drm.debug api provides ~23 macros to issue 10 categories of debug messages, each enabled by a bit in /sys/module/drm/parameters/debug. drm_debug_enabled(category) tests these bits at runtime; while cheap individually, the costs accumulate.
For CONFIG_DRM_USE_DYNAMIC_DEBUG=y, this patchset obsoletes those runtime tests (inside drm_*dbg) by wrapping the 2 fns in one of the dynamic_func_call* Factory macros. The config dependence is due to the .data footprint cost of the tables; AMDGPU has ~4k callsites, at 56 bytes each.
This creates entries in /proc/dynamic_debug/control for each callsite, and each has .class_id = macros'-category. This, and a new query keyword, allow (1st):
# 1=DRM_UT_KMS (iirc) #> echo "module drm class 1 +p > /proc/dynamic_debug/control
Then equivalently: # except it also clears other flags #> echo 0x01 > /sys/module/drm/parameters/debug
dyndbg: - fixes a bug in dyndbg static_key toggling, @stable cc'd - adds support for distinct classes to dyndbg (new,unused feature) - add DECLARE_DYNAMIC_DEBUG_CLASSBITS macro and callbacks to implement bitmap -> classid sysfs knob dyndbg: - drops exported fn: dynamic_debug_exec_queries() any potential users would just use macro, or a tweak on it. - improve info-msg to print both "old -> new" flags drm: - adapts drm to use that support (link category to class_id) - wraps drm_*dbg() in a dyndbg Factory macro to get NOOP optimized debugs this disconnects drm.debug sysfs knob - uses DECLARE_DYNAMIC_DEBUG_CLASSBITS macro this reconnects sysfs knob
This could be -v12, but the focus and subject has wandered a bit, and patchwork CI had multiple different notions of the version. Noteworthy changes:
- no tracefs stuff here, refocus split out already, needs maturation, more attention. its competing with a diet plan, to reduce 56 bytes/callsite. RFC.
Previous drm.debug approach:
- avoided drm_dbg & drm_devdbg by splicing in pr_debug & dev_dbg this preserved the optional decorations: module:function:line:
- used DRM_UT_CORE => "drm:core:" prefix-string, cpp cat'd to formats this made sites selectable by matching to that format prefix
This version:
- .class_id is easier to explain, and no config/format-string diffs
- wraps drm_dbg & drm_devdbg callsites for jumplabel enablement efficiency was original goal.
- loses the optional decorations. drm has its own logmsg standards, doesnt need decorations slapped on later: could recast flags for drm specific decorations
This is based on 5.17-rc4
Its also here: in (dd-drm branch) ghlinux-ro https://github.com/jimc/linux.git (fetch)
I'll push further fixes there as they come.
Jim Cromie (13): dyndbg: fix static_branch manipulation @stable dyndbg: add class_id field and query support dyndbg: add DEFINE_DYNAMIC_DEBUG_CLASSBITS macro and callbacks dyndbg: drop EXPORTed dynamic_debug_exec_queries dyndbg: improve change-info to have old and new dyndbg: abstract dyndbg_site_is_printing drm_print: condense enum drm_debug_category drm_print: interpose drm_*dbg with forwarding macros drm_print: wrap drm_*_dbg in dyndbg jumplabel drm_print: refine drm_debug_enabled for dyndbg+jump-label drm_print: prefer bare printk KERN_DEBUG on generic fn drm_print: add _ddebug desc to drm_*dbg prototypes drm_print: use DEFINE_DYNAMIC_DEBUG_CLASSBITS for drm.debug
.../admin-guide/dynamic-debug-howto.rst | 7 + drivers/gpu/drm/Kconfig | 12 ++ drivers/gpu/drm/Makefile | 2 + drivers/gpu/drm/drm_print.c | 56 ++++--- include/drm/drm_print.h | 80 +++++++--- include/linux/dynamic_debug.h | 113 +++++++++++--- lib/dynamic_debug.c | 140 ++++++++++++++---- 7 files changed, 323 insertions(+), 87 deletions(-)