linux-kernel - [PATCH 1/5] perf stat: Constify control data for BPF

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Message-ID: <20240902200515.2103769-2-namhyung@kernel.org>
Date: Mon,  2 Sep 2024 13:05:11 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org,
	Song Liu <song@...nel.org>,
	bpf@...r.kernel.org
Subject: [PATCH 1/5] perf stat: Constify control data for BPF

The control knobs set before loading BPF programs should be declared as
'const volatile' so that it can be optimized by the BPF core.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/bpf_counter_cgroup.c        | 6 +++---
 tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf_counter_cgroup.c b/tools/perf/util/bpf_counter_cgroup.c
index ea29c372f339705d..6ff42619de12bddf 100644
--- a/tools/perf/util/bpf_counter_cgroup.c
+++ b/tools/perf/util/bpf_counter_cgroup.c
@@ -61,6 +61,9 @@ static int bperf_load_program(struct evlist *evlist)
 	skel->rodata->num_cpus = total_cpus;
 	skel->rodata->num_events = evlist->core.nr_entries / nr_cgroups;
 
+	if (cgroup_is_v2("perf_event") > 0)
+		skel->rodata->use_cgroup_v2 = 1;
+
 	BUG_ON(evlist->core.nr_entries % nr_cgroups != 0);
 
 	/* we need one copy of events per cpu for reading */
@@ -82,9 +85,6 @@ static int bperf_load_program(struct evlist *evlist)
 		goto out;
 	}
 
-	if (cgroup_is_v2("perf_event") > 0)
-		skel->bss->use_cgroup_v2 = 1;
-
 	err = -1;
 
 	cgrp_switch = evsel__new(&cgrp_switch_attr);
diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
index 6a438e0102c5a2cb..57cab7647a9ad766 100644
--- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
+++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
@@ -57,9 +57,9 @@ struct cgroup___old {
 
 const volatile __u32 num_events = 1;
 const volatile __u32 num_cpus = 1;
+const volatile int use_cgroup_v2 = 0;
 
 int enabled = 0;
-int use_cgroup_v2 = 0;
 int perf_subsys_id = -1;
 
 static inline __u64 get_cgroup_v1_ancestor_id(struct cgroup *cgrp, int level)
-- 
2.46.0.469.g59c65b2a67-goog