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Subject: Re: [PATCH v4 10/10] perf record: introduce --ctl-fd[-ack] options
To:     Alexey Budankov <alexey.budankov@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <653fe5f3-c986-a841-1ed8-0a7d2fa24c00@linux.intel.com>
 <cd791bc8-2609-a136-a833-1dab6df68ff2@linux.intel.com>
From:   Adrian Hunter <adrian.hunter@intel.com>
Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki,
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Message-ID: <b4b2ddb9-296b-c260-32ef-fee17e04a29d@intel.com>
Date:   Wed, 3 Jun 2020 15:05:07 +0300
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On 25/05/20 5:23 pm, Alexey Budankov wrote:
> 
> Introduce --ctl-fd[-ack] options to pass open file descriptors numbers
> from command line. Extend perf-record.txt file with --ctl-fd[-ack]
> options description. Document possible usage model introduced by
> --ctl-fd[-ack] options by providing example bash shell script.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
>  tools/perf/Documentation/perf-record.txt | 39 ++++++++++++++++++++++++
>  tools/perf/builtin-record.c              | 10 ++++++
>  tools/perf/util/record.h                 |  2 ++
>  3 files changed, 51 insertions(+)
> 
> diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
> index c2c4ce7ccee2..5c012cfe68a4 100644
> --- a/tools/perf/Documentation/perf-record.txt
> +++ b/tools/perf/Documentation/perf-record.txt
> @@ -614,6 +614,45 @@ appended unit character - B/K/M/G
>  	The number of threads to run when synthesizing events for existing processes.
>  	By default, the number of threads equals 1.
>  
> +--ctl-fd::
> +--ctl-fd-ack::
> +Listen on ctl-fd descriptor for command to control measurement ('enable': enable events,
> +'disable': disable events. Optionally send control command completion ('ack') to fd-ack
> +descriptor to synchronize with the controlling process. 

You should also explain the use of --delay=-1 here.

Example of bash shell script
> +to enable and disable events during measurements:
> +
> +#!/bin/bash
> +
> +ctl_dir=/tmp/
> +
> +ctl_fifo=${ctl_dir}perf_ctl.fifo
> +test -p ${ctl_fifo} && unlink ${ctl_fifo}
> +mkfifo ${ctl_fifo}
> +exec {ctl_fd}<>${ctl_fifo}
> +
> +ctl_ack_fifo=${ctl_dir}perf_ctl_ack.fifo
> +test -p ${ctl_ack_fifo} && unlink ${ctl_ack_fifo}
> +mkfifo ${ctl_ack_fifo}
> +exec {ctl_fd_ack}<>${ctl_ack_fifo}
> +
> +perf record -D -1 -e cpu-cycles -a                        \
> +            --ctl-fd ${ctl_fd} --ctl-fd-ack ${ctl_fd_ack} \
> +            -- sleep 30 &
> +perf_pid=$!
> +
> +sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e1 && echo "enabled(${e1})"
> +sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d1 && echo "disabled(${d1})"
> +
> +exec {ctl_fd_ack}>&-
> +unlink ${ctl_ack_fifo}
> +
> +exec {ctl_fd}>&-
> +unlink ${ctl_fifo}
> +
> +wait -n ${perf_pid}
> +exit $?
> +
> +
>  SEE ALSO
>  --------
>  linkperf:perf-stat[1], linkperf:perf-list[1], linkperf:perf-intel-pt[1]
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 1ff3b7a77283..e057a2be42b7 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1761,6 +1761,9 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  		perf_evlist__start_workload(rec->evlist);
>  	}
>  
> +	if (evlist__initialize_ctlfd(rec->evlist, opts->ctl_fd, opts->ctl_fd_ack))
> +		goto out_child;
> +
>  	if (opts->initial_delay) {
>  		pr_info(EVLIST_DISABLED_MSG);
>  		if (opts->initial_delay > 0) {
> @@ -1907,6 +1910,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>  		record__synthesize_workload(rec, true);
>  
>  out_child:
> +	evlist__finalize_ctlfd(rec->evlist);
>  	record__mmap_read_all(rec, true);
>  	record__aio_mmap_read_sync(rec);
>  
> @@ -2392,6 +2396,8 @@ static struct record record = {
>  		},
>  		.mmap_flush          = MMAP_FLUSH_DEFAULT,
>  		.nr_threads_synthesize = 1,
> +		.ctl_fd              = -1,
> +		.ctl_fd_ack          = -1,
>  	},
>  	.tool = {
>  		.sample		= process_sample_event,
> @@ -2587,6 +2593,10 @@ static struct option __record_options[] = {
>  	OPT_UINTEGER(0, "num-thread-synthesize",
>  		     &record.opts.nr_threads_synthesize,
>  		     "number of threads to run for event synthesis"),
> +	OPT_INTEGER(0, "ctl-fd", &record.opts.ctl_fd,
> +		    "Listen on fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events)"),
> +	OPT_INTEGER(0, "ctl-fd-ack", &record.opts.ctl_fd_ack,
> +		    "Send control command completion ('ack') to fd ack descriptor"),
>  	OPT_END()
>  };
>  
> diff --git a/tools/perf/util/record.h b/tools/perf/util/record.h
> index 96a73bbd8cd4..da18aeca3623 100644
> --- a/tools/perf/util/record.h
> +++ b/tools/perf/util/record.h
> @@ -69,6 +69,8 @@ struct record_opts {
>  	int	      mmap_flush;
>  	unsigned int  comp_level;
>  	unsigned int  nr_threads_synthesize;
> +	int	      ctl_fd;
> +	int	      ctl_fd_ack;
>  };
>  
>  extern const char * const *record_usage;
>