* Re: [PATCH v2] perf pmu: Skip test on Arm64 when #slots is zero
[not found] <20260410-perf_fix_pmu_metrics_test-v2-1-61826ab3ca8b@arm.com>
[not found] ` <98ddaa65-747a-4b3e-9f72-05b90fc4eadb@linaro.org>
@ 2026-05-13 13:10 ` Ian Rogers
2026-05-13 14:37 ` Leo Yan
1 sibling, 1 reply; 3+ messages in thread
From: Ian Rogers @ 2026-05-13 13:10 UTC (permalink / raw)
To: Leo Yan
Cc: Arnaldo Carvalho de Melo, Namhyung Kim, Mark Rutland,
Alexander Shishkin, Jiri Olsa, Adrian Hunter, James Clark,
linux-perf-users, linux-kernel
On Fri, Apr 10, 2026 at 4:13 AM Leo Yan <leo.yan@arm.com> wrote:
>
> Some Arm64 PMUs expose 'caps/slots' as 0 when the slot count is not
> implemented, tool_pmu__read_event() currently returns false for this,
> so metrics that reference #slots are reported as syntax error.
>
> Since the commit 3a61fd866ef9 ("perf expr: Return -EINVAL for syntax
> error in expr__find_ids()"), these syntax errors are populated as
> failures and make the PMU metric test fail:
>
> 9.3: Parsing of PMU event table metrics:
> --- start ---
> ...
>
> Found metric 'backend_bound'
> metric expr 100 * (stall_slot_backend / (#slots * cpu_cycles)) for backend_bound
> parsing metric: 100 * (stall_slot_backend / (#slots * cpu_cycles))
> Failure to read '#slots'
> literal: #slots = nan
> syntax error
> Fail to parse metric or group `backend_bound'
>
> ...
> ---- end(-1) ----
> 9.3: Parsing of PMU event table metrics : FAILED!
>
> This commit introduces a new function is_expected_broken_metric() to
> identify broken metrics, and treats metrics containing "#slots" as
> expected broken when #slots == 0 on Arm64 platforms.
>
> Fixes: 3a61fd866ef9 ("perf expr: Return -EINVAL for syntax error in expr__find_ids()")
> Signed-off-by: Leo Yan <leo.yan@arm.com>
We get this failure for these metrics on x86 when building perf with
JEVENTS_ARCH=all. Rather than expecting the parse failure perhaps we
should just always return true in tool_pmu__read_event:
https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/util/tool_pmu.c#n421
I guess the problem there is that when these metrics are broken (no
slots value) you can't distinguish this case from other valid cases.
Reviewed-by: Ian Rogers <irogers@google.com>
Thanks,
Ian
> ---
> Changes in v2:
> - Checked pm->metric_expr instead of pm->metric_name and removed the
> negation before strstr() suggested by sashiko.
> - Link to v1: https://lore.kernel.org/r/20260410-perf_fix_pmu_metrics_test-v1-1-18a5d80f71b6@arm.com
> ---
> tools/perf/tests/pmu-events.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
> index a997168621688007c85495e2d9f6f459c2471516..b1609a7e1d8c9427e6bf9500380e8aac6167c7fa 100644
> --- a/tools/perf/tests/pmu-events.c
> +++ b/tools/perf/tests/pmu-events.c
> @@ -15,6 +15,7 @@
> #include "util/expr.h"
> #include "util/hashmap.h"
> #include "util/parse-events.h"
> +#include "util/tool_pmu.h"
> #include "metricgroup.h"
> #include "stat.h"
>
> @@ -817,6 +818,26 @@ struct metric {
> struct metric_ref metric_ref;
> };
>
> +static bool is_expected_broken_metric(const struct pmu_metric *pm)
> +{
> + if (!strcmp(pm->metric_name, "M1") || !strcmp(pm->metric_name, "M2") ||
> + !strcmp(pm->metric_name, "M3"))
> + return true;
> +
> +#if defined(__aarch64__)
> + /*
> + * Arm64 platforms may return "#slots == 0", which is treated as a
> + * syntax error by the parser. Don't test these metrics when running
> + * on such platforms.
> + */
> + if (strstr(pm->metric_expr, "#slots") &&
> + !tool_pmu__cpu_slots_per_cycle())
> + return true;
> +#endif
> +
> + return false;
> +}
> +
> static int test__parsing_callback(const struct pmu_metric *pm,
> const struct pmu_metrics_table *table,
> void *data)
> @@ -852,8 +873,7 @@ static int test__parsing_callback(const struct pmu_metric *pm,
>
> err = metricgroup__parse_groups_test(evlist, table, pm->metric_name);
> if (err) {
> - if (!strcmp(pm->metric_name, "M1") || !strcmp(pm->metric_name, "M2") ||
> - !strcmp(pm->metric_name, "M3")) {
> + if (is_expected_broken_metric(pm)) {
> (*failures)--;
> pr_debug("Expected broken metric %s skipping\n", pm->metric_name);
> err = 0;
>
> ---
> base-commit: 4cf1f549bbcdfea9c20df52994bb342677472dcd
> change-id: 20260408-perf_fix_pmu_metrics_test-73c4dedc8585
>
> Best regards,
> --
> Leo Yan <leo.yan@arm.com>
>
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