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Subject: Re: [PATCH v8 00/13] perf: support enable and disable commands in
 stat and record modes
From:   Alexey Budankov <alexey.budankov@linux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>
Cc:     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: <0781a077-aa82-5b4a-273e-c17372a72b93@linux.intel.com>
Organization: Intel Corp.
Message-ID: <4a55f340-0d7a-7dd6-9bd9-7a0d98d63d01@linux.intel.com>
Date:   Mon, 22 Jun 2020 06:38:34 +0300
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Hi,

On 17.06.2020 11:30, Alexey Budankov wrote:
> 
> Changes in v8:
> - avoided moving of fds at fdarray__filter() call
> - skipped counting of fds with zeroed revents at fdarray__filter() call
> - converted explicit --ctl-fd[-ack] into --control fd:ctl-fd[,ack-fd option 
> - updated docs to accommodate --control fd:ctl-fd[,ack-fd] option

Are there any questions or thoughts so far?

Thanks,
Alexey

> 
> v7: https://lore.kernel.org/lkml/5de4b954-24f0-1e8d-5a0d-7b12783b8218@linux.intel.com/
> 
> Changes in v7:
> - added missing perf-record.txt changes 
> - adjusted docs wording for --ctl-fd,ctl-fd-ack options 
>   to additionally mention --delay=-1 effect
> 
> v6: https://lore.kernel.org/lkml/f8e3a714-d9b1-4647-e1d2-9981cbaa83ec@linux.intel.com/
> 
> Changes in v6:
> - split re-factoring of events handling loops for stat mode
>   into smaller incremental parts
> - added parts missing at v5
> - corrected v5 runtime issues
> 
> v5: https://lore.kernel.org/lkml/e5cac8dd-7aa4-ec7c-671c-07756907acba@linux.intel.com/
> 
> Changes in v5:
> - split re-factoring of events handling loops for stat mode
>   into smaller incremental parts
> 
> v4: https://lore.kernel.org/lkml/653fe5f3-c986-a841-1ed8-0a7d2fa24c00@linux.intel.com/
> 
> Changes in v4:
> - made checking of ctlfd state unconditional in record trace streaming loop
> - introduced static poll fds to keep evlist__filter_pollfd() unaffected
> - handled ret code of evlist__initialize_ctlfd() where need
> - renamed and structured handle_events() function
> - applied anonymous structs where needed
> 
> v3: https://lore.kernel.org/lkml/eb38e9e5-754f-d410-1d9b-e26b702d51b7@linux.intel.com/
> 
> Changes in v3:
> - renamed functions and types from perf_evlist_ to evlist_ to avoid
>   clash with libperf code;
> - extended commands to be strings of variable length consisting of
>   command name and also possibly including command specific data;
> - merged docs update with the code changes;
> - updated docs for -D,--delay=-1 option for stat and record modes;
> 
> v2: https://lore.kernel.org/lkml/d582cc3d-2302-c7e2-70d3-bc7ab6f628c3@linux.intel.com/
> 
> Changes in v2:
> - renamed resume and pause commands to enable and disable ones, renamed
>   CTL_CMD_RESUME and CTL_CMD_PAUSE to CTL_CMD_ENABLE and CTL_CMD_DISABLE
>   to fit to the appropriate ioctls and avoid mixing up with PAUSE_OUTPUT
>   ioctl;
> - factored out event handling loop into a handle_events() for stat mode;
> - separated -D,--delay=-1 into separate patches for stat and record modes;
> 
> v1: https://lore.kernel.org/lkml/825a5132-b58d-c0b6-b050-5a6040386ec7@linux.intel.com/
> 
> repo: tip of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git perf/core
> 
> The patch set implements handling of 'start disabled', 'enable' and 'disable'
> external control commands which can be provided for stat and record modes
> of the tool from an external controlling process. 'start disabled' command
> can be used to postpone enabling of events in the beginning of a monitoring
> session. 'enable' and 'disable' commands can be used to enable and disable
> events correspondingly any time after the start of the session.
> 
> The 'start disabled', 'enable' and 'disable' external control commands can be
> used to focus measurement on specially selected time intervals of workload
> execution. Focused measurement reduces tool intrusion and influence on
> workload behavior, reduces distortion and amount of collected and stored
> data, mitigates data accuracy loss because measurement and data capturing
> happen only during intervals of interest.
> 
> A controlling process can be a bash shell script [1], native executable or
> any other language program that can directly work with file descriptors,
> e.g. pipes [2], and spawn a process, specially the tool one.
> 
> -D,--delay <val> option is extended with -1 value to skip events enabling
> in the beginning of a monitoring session ('start disabled' command).
> --control fd:ctl-fd[,ack-fd] command line option is introduced to provide the
> tool with a pair of file descriptors to listen to control commands and reply
> to the controlling process on the completion of received commands.
> 
> The tool reads control command message from ctl-fd descriptor, handles the
> command and optionally replies acknowledgement message to ack-fd descriptor,
> if it is specified on the command line. 'enable' command is recognized as
> 'enable' string message and 'disable' command is recognized as 'disable'
> string message both received from ctl-fd descriptor. Completion message is
> 'ack\n' and sent to ack-fd descriptor.
> 
> Example bash script demonstrating simple use case follows:
> 
> #!/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       \
>           --control fd:${ctl_fd},${ctl_fd_ack} \
>           -- sleep 40 &
> 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})"
> sleep 5  && echo 'enable' >&${ctl_fd} && read -u ${ctl_fd_ack} e2 && echo "enabled(${e2})"
> sleep 10 && echo 'disable' >&${ctl_fd} && read -u ${ctl_fd_ack} d2 && echo "disabled(${d2})"
> 
> exec {ctl_fd_ack}>&- && unlink ${ctl_ack_fifo}
> exec {ctl_fd}>&- && unlink ${ctl_fifo}
> 
> wait -n ${perf_pid}
> exit $?
> 
> 
> Script output:
> 
> [root@host dir] example
> Events disabled
> #           time             counts unit events
