Le 20/03/2025 à 19:51, Jim Cromie a écrit :
Add _INCL_LOOKUP condition to separate +mfsl flags from +t, allowing
(after refactoring) to avoid a needless call-return.
Add a PREFIX_CACHED bit to remember that a pr-debug callsite is:
- enabled, with +p
- wants a dynamic-prefix, with _INCL_LOOKUP
- was previously called
- was thus saved in the prefix cache. NOT YET.
>
This allows (later) to cache part/all of the dynamic-prefix for each
pr_debug that gets called.
NOTES:
dyndbg's dynamic prefixing can get expensive; each enabled callsite's
prefix is sprintf'd into stack-mem, every time a pr_debug is called.
A cache would help, if callsites mark _DPRINTK_FLAGS_PREFIX_CACHED
after saving the prefix string. But not yet.
-t thread-id. not part of the "callsite" info, derived from current.
doesn't belong in the cache. it would be wrong.
can be done in outer: dynamic_emit_prefix()
-mfsl module, function, source-file, line
we cache these, composed into a sub-string.
they are "lookups", currently to descriptor fields,.
could be accessor macros to "compressed" tables.
All enabled together, they compose a prefix string like:
# outer -----inner-------------------
"[tid] module:function:sourcfile:line: "
s/sourcfile/sourcesfile/
So this patch extracts _DPRINTK_FLAGS_INCL_LOOKUP macro out of
_DPRINTK_FLAGS_INCL_ANY macro, then redefs latter.
Next re-refactor dynamic_emit_prefix inner/outer fns accordingly.
This commit introduces two things:
- introduction of _DPRINTK_FLAGS_INCL_LOOKUP, used in a future patch
- introduction of _DPRINTK_FLAGS_PREFIX_CACHED, not used in this series
I don't think those changes are needed to fix DYNDBG_CLASSMAP, it seems
to be an (unfinished?) optimization, so it could make sense to move it
to an independent series. Please tell me if I overlooked something!
Signed-off-by: Jim Cromie <jim.cro...@gmail.com>
---
include/linux/dynamic_debug.h | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index c388ab05a6e1..82eabaa6e827 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -38,11 +38,13 @@ struct _ddebug {
#define _DPRINTK_FLAGS_INCL_LINENO (1<<3)
#define _DPRINTK_FLAGS_INCL_TID (1<<4)
#define _DPRINTK_FLAGS_INCL_SOURCENAME (1<<5)
+#define _DPRINTK_FLAGS_PREFIX_CACHED (1<<7)
Is there a reason to skip 1 << 6? I don't see any usage of this flag in
this series, maybe you can skip it for now and introduce it with the
actual implementation of the cache system?
Also, I think it make sense to add some documentation on this define.
All the other are controlled by the user, but PREFIX_CACHED is
controlled by the "dyndbg core", so maybe add something like:
/**
* _DPRINTK_FLAGS_PREFIX_CACHED - Mark a printk prefix as cached
* This bit is set by the callsite to avoid regenerating fixed
* part of the prefix at each call
*/
-#define _DPRINTK_FLAGS_INCL_ANY \
- (_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
- _DPRINTK_FLAGS_INCL_LINENO | _DPRINTK_FLAGS_INCL_TID |\
- _DPRINTK_FLAGS_INCL_SOURCENAME)
+#define _DPRINTK_FLAGS_INCL_LOOKUP \
+ (_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME | \
+ _DPRINTK_FLAGS_INCL_SOURCENAME | _DPRINTK_FLAGS_INCL_LINENO)
+#define _DPRINTK_FLAGS_INCL_ANY
\
+ (_DPRINTK_FLAGS_INCL_TID | _DPRINTK_FLAGS_INCL_LOOKUP)
#if defined DEBUG
#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
--
Louis Chauvet, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
