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Subject: Re: [PATCH v3 6/9] perf stat: introduce --ctl-fd[-ack] options
To:     Jiri Olsa <jolsa@redhat.com>
Cc:     Arnaldo Carvalho de Melo <acme@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: <eb38e9e5-754f-d410-1d9b-e26b702d51b7@linux.intel.com>
 <6b8f7e1f-f89c-2c96-95ac-2a128b365a81@linux.intel.com>
 <20200520123819.GE157452@krava>
From:   Alexey Budankov <alexey.budankov@linux.intel.com>
Organization: Intel Corp.
Message-ID: <7dcbbca7-b99e-025e-91b4-71c45e746a7b@linux.intel.com>
Date:   Wed, 20 May 2020 18:05:33 +0300
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On 20.05.2020 15:38, Jiri Olsa wrote:
> On Wed, May 13, 2020 at 11:03:03AM +0300, Alexey Budankov wrote:
>>
>> Introduce --ctl-fd[-ack] options to pass open file descriptors numbers
>> from command line. Extend perf-stat.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-stat.txt | 40 ++++++++++++++++++++++++++
>>  tools/perf/builtin-stat.c              | 10 +++++++
>>  tools/perf/util/stat.h                 |  2 ++
>>  3 files changed, 52 insertions(+)
>>
>> diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
>> index 3b91b30d7672..7f7a0019fbfc 100644
>> --- a/tools/perf/Documentation/perf-stat.txt
>> +++ b/tools/perf/Documentation/perf-stat.txt
>> @@ -164,6 +164,46 @@ with it.  --append may be used here.  Examples:
>>       3>results  perf stat --log-fd 3          -- $cmd
>>       3>>results perf stat --log-fd 3 --append -- $cmd
>>  
>> +--ctl-fd::
>> +--ctl-fd-ack::
>> +
>> +Listen on ctl-fd descriptor for command to control measurement ('enable': enable events,
>> +'disable': disable events). Optionally send control command completion ('ack') to fd-ack
>> +descriptor to synchronize with the controlling process. Example of bash shell script
>> +to enable and disable events during measurements:
>> +
>> +#!/bin/bash
>> +
>> +ctl_dir=/tmp/
>> +
>> +ctl_fifo=${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 stat -D -1 -e cpu-cycles -a -I 1000                \
>> +          --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 $?
>> +
>> +
>>  --pre::
>>  --post::
>>  	Pre and post measurement hooks, e.g.:
>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
>> index abea82a1ba24..88055aaf670f 100644
>> --- a/tools/perf/builtin-stat.c
>> +++ b/tools/perf/builtin-stat.c
>> @@ -187,6 +187,8 @@ static struct perf_stat_config stat_config = {
>>  	.metric_only_len	= METRIC_ONLY_LEN,
>>  	.walltime_nsecs_stats	= &walltime_nsecs_stats,
>>  	.big_num		= true,
>> +	.ctl_fd			= -1,
>> +	.ctl_fd_ack		= -1
>>  };
>>  
>>  static inline void diff_timespec(struct timespec *r, struct timespec *a,
>> @@ -984,6 +986,10 @@ static struct option stat_options[] = {
>>  		    "Use with 'percore' event qualifier to show the event "
>>  		    "counts of one hardware thread by sum up total hardware "
>>  		    "threads of same physical core"),
>> +	OPT_INTEGER(0, "ctl-fd", &stat_config.ctl_fd,
>> +		    "Listen on fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events)"),
>> +	OPT_INTEGER(0, "ctl-fd-ack", &stat_config.ctl_fd_ack,
>> +		    "Send control command completion ('ack') to fd ack descriptor"),
>>  	OPT_END()
>>  };
>>  
>> @@ -2180,6 +2186,8 @@ int cmd_stat(int argc, const char **argv)
>>  	signal(SIGALRM, skip_signal);
>>  	signal(SIGABRT, skip_signal);
>>  
>> +	evlist__initialize_ctlfd(evsel_list, stat_config.ctl_fd, stat_config.ctl_fd_ack);
> 
> please check the return value

Accepted in v4.

~Alexey