Commit af954f76 authored by Namhyung Kim's avatar Namhyung Kim
Browse files

perf tools: Check fallback error and order 



The perf_event_open might fail due to various reasons, so blindly
reducing precise_ip level might not be the best way to deal with it.

It seems the kernel return -EOPNOTSUPP when PMU doesn't support the
given precise level.  Let's try again with the correct error code.

This caused a problem on AMD, as it stops on precise_ip of 2 for IBS but
user events with exclude_kernel=1 cannot make progress.  Let's add the
evsel__handle_error_quirks() to this case specially.  I plan to work on
the kernel side to improve this situation but it'd still need some
special handling for IBS.

Reviewed-by: default avatarJames Clark <james.clark@linaro.org>
Reviewed-by: default avatarRavi Bangoria <ravi.bangoria@amd.com>
Acked-by: default avatarKan Liang <kan.liang@linux.intel.com>
Cc: James Clark <james.clark@arm.com>
Cc: Atish Patra <atishp@atishpatra.org>
Cc: Mingwei Zhang <mizhang@google.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20241016062359.264929-8-namhyung@kernel.org


Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
parent 28398ce1

tools/perf/util/evsel.c

+29 −9
Original line number Diff line number Diff line
@@ -2143,9 +2143,9 @@ static void evsel__detect_missing_pmu_features(struct evsel *evsel) 


	/*

	 * Must probe features in the order they were added to the

	 * perf_event_attr interface.  These are PMU specific limitation

	 * so we can detect with the given hardware event and stop on the

	 * first one succeeded.

	 * perf_event_attr interface.  These are kernel core limitation but

	 * specific to PMUs with branch stack.  So we can detect with the given

	 * hardware event and stop on the first one succeeded.

	 */



	/* Please add new feature detection here. */
@@ -2409,6 +2409,25 @@ static bool evsel__detect_missing_features(struct evsel *evsel) 
	return false;

}



static bool evsel__handle_error_quirks(struct evsel *evsel, int error)

{

	/*

	 * AMD core PMU tries to forward events with precise_ip to IBS PMU

	 * implicitly.  But IBS PMU has more restrictions so it can fail with

	 * supported event attributes.  Let's forward it back to the core PMU

	 * by clearing precise_ip only if it's from precise_max (:P).

	 */

	if ((error == -EINVAL || error == -ENOENT) && x86__is_amd_cpu() &&

	    evsel->core.attr.precise_ip && evsel->precise_max) {

		evsel->core.attr.precise_ip = 0;

		pr_debug2_peo("removing precise_ip on AMD\n");

		display_attr(&evsel->core.attr);

		return true;

	}



	return false;

}



static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,

		struct perf_thread_map *threads,

		int start_cpu_map_idx, int end_cpu_map_idx)
@@ -2527,9 +2546,6 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 
	return 0;



try_fallback:

	if (evsel__precise_ip_fallback(evsel))

		goto retry_open;



	if (evsel__ignore_missing_thread(evsel, perf_cpu_map__nr(cpus),

					 idx, threads, thread, err)) {

		/* We just removed 1 thread, so lower the upper nthreads limit. */
@@ -2546,11 +2562,15 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus, 
	if (err == -EMFILE && rlimit__increase_nofile(&set_rlimit))

		goto retry_open;



	if (err != -EINVAL || idx > 0 || thread > 0)

		goto out_close;

	if (err == -EOPNOTSUPP && evsel__precise_ip_fallback(evsel))

		goto retry_open;



	if (evsel__detect_missing_features(evsel))

	if (err == -EINVAL && evsel__detect_missing_features(evsel))

		goto fallback_missing_features;



	if (evsel__handle_error_quirks(evsel, err))

		goto retry_open;



out_close:

	if (err)

		threads->err_thread = thread;