linux-kernel - Re: [PATCH 1/1 perf-tools-next] perf top: Don't complain about lack of vmlinux when not resolving some kernel samples

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Message-ID: <Z3xFbYjkPz_u1UeK@google.com>
Date: Mon, 6 Jan 2025 13:04:45 -0800
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 1/1 perf-tools-next] perf top: Don't complain about lack
 of vmlinux when not resolving some kernel samples

Hi Arnaldo,

On Fri, Jan 03, 2025 at 01:47:19PM -0300, Arnaldo Carvalho de Melo wrote:
> Recently we got a case where a kernel sample wasn't being resolved due
> to a bug that was not setting the end address on kernel functions
> implemented in assembly (see Link: tag), and then those were not being
> found by machine__resolve() -> map__find_symbol().
> 
> So we ended up with:
> 
>   # perf top --stdio
>   PerfTop: 0 irqs/s  kernel: 0%  exact: 0% lost: 0/0 drop: 0/0 [cycles/P]
>   -----------------------------------------------------------------------
> 
>   Warning:
>   A vmlinux file was not found.
>   Kernel samples will not be resolved.
>   ^Z
>   [1]+  Stopped                 perf top --stdio
>   #
> 
> But then resolving all other kernel symbols.
> 
> So just fixup the logic to only print that warning when there are no
> symbols in the kernel map.
> 
> Cc: Adrian Hunter <adrian.hunter@...el.com>
> Cc: Ian Rogers <irogers@...gle.com>
> Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> Cc: James Clark <james.clark@...aro.org>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Kan Liang <kan.liang@...ux.intel.com>
> Link: https://lore.kernel.org/lkml/Z3buKhcCsZi3_aGb@x1
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>

Reviewed-by: Namhyung Kim <namhyung@...nel.org>

Looks like an old bug since d88205db9caa0e9d ("perf dso: Add
dso__has_symbols() method"). :)

Thanks,
Namhyung

> ---
>  tools/perf/builtin-top.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index 724a7938632126bf..ca3e8eca6610e851 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -809,7 +809,7 @@ static void perf_event__process_sample(const struct perf_tool *tool,
>  		 * invalid --vmlinux ;-)
>  		 */
>  		if (!machine->kptr_restrict_warned && !top->vmlinux_warned &&
> -		    __map__is_kernel(al.map) && map__has_symbols(al.map)) {
> +		    __map__is_kernel(al.map) && !map__has_symbols(al.map)) {
>  			if (symbol_conf.vmlinux_name) {
>  				char serr[256];
>  
> -- 
> 2.47.0
>