[PATCH -next 1/2] perf stat: Increase perf_attr_map entries

[Tengda Wu]

bperf restricts the size of perf_attr_map's entries to 16, which
cannot hold all events in many scenarios. A typical example is
when the user specifies `-a -ddd` ([0]). And in other cases such as
top-down analysis, which often requires a set of more than 16 PMUs
to be collected simultaneously.

Fix this by increase perf_attr_map entries to 100, and an event
number check has been introduced when bperf__load() to ensure that
users receive a more friendly prompt when the event limit is reached.

  [0] https://lore.kernel.org/all/20230104064402.1551516-3-namhyung@xxxxxxxxxx/

Fixes: 7fac83aaf2ee ("perf stat: Introduce 'bperf' to share hardware PMCs with BPF")
Signed-off-by: Tengda Wu <wutengda@xxxxxxxxxxxxxxx>
---
 tools/perf/util/bpf_counter.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index 7a8af60e0f51..3346129c20cf 100644
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -28,7 +28,7 @@
 #include "bpf_skel/bperf_leader.skel.h"
 #include "bpf_skel/bperf_follower.skel.h"
 
-#define ATTR_MAP_SIZE 16
+#define ATTR_MAP_SIZE 100
 
 static inline void *u64_to_ptr(__u64 ptr)
 {
@@ -451,6 +451,12 @@ static int bperf__load(struct evsel *evsel, struct target *target)
 	enum bperf_filter_type filter_type;
 	__u32 filter_entry_cnt, i;
 
+	if (evsel->evlist->core.nr_entries > ATTR_MAP_SIZE) {
+		pr_err("Too many events, please limit to %d or less\n",
+			ATTR_MAP_SIZE);
+		return -1;
+	}
+
 	if (bperf_check_target(evsel, target, &filter_type, &filter_entry_cnt))
 		return -1;
 
-- 
2.34.1