linux-kernel - [PATCH 3/7] perf lock contention: Update default map size to 16384

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Date:   Thu,  6 Apr 2023 14:06:07 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>
Cc:     Ian Rogers <irogers@...gle.com>,
        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>,
        Hao Luo <haoluo@...gle.com>, bpf@...r.kernel.org,
        Juri Lelli <juri.lelli@...hat.com>
Subject: [PATCH 3/7] perf lock contention: Update default map size to 16384

The BPF hash map will align the map size to a power of 2.  So 10k would
be 16k anyway.  Let's have the actual size to avoid confusions.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/Documentation/perf-lock.txt         | 3 ++-
 tools/perf/builtin-lock.c                      | 2 +-
 tools/perf/util/bpf_skel/lock_contention.bpf.c | 5 +----
 tools/perf/util/bpf_skel/lock_data.h           | 3 +++
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/tools/perf/Documentation/perf-lock.txt b/tools/perf/Documentation/perf-lock.txt
index b5e5d088d51c..6e5ba3cd2b72 100644
--- a/tools/perf/Documentation/perf-lock.txt
+++ b/tools/perf/Documentation/perf-lock.txt
@@ -157,7 +157,8 @@ CONTENTION OPTIONS
 
 -M::
 --map-nr-entries=<value>::
-	Maximum number of BPF map entries (default: 10240).
+	Maximum number of BPF map entries (default: 16384).
+	This will be aligned to a power of 2.
 
 --max-stack=<value>::
 	Maximum stack depth when collecting lock contention (default: 8).
diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
index ef56bf90058d..9b92c7a5aefb 100644
--- a/tools/perf/builtin-lock.c
+++ b/tools/perf/builtin-lock.c
@@ -60,7 +60,7 @@ static bool show_thread_stats;
 static bool show_lock_addrs;
 static bool show_lock_owner;
 static bool use_bpf;
-static unsigned long bpf_map_entries = 10240;
+static unsigned long bpf_map_entries = MAX_ENTRIES;
 static int max_stack_depth = CONTENTION_STACK_DEPTH;
 static int stack_skip = CONTENTION_STACK_SKIP;
 static int print_nr_entries = INT_MAX / 2;
diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 3f4ee3992e81..f9d2d792ccc8 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -7,9 +7,6 @@
 
 #include "lock_data.h"
 
-/* default buffer size */
-#define MAX_ENTRIES  10240
-
 /* for collect_lock_syms().  4096 was rejected by the verifier */
 #define MAX_CPUS  1024
 
@@ -63,7 +60,7 @@ struct {
 	__uint(type, BPF_MAP_TYPE_HASH);
 	__uint(key_size, sizeof(__u64));
 	__uint(value_size, sizeof(__u32));
-	__uint(max_entries, 16384);
+	__uint(max_entries, MAX_ENTRIES);
 } lock_syms SEC(".maps");
 
 struct {
diff --git a/tools/perf/util/bpf_skel/lock_data.h b/tools/perf/util/bpf_skel/lock_data.h
index 1ba61cb4d480..260062a9f2ab 100644
--- a/tools/perf/util/bpf_skel/lock_data.h
+++ b/tools/perf/util/bpf_skel/lock_data.h
@@ -15,6 +15,9 @@ struct contention_task_data {
 	char comm[TASK_COMM_LEN];
 };
 
+/* default buffer size */
+#define MAX_ENTRIES  16384
+
 /*
  * Upper bits of the flags in the contention_data are used to identify
  * some well-known locks which do not have symbols (non-global locks).
-- 
2.40.0.577.gac1e443424-goog