linux-kernel - Re: [PATCH v3 9/9] perf record: introduce --ctl-fd[-ack] options

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Date:   Wed, 20 May 2020 18:21:22 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 9/9] perf record: introduce --ctl-fd[-ack] options


On 20.05.2020 15:38, Jiri Olsa wrote:
> On Wed, May 13, 2020 at 11:05:08AM +0300, 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@...ux.intel.com>
>> ---
>>  tools/perf/Documentation/perf-record.txt | 39 ++++++++++++++++++++++++
>>  tools/perf/builtin-record.c              |  9 ++++++
>>  tools/perf/util/record.h                 |  2 ++
>>  3 files changed, 50 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. 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 72f388623364..218cfaafaf10 100644
>> --- a/tools/perf/builtin-record.c
>> +++ b/tools/perf/builtin-record.c
>> @@ -1713,6 +1713,8 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
>>  		perf_evlist__start_workload(rec->evlist);
>>  	}
>>  
>> +	evlist__initialize_ctlfd(rec->evlist, opts->ctl_fd, opts->ctl_fd_ack);
> 
> please check return value in here

Accepted in v4.

~Alexey