>      1.001101062      <not counted>      cpu-cycles                                                  
>      2.002994944      <not counted>      cpu-cycles                                                  
>      3.004864340      <not counted>      cpu-cycles                                                  
>      4.006727177      <not counted>      cpu-cycles                                                  
> Events enabled
> enabled(ack)
>      4.993808464          3,124,246      cpu-cycles                                                  
>      5.008597004          3,325,624      cpu-cycles                                                  
>      6.010387483         83,472,992      cpu-cycles                                                  
>      7.012266598         55,877,621      cpu-cycles                                                  
>      8.014175695         97,892,729      cpu-cycles                                                  
>      9.016056093         68,461,242      cpu-cycles                                                  
>     10.017937507         55,449,643      cpu-cycles                                                  
>     11.019830154         68,938,167      cpu-cycles                                                  
>     12.021719952         55,164,101      cpu-cycles                                                  
>     13.023627550         70,535,720      cpu-cycles                                                  
>     14.025580995         53,240,125      cpu-cycles                                                  
> disabled(ack)
>     14.997518260         53,558,068      cpu-cycles                                                  
> Events disabled
>     15.027216416      <not counted>      cpu-cycles                                                  
>     16.029052729      <not counted>      cpu-cycles                                                  
>     17.030904762      <not counted>      cpu-cycles                                                  
>     18.032073424      <not counted>      cpu-cycles                                                  
>     19.033805074      <not counted>      cpu-cycles                                                  
> Events enabled
> enabled(ack)
>     20.001279097          3,021,022      cpu-cycles                                                  
>     20.035044381          6,434,367      cpu-cycles                                                  
>     21.036923813         89,358,251      cpu-cycles                                                  
>     22.038825169         72,516,351      cpu-cycles                                                  
> #           time             counts unit events
>     23.040715596         55,046,157      cpu-cycles                                                  
>     24.042643757         78,128,649      cpu-cycles                                                  
>     25.044558535         61,052,428      cpu-cycles                                                  
>     26.046452785         62,142,806      cpu-cycles                                                  
>     27.048353021         74,477,971      cpu-cycles                                                  
>     28.050241286         61,001,623      cpu-cycles                                                  
>     29.052149961         61,653,502      cpu-cycles                                                  
> disabled(ack)
>     30.004980264         82,729,640      cpu-cycles                                                  
> Events disabled
>     30.053516176      <not counted>      cpu-cycles                                                  
>     31.055348366      <not counted>      cpu-cycles                                                  
>     32.057202097      <not counted>      cpu-cycles                                                  
>     33.059040702      <not counted>      cpu-cycles                                                  
>     34.060843288      <not counted>      cpu-cycles                                                  
>     35.000888624      <not counted>      cpu-cycles                                                  
> [root@host dir]# 
> 
> [1] http://man7.org/linux/man-pages/man1/bash.1.html
> [2] http://man7.org/linux/man-pages/man2/pipe.2.html
> 
> ---
> Alexey Budankov (13):
>   tools/libperf: avoid moving of fds at fdarray__filter() call
>   perf evlist: introduce control file descriptors
>   perf evlist: implement control command handling functions
>   perf stat: factor out body of event handling loop for system wide
>   perf stat: move target check to loop control statement
>   perf stat: factor out body of event handling loop for fork case
>   perf stat: factor out event handling loop into dispatch_events()
>   perf stat: extend -D,--delay option with -1 value
>   perf stat: implement control commands handling
>   perf stat: introduce --control fd:ctl-fd[,ack-fd] options
>   perf record: extend -D,--delay option with -1 value
>   perf record: implement control commands handling
>   perf record: introduce --control fd:ctl-fd[,ack-fd] options
> 
>  tools/lib/api/fd/array.c                 |  11 +-
>  tools/perf/Documentation/perf-record.txt |  44 +++++-
>  tools/perf/Documentation/perf-stat.txt   |  44 +++++-
>  tools/perf/builtin-record.c              |  65 ++++++++-
>  tools/perf/builtin-stat.c                | 176 ++++++++++++++++++-----
>  tools/perf/builtin-trace.c               |   2 +-
>  tools/perf/tests/fdarray.c               |  20 +--
>  tools/perf/util/evlist.c                 | 136 ++++++++++++++++++
>  tools/perf/util/evlist.h                 |  25 ++++
>  tools/perf/util/record.h                 |   4 +-
>  tools/perf/util/stat.h                   |   4 +-
>  11 files changed, 458 insertions(+), 73 deletions(-)
>