Re: [PATCH v2] uprobes: make trace_uprobe->nhit counter a per-CPU one

Oleg Nesterov
2024-08-13T14:50:17Z

On 08/09, Andrii Nakryiko wrote:
>
> @@ -815,13 +824,21 @@ static int probes_profile_seq_show(struct seq_file *m, void *v)
> {
> struct dyn_event *ev = v;
> struct trace_uprobe *tu;
> + unsigned long nhits;
> + int cpu;
>
> if (!is_trace_uprobe(ev))
> return 0;
>
> tu = to_trace_uprobe(ev);
> +
> + nhits = 0;
> + for_each_possible_cpu(cpu) {
> + nhits += READ_ONCE(*per_cpu_ptr(tu->nhits, cpu));

why not

nhits += per_cpu(*tu->nhits, cpu);

?

See for example per_cpu_sum() or nr_processes(), per_cpu() should work just fine...

Other than that

Reviewed-by: Oleg Nesterov <oleg@redhat.com>