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perf pmu: Skip test on Arm64 when #slots is zero

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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 3a61fd866e ("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: 3a61fd866e ("perf expr: Return -EINVAL for syntax error in expr__find_ids()")
Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Leo Yan 2026-04-10 12:13:44 +01:00 • committed by Arnaldo Carvalho de Melo
commit 2e2ba7d1ea
1 changed files with 22 additions and 2 deletions
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