Hi Jason, DRM folks,
In DRM-debug currently, drm_debug_enabled() is called a lot to decide whether or not to write debug messages. Each test is cheap, but costs continue with uptime. DYNAMIC_DEBUG "dyndbg", when built with JUMP_LABEL, replaces each of those tests with a patchable NOOP, for "zero cost when off" debugs.
this is v7: - drops RFC distractions -JBaron - drops patch-1: kp->data addition in moduleparams.h not needed -JBaron - rework dyndbg callbacks to use kp->arg instead -JBaron - fixes for problem configs reported -lkp - others noted per patch below ---
Broadly, this patchset does 3 things:
Adds DEFINE_DYNAMIC_DEBUG_CATEGORIES, which defines a mapping from bits to "categorized" pr_debugs, a sysfs interface, and callbacks to implement the bits as dynamic_debug >controls. This is modelled after DRM's debug interface.
Uses the new macro in amdgpu & i915 to control existing pr_debugs according to their ad-hoc categorizations.
Adapts the drm-debug API (~20 macros) to configurably "replace" drm_dbg & drm_dev_dbg with pr_debug & dev_dbg, which avoids drm_debug_enabled() overheads. DEFINE_DYNAMIC_DEBUG_CATEGORIES is used to create the controlling bitmap, which is wired to __drm_debug var so remaining drm_debug_enabled() users stay in sync.
on a virtual box: bash-5.1# for m in i915 amdgpu nouveau; do modprobe $m; done [43833.332326] dyndbg: 384 debug prints in module drm [43833.609577] dyndbg: 211 debug prints in module drm_kms_helper [43833.707124] dyndbg: 2 debug prints in module ttm [43837.471166] dyndbg: 1727 debug prints in module i915 [43838.030774] AMD-Vi: AMD IOMMUv2 driver by Joerg Roedel jroedel@suse.de [43838.031905] AMD-Vi: AMD IOMMUv2 functionality not available on this system [43846.209583] dyndbg: 3852 debug prints in module amdgpu [43846.261391] [drm] amdgpu kernel modesetting enabled. [43846.262512] amdgpu: CRAT table not found [43846.263264] amdgpu: Virtual CRAT table created for CPU [43846.264293] amdgpu: Topology: Add CPU node [43846.743781] dyndbg: 3 debug prints in module wmi [43852.517497] dyndbg: 92 debug prints in module nouveau
There are a few multi-second delays there, just before dyndbg initializes the large blocks of debug prints.
Jim Cromie (8): dyndbg: add DEFINE_DYNAMIC_DEBUG_CATEGORIES and callbacks dyndbg: 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 drm_print: add choice to use dynamic debug in drm-debug drm_print: instrument drm_debug_enabled amdgpu_ucode: reduce number of pr_debug calls nouveau: fold multiple DRM_DEBUG_DRIVERs together
drivers/gpu/drm/Kconfig | 13 + drivers/gpu/drm/Makefile | 3 + 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 | 53 +++- drivers/gpu/drm/i915/Makefile | 4 + drivers/gpu/drm/i915/gvt/debug.h | 18 +- drivers/gpu/drm/i915/i915_params.c | 35 +++ drivers/gpu/drm/nouveau/nouveau_drm.c | 36 ++- include/drm/drm_print.h | 150 +++++++-- include/linux/dynamic_debug.h | 60 ++++ lib/dynamic_debug.c | 79 ++++- 12 files changed, 582 insertions(+), 206 deletions(-)