linux-kernel - Re: [PATCH v3 04/20] perf arm-spe: Refactor arm_spe_get

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Message-ID: <fa476979-4c43-a247-7fb6-b77117575c20@arm.com>
Date:   Fri, 23 Oct 2020 18:09:20 +0100
From:   André Przywara <andre.przywara@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>, Al Grant <Al.Grant@....com>,
        Dave Martin <Dave.Martin@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 04/20] perf arm-spe: Refactor arm_spe_get_events()

On 22/10/2020 15:58, Leo Yan wrote:
> In function arm_spe_get_events(), the event packet's 'index' is assigned
> as payload length, but the flow is not directive: it firstly gets the
> packet length from the return value of arm_spe_get_payload(), the value
> includes header length (1) and payload length:
> 
>   int ret = arm_spe_get_payload(buf, len, packet);
> 
> and then reduces header length from packet length, so finally get the
> payload length:
> 
>   packet->index = ret - 1;
> 
> To simplify the code, this patch directly assigns payload length to
> event packet's index; and at the end it calls arm_spe_get_payload() to
> return the payload value.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>

Reviewed-by: Andre Przywara <andre.przywara@....com>

Cheers,
Andre

> ---
>  tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> index 4294c133a465..f3bb8bf102aa 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> @@ -136,8 +136,6 @@ static int arm_spe_get_timestamp(const unsigned char *buf, size_t len,
>  static int arm_spe_get_events(const unsigned char *buf, size_t len,
>  			      struct arm_spe_pkt *packet)
>  {
> -	int ret = arm_spe_get_payload(buf, len, packet);
> -
>  	packet->type = ARM_SPE_EVENTS;
>  
>  	/* we use index to identify Events with a less number of
> @@ -145,9 +143,9 @@ static int arm_spe_get_events(const unsigned char *buf, size_t len,
>  	 * LLC-REFILL, and REMOTE-ACCESS events are identified if
>  	 * index > 1.
>  	 */
> -	packet->index = ret - 1;
> +	packet->index = arm_spe_payload_len(buf[0]);
>  
> -	return ret;
> +	return arm_spe_get_payload(buf, len, packet);
>  }
>  
>  static int arm_spe_get_data_source(const unsigned char *buf, size_t len,
>