[PATCH v3 1/2] perf pmu: Make pmu_alias_terms weak again

[PATCH v3 1/2] perf pmu: Make pmu_alias_terms weak again

[Ian Rogers]

The terms for a json event should be weak so they don't override
command line options.

Before:
```
$ perf record -vv -c 1000 -e uops_issued.any -o /dev/null true 2>&1
|grep "{ sample_period, sample_freq }"
 { sample_period, sample_freq }   200003
 { sample_period, sample_freq }   2000003
 { sample_period, sample_freq }   1000
```

After:
```
$ perf record -vv -c 1000 -e uops_issued.any -o /dev/null true 2>&1
|grep "{ sample_period, sample_freq }"
 { sample_period, sample_freq }   1000
 { sample_period, sample_freq }   1000
 { sample_period, sample_freq }   1000
```

Fixes: 84bae3af20d0 ("perf pmu: Don't eagerly parse event terms")
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/pmu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index d597263fab4f..f14f2a12d061 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -802,6 +802,7 @@ static int pmu_aliases_parse_eager(struct perf_pmu *pmu, int sysfs_fd)
 static int pmu_alias_terms(struct perf_pmu_alias *alias, struct list_head *terms)
 {
 	struct parse_events_terms alias_terms;
+	struct parse_events_term *term;
 	int ret;
 
 	parse_events_terms__init(&alias_terms);
@@ -812,6 +813,13 @@ static int pmu_alias_terms(struct perf_pmu_alias *alias, struct list_head *terms
 		parse_events_terms__exit(&alias_terms);
 		return ret;
 	}
+	list_for_each_entry(term, &alias_terms.terms, list) {
+		/*
+		 * Weak terms don't override command line options,
+		 * which we don't want for implicit terms in aliases.
+		 */
+		term->weak = true;
+	}
 	list_splice_init(&alias_terms.terms, terms);
 	parse_events_terms__exit(&alias_terms);
 	return 0;
-- 
2.51.2.1041.gc1ab5b90ca-goog

[PATCH v3 2/2] perf test: Add test that command line period overrides sysfs/json values

[Ian Rogers]

The behavior of weak terms is subtle, add a test that they aren't
accidentally broken. The test finds an event with a weak 'period' and
then overrides it. In no such event is present then the test skips.

Signed-off-by: Ian Rogers <irogers@google.com>
---
v3: Add workaround in case the raw event is matched (Namhyung).
v2: Add more comments to the test code and reduce the line length (Namhyung).
---
 tools/perf/tests/shell/record_weak_term.sh | 37 ++++++++++++++++++++++
 1 file changed, 37 insertions(+)
 create mode 100755 tools/perf/tests/shell/record_weak_term.sh

diff --git a/tools/perf/tests/shell/record_weak_term.sh b/tools/perf/tests/shell/record_weak_term.sh
new file mode 100755
index 000000000000..811b00ffb47a
--- /dev/null
+++ b/tools/perf/tests/shell/record_weak_term.sh
@@ -0,0 +1,37 @@
+#!/bin/bash
+# record weak terms
+# SPDX-License-Identifier: GPL-2.0
+# Test that command line options override weak terms from sysfs or inbuilt json.
+set -e
+
+shelldir=$(dirname "$0")
+# shellcheck source=lib/setup_python.sh
+. "${shelldir}"/lib/setup_python.sh
+
+# Find the first event with a specified period, such as
+# "cpu_core/event=0x24,period=200003,umask=0xff/"
+event=$(perf list --json | $PYTHON -c '
+import json, sys
+for e in json.load(sys.stdin):
+    if "EventName" not in e or "/modifier" in e["EventName"]:
+        continue
+    if "Encoding" in e and "period=" in e["Encoding"]:
+        print(e["EventName"])
+        break
+')
+if [[ "$event" = "" ]]
+then
+  echo "Skip: No sysfs/json events with inbuilt period."
+  exit 2
+fi
+
+echo "Testing that for $event the period is overridden with 1000"
+perf list --detail "$event"
+if ! perf record -c 1000 -vv -e "$event" -o /dev/null true 2>&1 | \
+  grep -q -F '{ sample_period, sample_freq }   1000'
+then
+  echo "Fail: Unexpected verbose output and sample period"
+  exit 1
+fi
+echo "Success"
+exit 0
-- 
2.51.2.1041.gc1ab5b90ca-goog

Re: [PATCH v3 1/2] perf pmu: Make pmu_alias_terms weak again

[Namhyung Kim]

On Sat, 08 Nov 2025 16:59:58 -0800, Ian Rogers wrote:
> The terms for a json event should be weak so they don't override
> command line options.
> 
> Before:
> ```
> $ perf record -vv -c 1000 -e uops_issued.any -o /dev/null true 2>&1
> |grep "{ sample_period, sample_freq }"
>  { sample_period, sample_freq }   200003
>  { sample_period, sample_freq }   2000003
>  { sample_period, sample_freq }   1000
> ```
> 
> [...]
Applied to perf-tools-next, thanks!

Best regards,
Namhyung