Re: [PATCH v7 2/2] perf cs-etm: Split --dump-raw-trace by AUX records

[Leo Yan]

Hi James,

On Thu, Jun 24, 2021 at 05:43:03PM +0100, James Clark wrote:
> Currently --dump-raw-trace skips queueing and splitting buffers because
> of an early exit condition in cs_etm__process_auxtrace_info(). Once
> that is removed we can print the split data by using the queues
> and searching for split buffers with the same reference as the
> one that is currently being processed.
> 
> This keeps the same behaviour of dumping in file order when an AUXTRACE
> event appears, rather than moving trace dump to where AUX records are in
> the file.
> 
> There will be a newline and size printout for each fragment. For example
> this buffer is comprised of two AUX records, but was printed as one:
> 
>   0 0 0x8098 [0x30]: PERF_RECORD_AUXTRACE size: 0xa0  offset: 0  ref: 0x491a4dfc52fc0e6e  idx: 0  t
> 
>   . ... CoreSight ETM Trace data: size 160 bytes
>           Idx:0; ID:10;   I_ASYNC : Alignment Synchronisation.
>           Idx:12; ID:10;  I_TRACE_INFO : Trace Info.; INFO=0x0 { CC.0 }
>           Idx:17; ID:10;  I_ADDR_L_64IS0 : Address, Long, 64 bit, IS0.; Addr=0x0000000000000000;
>           Idx:80; ID:10;  I_ASYNC : Alignment Synchronisation.
>           Idx:92; ID:10;  I_TRACE_INFO : Trace Info.; INFO=0x0 { CC.0 }
>           Idx:97; ID:10;  I_ADDR_L_64IS0 : Address, Long, 64 bit, IS0.; Addr=0xFFFFDE2AD3FD76D4;
> 
> But is now printed as two fragments:
> 
>   0 0 0x8098 [0x30]: PERF_RECORD_AUXTRACE size: 0xa0  offset: 0  ref: 0x491a4dfc52fc0e6e  idx: 0  t
> 
>   . ... CoreSight ETM Trace data: size 80 bytes
>           Idx:0; ID:10;   I_ASYNC : Alignment Synchronisation.
>           Idx:12; ID:10;  I_TRACE_INFO : Trace Info.; INFO=0x0 { CC.0 }
>           Idx:17; ID:10;  I_ADDR_L_64IS0 : Address, Long, 64 bit, IS0.; Addr=0x0000000000000000;
> 
>   . ... CoreSight ETM Trace data: size 80 bytes
>           Idx:80; ID:10;  I_ASYNC : Alignment Synchronisation.
>           Idx:92; ID:10;  I_TRACE_INFO : Trace Info.; INFO=0x0 { CC.0 }
>           Idx:97; ID:10;  I_ADDR_L_64IS0 : Address, Long, 64 bit, IS0.; Addr=0xFFFFDE2AD3FD76D4;
> 
> Decoding errors that appeared in problematic files are now not present,
> for example:
> 
>         Idx:808; ID:1c; I_BAD_SEQUENCE : Invalid Sequence in packet.[I_ASYNC]
>         ...
>         PKTP_ETMV4I_0016 : 0x0014 (OCSD_ERR_INVALID_PCKT_HDR) [Invalid packet header]; TrcIdx=822
> 
> Signed-off-by: James Clark <james.clark@xxxxxxx>

I tested this patch and the result looks good for me.

I found a side effect introduced by this change is the perf raw dump
also synthesizes events PERF_RECORD_ATTR.  This is because function
cs_etm__synth_events() will execute after applying this patch and it
synthesizes PERF_RECORD_ATTR events.  I don't see any harm for this,
so:

Tested-by: Leo Yan <leo.yan@xxxxxxxxxx>

Please see an extra comment in below.

> ---
>  tools/perf/util/cs-etm.c | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 88e8122f73c9..ad777c2a342f 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -2430,6 +2430,22 @@ static int cs_etm__process_event(struct perf_session *session,
>  	return 0;
>  }
>  
> +static void dump_queued_data(struct cs_etm_auxtrace *etm,
> +			     struct perf_record_auxtrace *event)
> +{
> +	struct auxtrace_buffer *buf;
> +	unsigned int i;
> +	/*
> +	 * Find all buffers with same reference in the queues and dump them.
> +	 * This is because the queues can contain multiple entries of the same
> +	 * buffer that were split on aux records.
> +	 */
> +	for (i = 0; i < etm->queues.nr_queues; ++i)
> +		list_for_each_entry(buf, &etm->queues.queue_array[i].head, list)
> +			if (buf->reference == event->reference)
> +				cs_etm__dump_event(etm, buf);
> +}
> +
>  static int cs_etm__process_auxtrace_event(struct perf_session *session,
>  					  union perf_event *event,
>  					  struct perf_tool *tool __maybe_unused)
> @@ -2462,7 +2478,8 @@ static int cs_etm__process_auxtrace_event(struct perf_session *session,
>  				cs_etm__dump_event(etm, buffer);
>  				auxtrace_buffer__put_data(buffer);
>  			}
> -	}
> +	} else if (dump_trace)
> +		dump_queued_data(etm, &event->auxtrace);

IIUC, in the function cs_etm__process_auxtrace_event(), since
"etm->data_queued" is always true, below flow will never run:

    if (!etm->data_queued) {
        ......

        if (dump_trace)
            if (auxtrace_buffer__get_data(buffer, fd)) {
                    cs_etm__dump_event(etm, buffer);
                    auxtrace_buffer__put_data(buffer);
            }
    }

If so, it's better to use a new patch to polish the code.

Thanks,
Leo

>  
>  	return 0;
>  }
> @@ -3038,7 +3055,6 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
>  
>  	if (dump_trace) {
>  		cs_etm__print_auxtrace_info(auxtrace_info->priv, num_cpu);
> -		return 0;
>  	}
>  
>  	err = cs_etm__synth_events(etm, session);
> -- 
> 2.28.0
>