linux-kernel - Re: [PATCH v6 3/8] perf cs-etm: Set sample flags for trace discontinuity

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Date:   Wed, 23 Jan 2019 14:04:35 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Robert Walker <robert.walker@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Coresight ML <coresight@...ts.linaro.org>
Subject: Re: [PATCH v6 3/8] perf cs-etm: Set sample flags for trace
 discontinuity

On Sat, Jan 19, 2019 at 09:43:42AM +0800, Leo Yan wrote:
> In the middle of trace stream, it might be interrupted thus the trace
> data is not continuous, the trace stream firstly is ended for previous
> trace block and restarted for next block.
> 
> To display related information for showing trace is restarted, this
> patch set sample flags for trace discontinuity:
> 
> - If one discontinuity packet is coming, append flag
>   PERF_IP_FLAG_TRACE_END to the previous packet to indicate the trace
>   has been ended;
> - If one instruction packet is following discontinuity packet, this
>   instruction packet is the first one packet to restarting trace.  So
>   set flag PERF_IP_FLAG_TRACE_START to discontinuity packet, this flag
>   will be used to generate sample when connect with the sequential
>   instruction packet.
> 
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  tools/perf/util/cs-etm.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index d05cac5295f1..1aa29633ce77 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -1111,6 +1111,7 @@ static int cs_etm__end_block(struct cs_etm_queue *etmq)
>  static int cs_etm__set_sample_flags(struct cs_etm_queue *etmq)
>  {
>  	struct cs_etm_packet *packet = etmq->packet;
> +	struct cs_etm_packet *prev_packet = etmq->prev_packet;
>  
>  	switch (packet->sample_type) {
>  	case CS_ETM_RANGE:
> @@ -1170,8 +1171,26 @@ static int cs_etm__set_sample_flags(struct cs_etm_queue *etmq)
>  		    packet->last_instr_subtype == OCSD_S_INSTR_V8_RET)
>  			packet->flags = PERF_IP_FLAG_BRANCH |
>  					PERF_IP_FLAG_RETURN;
> +
> +		/*
> +		 * Decoder might insert a discontinuity in the middle of
> +		 * instruction packets, fixup prev_packet with flag
> +		 * PERF_IP_FLAG_TRACE_BEGIN to indicate restarting trace.
> +		 */
> +		if (prev_packet->sample_type == CS_ETM_DISCONTINUITY)
> +			prev_packet->flags |= PERF_IP_FLAG_BRANCH |
> +					      PERF_IP_FLAG_TRACE_BEGIN;
>  		break;
>  	case CS_ETM_DISCONTINUITY:
> +		/*
> +		 * The trace is discontinuous, if the previous packet is
> +		 * instruction packet, set flag PERF_IP_FLAG_TRACE_END
> +		 * for previous packet.
> +		 */
> +		if (prev_packet->sample_type == CS_ETM_RANGE)
> +			prev_packet->flags |= PERF_IP_FLAG_BRANCH |
> +					      PERF_IP_FLAG_TRACE_END;
> +		break;
>  	case CS_ETM_EXCEPTION:
>  	case CS_ETM_EXCEPTION_RET:
>  	case CS_ETM_EMPTY:

Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>

> -- 
> 2.17.1
>