perf stat bperf cgroup: Increase MAX_EVENTS from 32 to 1024

[PATCH v1] perf stat bperf cgroup: Increase MAX_EVENTS from 32 to 1024

Posted by Ian Rogers 3 months, 3 weeks ago

The MAX_EVENTS value ensured a counted loop presumably to satisfy the
BPF verifier. It is possible to go past 32 events when gathering
uncore events. Increase the amount to 1024 as that should provide some
amount of headroom.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
index 57cab7647a9a..18ab4d9b49ff 100644
--- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
+++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c
@@ -7,7 +7,7 @@
 #include <bpf/bpf_core_read.h>
 
 #define MAX_LEVELS  10  // max cgroup hierarchy level: arbitrary
-#define MAX_EVENTS  32  // max events per cgroup: arbitrary
+#define MAX_EVENTS  1024  // max events per cgroup: arbitrary
 
 // NOTE: many of map and global data will be modified before loading
 //       from the userspace (perf tool) using the skeleton helpers.
-- 
2.51.0.788.g6d19910ace-goog

Re: [PATCH v1] perf stat bperf cgroup: Increase MAX_EVENTS from 32 to 1024

Posted by Namhyung Kim 3 months, 2 weeks ago

On Thu, 16 Oct 2025 08:07:18 -0700, Ian Rogers wrote:

> The MAX_EVENTS value ensured a counted loop presumably to satisfy the
> BPF verifier. It is possible to go past 32 events when gathering
> uncore events. Increase the amount to 1024 as that should provide some
> amount of headroom.
> 
> 

Applied to perf-tools-next, thanks!

Best regards,
Namhyung