Re: [PATCH] perf record: Add an option to take an AUX snapshot on exit

[Alexander Shishkin]

Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx> writes:

> It is sometimes useful to generate a snapshot when perf record exits;
> I've been using a wrapper script around the workload that would do a
> killall -USR2 perf when the workload exits.
>
> This patch makes it easier and also works when perf record is attached
> to a pre-existing task. A new snapshot option 'e' can be specified in
> -S to enable this behavior:
>
> root@elsewhere:~# perf record -e intel_pt// -Se sleep 1
> [ perf record: Woken up 2 times to write data ]
> [ perf record: Captured and wrote 0.085 MB perf.data ]
>
> Signed-off-by: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
> ---
>  tools/perf/Documentation/perf-record.txt | 11 ++++++++---
>  tools/perf/builtin-record.c              |  4 ++++
>  tools/perf/perf.h                        |  1 +
>  tools/perf/util/auxtrace.c               | 10 ++++++++++
>  4 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index ea3789d05e..164ffce680 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -387,9 +387,14 @@ CLOCK_BOOTTIME, CLOCK_REALTIME and CLOCK_TAI.
>  -S::
>  --snapshot::
>  Select AUX area tracing Snapshot Mode. This option is valid only with an
> -AUX area tracing event. Optionally the number of bytes to capture per
> -snapshot can be specified. In Snapshot Mode, trace data is captured only when
> -signal SIGUSR2 is received.
> +AUX area tracing event. Optionally, certain snapshot capturing parameters
> +can be specified in a string that follows this option:
> +  'e': take one last snapshot on exit; guarantees that there is at least one
> +       snapshot in the output file;
> +  <size>: if the PMU supports this, specify the desired snapshot size.
> +
> +In Snapshot Mode trace data is captured only when signal SIGUSR2 is received
> +and on exit if the above 'e' option is given.
>  
>  --proc-map-timeout::
>  When processing pre-existing threads /proc/XXX/mmap, it may take a long time,
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 70340ff200..42d1b7aeee 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1136,6 +1136,10 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  			disabled = true;
>  		}
>  	}
> +
> +	if (opts->auxtrace_snapshot_on_exit)
> +		record__read_auxtrace_snapshot(rec);
> +
>  	trigger_off(&auxtrace_snapshot_trigger);
>  	trigger_off(&switch_output_trigger);
>  
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 806c216a10..b79c57485b 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -50,6 +50,7 @@ struct record_opts {
>  	bool	     running_time;
>  	bool	     full_auxtrace;
>  	bool	     auxtrace_snapshot_mode;
> +	bool	     auxtrace_snapshot_on_exit;
>  	bool	     record_namespaces;
>  	bool	     record_switch_events;
>  	bool	     all_kernel;
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index 0daf63b9ee..25ad4445b0 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -564,6 +564,16 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
>  	if (!str)
>  		return 0;
>  
> +	/* PMU-agnostic options */
> +	switch (*str) {
> +	case 'e':
> +		opts->auxtrace_snapshot_on_exit = true;
> +		str++;
> +		break;
> +	default:
> +		break;
> +	}
> +
>  	if (itr)
>  		return itr->parse_snapshot_options(itr, opts, str);
>  
> -- 
> 2.11.0