Date:   Fri, 13 Aug 2021 09:17:08 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     gregkh@...uxfoundation.org, seanpaul@...omium.org,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Jason Baron <jbaron@...mai.com>,
        Hawking Zhang <Hawking.Zhang@....com>,
        Tao Zhou <tao.zhou1@....com>, Huang Rui <ray.huang@....com>,
        Kevin Wang <kevin1.wang@....com>,
        Likun Gao <Likun.Gao@....com>,
        Chengming Gui <Jack.Gui@....com>,
        Aaron Liu <aaron.liu@....com>,
        Jim Cromie <jim.cromie@...il.com>,
        John Clements <john.clements@....com>,
        Ashley Thomas <Ashley.Thomas2@....com>,
        Wyatt Wood <Wyatt.Wood@....com>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
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        Nick Desaulniers <ndesaulniers@...ogle.com>,
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        Andrew Morton <akpm@...ux-foundation.org>,
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        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitor Massaru Iha <vitor@...saru.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Patricia Alfonso <trishalfonso@...gle.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org
Subject: [PATCH v5 0/9] dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and use in DRM

hi Jason, Greg, Daniel, dri-everyone,

drm_debug_enabled() is called a lot (by drm-debug api) to do unlikely
bit-tests to selectively enable debug printing; this is a good job for
DYNAMIC_DEBUG, IFF it is built with JUMP_LABEL.
 
This patchset enables the use of dynamic-debug to avoid those
drm_debug_enabled() overheads, if CONFIG_DRM_USE_DYNAMIC_DEBUG=y.

v5: much rework

- based on Daniel Vetter's feedback, not RFC anymore. (except last one)

- move POC bit_map callback code into dynamic_debug
  add .data to struct kernel_param
  add DEFINE_DYNAMIC_DEBUG_CATEGORIES :
  a declarative interface for bits => control-queries
  this is all new functionality.

- use DEFINE_DYNAMIC_DEBUG_CATEGORIES in i915, amdgpu
  adds selectivity/control to existing categorizations

- DRM_USE_DYNAMIC_DEBUG
  replace DRM_UT_<CAT> (an enum)
  with DRM_CAT_<CAT>   (a prefix string, cpp-prepended to format)
  _UT_ still present, drm_debug_enabled() still used
  todo:
  change __drm_debug param-var to read DDD_CATEGORIES's param-var
  might suffice to keep parallel schemes coherent.
  
- RFC add tracer func as syslog alternate
  test_dynamic_debug.ko: uses tracer for observability, does selftest
  has some misuse risk; calling pr_debug recursively.

v4: (brown-bagger, various fixes after snips)
v3: fixes missed SOB, && on BOL, commit-log tweaks
v2: https://lore.kernel.org/lkml/20210711055003.528167-1-jim.cromie@gmail.com/
v1: https://lore.kernel.org/lkml/20201204035318.332419-1-jim.cromie@gmail.com/

Doing so creates many new pr_debug callsites,
otherwise i915 has ~120 prdbgs, and drm has just 1;

  bash-5.1# modprobe i915
  dyndbg:   8 debug prints in module video
  dyndbg: 305 debug prints in module drm
  dyndbg: 207 debug prints in module drm_kms_helper
  dyndbg:   2 debug prints in module ttm
  dyndbg: 1720 debug prints in module i915

On amdgpu, enabling it adds ~3200 prdbgs, currently at 56 bytes each.
So CONFIG_DRM_USE_DYNAMIC_DEBUG=y affects resource requirements.
Im working on a diet-plan.

Im running this patchset bare-metal on an i7/i915 laptop & an
r9/amdgpu desktop (both as loadable modules).  I booted the amdgpu box
with:

BOOT_IMAGE=(hd2,gpt2)/vmlinuz-5.14.0-rc4-d7a-00009-g5db471cba844 \
     root=UUID=mumble ro \
     rootflags=subvol=root00 rhgb \
     dynamic_debug.verbose=3 main.dyndbg=+p \
     amdgpu.debug=1 amdgpu.test=1 \
     "amdgpu.dyndbg=format ^[ +p"

That last line enables ~1700 prdbg callsites with a format like '[DML'
etc at boot, and amdgpu.test=1 triggers 90 seconds of tests, yielding
~76k prdbgs in 409 seconds, before I turned them off with:

  echo module amdgpu -p > /proc/dynamic_debug/control

Its worth noting, this changes the dyndbg-state underneath settings
applied with `echo > parameters/debug`; the latter is qualitatively
writeonly, maybe a param_get should return "NA" "-1"

this merged cleanly, on top of
commit d65ef4634e5c795a6a4df1d198992c70e9692fb3 (drm-tip/drm-tip)

Jim Cromie (9):
  drm/print: fixup spelling in a comment
  moduleparam: add data member to struct kernel_param
  dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and callbacks
  i915/gvt: remove spaces in pr_debug "gvt: core:" etc prefixes
  i915/gvt: use DEFINE_DYNAMIC_DEBUG_CATEGORIES to create "gvt:core:"
    etc categories
  amdgpu: use DEFINE_DYNAMIC_DEBUG_CATEGORIES to control categorized
    pr_debugs
  drm_print: add choice to use dynamic debug in drm-debug
  amdgpu_ucode: reduce number of pr_debug calls
  dyndbg: RFC add tracer facility RFC

 drivers/gpu/drm/Kconfig                       |  13 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_ucode.c     | 293 ++++++++++--------
 .../gpu/drm/amd/display/dc/core/dc_debug.c    |  44 ++-
 drivers/gpu/drm/drm_print.c                   |  49 ++-
 drivers/gpu/drm/i915/gvt/Makefile             |   4 +
 drivers/gpu/drm/i915/gvt/debug.h              |  18 +-
 drivers/gpu/drm/i915/i915_params.c            |  35 +++
 include/drm/drm_print.h                       | 143 +++++++--
 include/linux/dynamic_debug.h                 |  82 ++++-
 include/linux/moduleparam.h                   |  11 +-
 lib/Kconfig.debug                             |  10 +
 lib/Makefile                                  |   1 +
 lib/dynamic_debug.c                           | 171 ++++++++--
 lib/test_dynamic_debug.c                      | 247 +++++++++++++++
 14 files changed, 901 insertions(+), 220 deletions(-)
 create mode 100644 lib/test_dynamic_debug.c

-- 
2.31.1

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