	if (err) {
>  		pr_err("Can't synthesize build_id event for %s\n", dso->long_name);
>  		return -1;
> @@ -478,19 +479,8 @@ static int perf_event__inject_buildid(struct perf_tool *tool,
>  	if (thread__find_map(thread, sample->cpumode, sample->ip, &al)) {
>  		if (!al.map->dso->hit) {
>  			al.map->dso->hit = 1;
> -			if (map__load(al.map) >= 0) {

nice, that might do some nice speedup, did you see any?

jirka

> -				dso__inject_build_id(al.map->dso, tool, machine);
> -				/*
> -				 * If this fails, too bad, let the other side
> -				 * account this as unresolved.
> -				 */
> -			} else {
> -#ifdef HAVE_LIBELF_SUPPORT
> -				pr_warning("no symbols found in %s, maybe "
> -					   "install a debug package?\n",
> -					   al.map->dso->long_name);
> -#endif
> -			}
> +			dso__inject_build_id(al.map->dso, tool, machine,
> +					     sample->cpumode);
>  		}

SNIP