[PATCH net-next] sctp: add enabled check for path tracepoint loop.

[PATCH net-next] sctp: add enabled check for path tracepoint loop.

[Kevin Kou]

sctp_outq_sack is the main function handles SACK, it is called very
frequently. As the commit "move trace_sctp_probe_path into sctp_outq_sack"
added below code to this function, sctp tracepoint is disabled most of time,
but the loop of transport list will be always called even though the
tracepoint is disabled, this is unnecessary.

+	/* SCTP path tracepoint for congestion control debugging. */
+	list_for_each_entry(transport, transport_list, transports) {
+		trace_sctp_probe_path(transport, asoc);
+	}

This patch is to add tracepoint enabled check at outside of the loop of
transport list, and avoid traversing the loop when trace is disabled,
it is a small optimization.

Signed-off-by: Kevin Kou <qdkevin.kou@gmail.com>
---
 net/sctp/outqueue.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
index adceb22..83ddcfe 100644
--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -1240,8 +1240,9 @@ int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
 	transport_list = &asoc->peer.transport_addr_list;
 
 	/* SCTP path tracepoint for congestion control debugging. */
-	list_for_each_entry(transport, transport_list, transports) {
-		trace_sctp_probe_path(transport, asoc);
+	if (trace_sctp_probe_path_enabled()) {
+		list_for_each_entry(transport, transport_list, transports)
+			trace_sctp_probe_path(transport, asoc);
 	}
 
 	sack_ctsn = ntohl(sack->cum_tsn_ack);
-- 
1.8.3.1

Re: [PATCH net-next] sctp: add enabled check for path tracepoint loop.

[Marcelo Ricardo Leitner]

On Fri, Dec 27, 2019 at 01:11:16PM +0000, Kevin Kou wrote:
> sctp_outq_sack is the main function handles SACK, it is called very
> frequently. As the commit "move trace_sctp_probe_path into sctp_outq_sack"
> added below code to this function, sctp tracepoint is disabled most of time,
> but the loop of transport list will be always called even though the
> tracepoint is disabled, this is unnecessary.
> 
> +	/* SCTP path tracepoint for congestion control debugging. */
> +	list_for_each_entry(transport, transport_list, transports) {
> +		trace_sctp_probe_path(transport, asoc);
> +	}
> 
> This patch is to add tracepoint enabled check at outside of the loop of
> transport list, and avoid traversing the loop when trace is disabled,
> it is a small optimization.
> 
> Signed-off-by: Kevin Kou <qdkevin.kou@gmail.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Thanks Kevin.

Btw, I'm out for PTOs for the next 2 weeks. Probably won't be
reviewing patches during that.

> ---
>  net/sctp/outqueue.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sctp/outqueue.c b/net/sctp/outqueue.c
> index adceb22..83ddcfe 100644
> --- a/net/sctp/outqueue.c
> +++ b/net/sctp/outqueue.c
> @@ -1240,8 +1240,9 @@ int sctp_outq_sack(struct sctp_outq *q, struct sctp_chunk *chunk)
>  	transport_list = &asoc->peer.transport_addr_list;
>  
>  	/* SCTP path tracepoint for congestion control debugging. */
> -	list_for_each_entry(transport, transport_list, transports) {
> -		trace_sctp_probe_path(transport, asoc);
> +	if (trace_sctp_probe_path_enabled()) {
> +		list_for_each_entry(transport, transport_list, transports)
> +			trace_sctp_probe_path(transport, asoc);
>  	}
>  
>  	sack_ctsn = ntohl(sack->cum_tsn_ack);
> -- 
> 1.8.3.1
>