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

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Date:   Fri, 27 Dec 2019 10:33:07 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Kevin Kou <qdkevin.kou@...il.com>
Cc:     linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        nhorman@...driver.com, davem@...emloft.net
Subject: Re: [PATCH net-next] sctp: add enabled check for path tracepoint
 loop.

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@...il.com>

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