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