linux-kernel - Re: [RFC 00/21] perf tools: Add user data delayed processing

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Date:   Wed, 24 Jan 2018 13:11:14 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [RFC 00/21] perf tools: Add user data delayed processing

changing wrong subject :-\

On Wed, Jan 24, 2018 at 12:51:22PM +0100, Jiri Olsa wrote:
> hi,
> this RFC contains change to delay sample's user space
> data retrieval into task work, originally described and
> discussed by Peter and Ingo in here [1].
> 
> This patchset tries to follow the original patch with
> some kernel changes (described below) and perf tool
> support included.
> 
> Basically we allow the NMI event code to skip user data
> retrieval and schedule task work to do it, before the
> task resumes.
> 
> Using the task work limits the window where we can do
> this. We can trigger the delayed task work only if the
> taskwork gets executed before the process executes again
> after NMI, because we need its stack as it was in NMI.
> 
> That leaves us with window during the slow syscall path
> (check task_struct::perf_user_data_allowed in patches).
> 
> The slow syscall processing is forced for task when
> the user data event is enabled, which makes the task
> slower.
> 
> On the other hand I noticed roughly 100us drop in NMI
> processing times, which I plotted in here [2].
> 
> Not sure it's worth to introduce this processing, which adds
> more processing time and does not show much improvement. On
> the other hand IIRC Peter mentioned it'd be nice to get user
> space data retrieval out of NMI.
> 
> Also you guys could think of some other better/faster way ;-)
> 
> NOTE I also implemented putting the user stack data into
> delayed processing, which showed nicer numbers. But it's
> little more tricky and brings more changes into this already
> big patchset. The logic stays, so I did not include it to
> keep the patchset simple.
> 
> Also available in:
>   https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
>   perf/user_data
> 
> thanks for comments,
> jirka
> 
> [1] https://marc.info/?l=linux-kernel&m=150098372819938&w=2
> [2] http://people.redhat.com/~jolsa/ud-bench.png
> 
> ---
> Jiri Olsa (21):
>       perf tools: Add perf_evsel__is_sample_bit function
>       perf tools: Add perf_sample__process function
>       perf tools: Add callchain__printf for pure callchain dump
>       perf tools: Add perf_sample__copy|free functions
>       perf: Add TIF_PERF_USER_DATA bit
>       perf: Add PERF_RECORD_USER_DATA event processing
>       perf: Add PERF_SAMPLE_USER_DATA_ID sample type
>       perf: Add PERF_SAMPLE_CALLCHAIN to user data event
>       perf: Export running sample length values through debugfs
>       perf tools: Sync perf_event.h uapi header
>       perf tools: Add perf_sample__parse function
>       perf tools: Add struct parse_args arg to perf_sample__parse
>       perf tools: Add support to parse user data event
>       perf tools: Add support to dump user data event info
>       perf report: Add delayed user data event processing
>       perf record: Enable delayed user data events
>       perf script: Add support to display user data events
>       perf script: Add support to display user data ID
>       perf script: Display USER_DATA misc char for sample
>       perf report: Add user data processing stats
>       perf report: Add --stats=ud option to display user data debug info
> 
>  arch/x86/entry/common.c                  |   6 +++
>  arch/x86/events/core.c                   |  18 ++++++++
>  arch/x86/events/intel/ds.c               |   4 +-
>  arch/x86/include/asm/thread_info.h       |   4 +-
>  include/linux/init_task.h                |   4 +-
>  include/linux/perf_event.h               |   3 ++
>  include/linux/sched.h                    |  20 ++++++++
>  include/uapi/linux/perf_event.h          |  34 +++++++++++++-
>  kernel/events/core.c                     | 283 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  tools/include/uapi/linux/perf_event.h    |  34 +++++++++++++-
>  tools/perf/Documentation/perf-script.txt |   3 +-
>  tools/perf/builtin-record.c              |   2 +
>  tools/perf/builtin-report.c              | 301 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---------
>  tools/perf/builtin-script.c              |  98 +++++++++++++++++++++++++++++++++++++++
>  tools/perf/perf.h                        |   1 +
>  tools/perf/util/event.c                  |   1 +
>  tools/perf/util/event.h                  |   9 ++++
>  tools/perf/util/evsel.c                  | 118 +++++++++++++++++++++++++++++++++++++----------
>  tools/perf/util/evsel.h                  |   5 ++
>  tools/perf/util/session.c                |  60 +++++++++++++++++++-----
>  tools/perf/util/thread.c                 |   1 +
>  tools/perf/util/thread.h                 |  16 +++++++
>  tools/perf/util/tool.h                   |   1 +
>  23 files changed, 954 insertions(+), 72 deletions(-)