Also, note that bpf_trace_printk() is slow, and
should only be used for debugging purposes. For
this reason, a notice block (spanning several
lines) is printed to kernel logs and states that
the helper should not be used "for production use"
the first time this helper is used (or more
precisely, when trace_printk() buffers are
allocated). For passing values to user space, perf
events should be preferred.