Re: [PATCH bpf-next 4/4] selftests/bpf: Allow to benchmark trigger with stacktrace

On Thu, Jan 15, 2026 at 10:48 AM Andrii Nakryiko
[off-list ref] wrote:

On Mon, Jan 12, 2026 at 1:50 PM Jiri Olsa [off-list ref] wrote:

quoted

Adding support to call bpf_get_stackid helper from trigger programs,
so far added for kprobe multi.

Adding the --stacktrace/-g option to enable it.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/testing/selftests/bpf/bench.c            |  4 ++++
 tools/testing/selftests/bpf/bench.h            |  1 +
 .../selftests/bpf/benchs/bench_trigger.c       |  1 +
 .../selftests/bpf/progs/trigger_bench.c        | 18 ++++++++++++++++++
 4 files changed, 24 insertions(+)

This now actually becomes a stack trace benchmark :) But I don't mind,
I think it would be good to be able to benchmark this. But I think we
should then implement it for all different tracing programs (tp,
raw_tp, fentry/fexit/fmod_ret) for consistency and so we can compare
and contrast?...

quoted

diff --git a/tools/testing/selftests/bpf/bench.c b/tools/testing/selftests/bpf/bench.c
index bd29bb2e6cb5..8dadd9c928ec 100644
--- a/tools/testing/selftests/bpf/bench.c
+++ b/tools/testing/selftests/bpf/bench.c

@@ -265,6 +265,7 @@ static const struct argp_option opts[] = {
        { "verbose", 'v', NULL, 0, "Verbose debug output"},
        { "affinity", 'a', NULL, 0, "Set consumer/producer thread affinity"},
        { "quiet", 'q', NULL, 0, "Be more quiet"},
+       { "stacktrace", 'g', NULL, 0, "Get stack trace"},

bikeshedding time: why "g"? why not -S or something like that?

quoted

        { "prod-affinity", ARG_PROD_AFFINITY_SET, "CPUSET", 0,
          "Set of CPUs for producer threads; implies --affinity"},
        { "cons-affinity", ARG_CONS_AFFINITY_SET, "CPUSET", 0,

@@ -350,6 +351,9 @@ static error_t parse_arg(int key, char *arg, struct argp_state *state)
        case 'q':
                env.quiet = true;
                break;
+       case 'g':
+               env.stacktrace = true;
+               break;
        case ARG_PROD_AFFINITY_SET:
                env.affinity = true;
                if (parse_num_list(arg, &env.prod_cpus.cpus,

diff --git a/tools/testing/selftests/bpf/bench.h b/tools/testing/selftests/bpf/bench.h
index bea323820ffb..7cf21936e7ed 100644
--- a/tools/testing/selftests/bpf/bench.h
+++ b/tools/testing/selftests/bpf/bench.h

@@ -26,6 +26,7 @@ struct env {
        bool list;
        bool affinity;
        bool quiet;
+       bool stacktrace;
        int consumer_cnt;
        int producer_cnt;
        int nr_cpus;

diff --git a/tools/testing/selftests/bpf/benchs/bench_trigger.c b/tools/testing/selftests/bpf/benchs/bench_trigger.c
index 34018fc3927f..aeec9edd3851 100644
--- a/tools/testing/selftests/bpf/benchs/bench_trigger.c
+++ b/tools/testing/selftests/bpf/benchs/bench_trigger.c

@@ -146,6 +146,7 @@ static void setup_ctx(void)
        bpf_program__set_autoload(ctx.skel->progs.trigger_driver, true);

        ctx.skel->rodata->batch_iters = args.batch_iters;
+       ctx.skel->rodata->stacktrace = env.stacktrace;
 }

 static void load_ctx(void)

diff --git a/tools/testing/selftests/bpf/progs/trigger_bench.c b/tools/testing/selftests/bpf/progs/trigger_bench.c
index 2898b3749d07..479400d96fa4 100644
--- a/tools/testing/selftests/bpf/progs/trigger_bench.c
+++ b/tools/testing/selftests/bpf/progs/trigger_bench.c

@@ -25,6 +25,23 @@ static __always_inline void inc_counter(void)
        __sync_add_and_fetch(&hits[cpu & CPU_MASK].value, 1);
 }

+volatile const int stacktrace;
+
+typedef __u64 stack_trace_t[128];
+
+struct {
+       __uint(type, BPF_MAP_TYPE_STACK_TRACE);
+       __uint(max_entries, 16384);
+       __type(key, __u32);
+       __type(value, stack_trace_t);
+} stackmap SEC(".maps");

oh, and why bother with STACK_TRACE map, just call bpf_get_stack() API
and have maybe per-CPU scratch array for stack trace (per-CPU so that
in multi-cpu benchmarks they don't just contend on the same cache
lines)

quoted

+
+static __always_inline void do_stacktrace(void *ctx)
+{
+       if (stacktrace)
+               bpf_get_stackid(ctx, &stackmap, 0);
+}
+
 SEC("?uprobe")
 int bench_trigger_uprobe(void *ctx)
 {

@@ -96,6 +113,7 @@ SEC("?kprobe.multi/bpf_get_numa_node_id")
 int bench_trigger_kprobe_multi(void *ctx)
 {
        inc_counter();
+       do_stacktrace(ctx);
        return 0;
 }

--

2.52.0