On Tue, Aug 31, 2021 at 2:21 PM Jim Cromie jim.cromie@gmail.com wrote:
Duplicate drm_debug_enabled() code into both "basic" and "dyndbg" ifdef branches. Then add a pr_debug("todo: ...") into the "dyndbg" branch.
Then convert the "dyndbg" branch's code to a macro, so that its pr_debug() get its callsite info from the invoking function, instead of from drm_debug_enabled() itself.
This gives us unique callsite info for the 8 remaining users of drm_debug_enabled(), and lets us enable them individually to see how much logging traffic they generate. The oft-visited callsites can then be reviewed for runtime cost and possible optimizations.
Heres what we get:
bash-5.1# modprobe drm dyndbg: 384 debug prints in module drm bash-5.1# grep todo: /proc/dynamic_debug/control drivers/gpu/drm/drm_edid.c:1843 [drm]connector_bad_edid =_ "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_print.c:309 [drm]___drm_dbg =p "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_print.c:286 [drm]__drm_dev_dbg =p "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_vblank.c:1491 [drm]drm_vblank_restore =_ "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_vblank.c:787 [drm]drm_crtc_vblank_helper_get_vblank_timestamp_internal =_ "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_vblank.c:410 [drm]drm_crtc_accurate_vblank_count =_ "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_atomic_uapi.c:1457 [drm]drm_mode_atomic_ioctl =_ "todo: maybe avoid via dyndbg\012" drivers/gpu/drm/drm_edid_load.c:178 [drm]edid_load =_ "todo: maybe avoid via dyndbg\012"
At quick glance, edid won't qualify, drm_print might, drm_vblank is strongest chance, maybe atomic-ioctl too.
Signed-off-by: Jim Cromie jim.cromie@gmail.com
heres 120 seconds of enabled todos, from this patch
[jimc@frodo wk-next]$ journalctl -b0 | grep todo | grep 'frodo kernel' [jimc@frodo wk-next]$ sudo su -c 'echo format ^todo: +pfml > /proc/dynamic_debug/control; sleep 120; echo format ^todo: -p > /proc/dynamic_debug/control' [sudo] password for jimc: [jimc@frodo wk-next]$ journalctl -b0 | grep todo | grep 'frodo kernel'
todo-120-log
[jimc@frodo wk-next]$ wc todo-120-log 228 2516 24066 todo-120-log
so overall thats not too much work, not so many bitchecks as to be worth avoiding.
I think I'll try hitting it with my new igt-tools hammer, see what breaks :-)
[jimc@frodo wk-next]$ hsto todo-120-log 120 : drm:drm_crtc_vblank_helper_get_vblank_timestamp_internal:787: todo: maybe avoid via dyndbg 40 : i915:process_csb:1904: todo: maybe avoid via dyndbg 20 : drm:drm_vblank_restore:1491: todo: maybe avoid via dyndbg 20 : drm:drm_crtc_accurate_vblank_count:410: todo: maybe avoid via dyndbg 20 : i915:skl_print_wm_changes:6068: todo: maybe avoid via dyndbg 2 : dyndbg: applied: func="" file="" module="" format="^todo:" lineno=0-0 2 : dyndbg: parsed: func="" file="" module="" format="^todo:" lineno=0-0 1 : dyndbg: split into words: "format" "^todo:" "-p" 1 : dyndbg: split into words: "format" "^todo:" "+pfml" 1 : dyndbg: query 0: "format ^todo: -p" mod:* 1 : dyndbg: query 0: "format ^todo: +pfml" mod:*