Re: [PATCH net-next] sctp: move trace_sctp_probe_path into sctp_outq_sack

On Thu, Dec 26, 2019 at 03:38:35PM -0800, David Miller wrote:

From: Kevin Kou <redacted>
Date: Fri, 27 Dec 2019 07:09:07 +0800

quoted

quoted

From: Kevin Kou <redacted>
Date: Thu, 26 Dec 2019 12:29:17 +0000

quoted

This patch is to remove trace_sctp_probe_path from the TP_fast_assign
part of TRACE_EVENT(sctp_probe) to avoid the nest of entry function,
and trigger sctp_probe_path_trace in sctp_outq_sack.

...

Applied, but why did you remove the trace enabled check, just out of
curiosity?

Actually, the check in trace_sctp_probe_path_enabled also done in
trace_sctp_probe_path according to the Macro definition, both check
if (static_key_false(&__tracepoint_##name.key)).

Indeed, thanks for the explanation.

It was duplicated, yes, but it was also a small optimization:

if (enabled) {
  for (X times) {
    if (enabled) {
    }
  }
}

So it wouldn't traverse the list if not needed.  But X is usually 1 or
2 and this list is already traversed multiple times in this code path.