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@kernel.org>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>
Cc: bpf@vger.kernel.org
Link: https://lore.kernel.org/r/20230406210611.1622492-2-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

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).

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;

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 {

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).