linux-kernel - [PATCH v3 8/9] perf stat: Read tool events last

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251106071241.141234-9-irogers@google.com>
Date: Wed,  5 Nov 2025 23:12:39 -0800
From: Ian Rogers <irogers@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Dr. David Alan Gilbert" <linux@...blig.org>, Yang Li <yang.lee@...ux.alibaba.com>, 
	James Clark <james.clark@...aro.org>, Thomas Falcon <thomas.falcon@...el.com>, 
	Thomas Richter <tmricht@...ux.ibm.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>, 
	Dapeng Mi <dapeng1.mi@...ux.intel.com>
Subject: [PATCH v3 8/9] perf stat: Read tool events last

When reading a metric like memory bandwidth on multiple sockets, the
additional sockets will be on CPUS > 0. Because of the affinity
reading, the counters are read on CPU 0 along with the time, then the
later sockets are read. This can lead to the later sockets having a
bandwidth larger than is possible for the period of time. To avoid
this moving the reading of tool events to occur after all other events
are read.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/builtin-stat.c | 29 ++++++++++++++++++++++++++++-
 tools/perf/util/evlist.c  |  4 ----
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 5f31cd5bb03b..75ff08c5f0ed 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -373,6 +373,9 @@ static int read_counters_with_affinity(void)
 		if (evsel__is_bpf(counter))
 			continue;
 
+		if (evsel__is_tool(counter))
+			continue;
+
 		if (!counter->err)
 			counter->err = read_counter_cpu(counter, evlist_cpu_itr.cpu_map_idx);
 	}
@@ -396,6 +399,24 @@ static int read_bpf_map_counters(void)
 	return 0;
 }
 
+static int read_tool_counters(void)
+{
+	struct evsel *counter;
+
+	evlist__for_each_entry(evsel_list, counter) {
+		int idx;
+
+		if (!evsel__is_tool(counter))
+			continue;
+
+		perf_cpu_map__for_each_idx(idx, counter->core.cpus) {
+			if (!counter->err)
+				counter->err = read_counter_cpu(counter, idx);
+		}
+	}
+	return 0;
+}
+
 static int read_counters(void)
 {
 	int ret;
@@ -409,7 +430,13 @@ static int read_counters(void)
 		return ret;
 
 	// Read non-BPF and non-tool counters next.
-	return read_counters_with_affinity();
+	ret = read_counters_with_affinity();
+	if (ret)
+		return ret;
+
+	// Read the tool counters last. This way the duration_time counter
+	// should always be greater than any other counter's enabled time.
+	return read_tool_counters();
 }
 
 static void process_counters(void)
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index b6df81b8a236..fc3dae7cdfca 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -368,10 +368,6 @@ static bool evlist__use_affinity(struct evlist *evlist)
 	struct perf_cpu_map *used_cpus = NULL;
 	bool ret = false;
 
-	/*
-	 * With perf record core.user_requested_cpus is usually NULL.
-	 * Use the old method to handle this for now.
-	 */
 	if (!evlist->core.user_requested_cpus ||
 	    cpu_map__is_dummy(evlist->core.user_requested_cpus))
 		return false;
-- 
2.51.2.1041.gc1ab5b90ca-goog