linux-kernel - [PATCH v6 18/22] dyndbg: reserve flag bit _DPRINTK_FLAGS_PREFIX

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Date:   Mon, 11 Sep 2023 17:08:34 -0600
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org, mcgrof@...nel.org,
        daniel.vetter@...ll.ch
Cc:     linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        amd-gfx@...ts.freedesktop.org, intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, jani.nikula@...el.com,
        ville.syrjala@...ux.intel.com, seanpaul@...omium.org,
        robdclark@...il.com, linux-doc@...r.kernel.org,
        Jim Cromie <jim.cromie@...il.com>
Subject: [PATCH v6 18/22] dyndbg: reserve flag bit _DPRINTK_FLAGS_PREFIX_CACHED

Reserve bit 7 to remember that a pr-debug callsite is/was:
- enabled, with +p
- wants a dynamic-prefix, with one+ of module:function:sourcfile
- was previously called
- was thus saved in the cache. NOT YET.

Its unclear whether any cache fetch would be faster than 2-3 field
fetches, but theres another factor; the 3 columns in the __dyndbg
section are highly redundant and compressible, but to get the
compression, we need field accessors, which will rebalance the
tradeoff.

So, for now, its just the bit reservation.

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 include/linux/dynamic_debug.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index 15edac27cb56..bdb0d12b13ec 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -38,6 +38,7 @@ 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)
 
 #define _DPRINTK_FLAGS_INCL_ANY		\
 	(_DPRINTK_FLAGS_INCL_MODNAME | _DPRINTK_FLAGS_INCL_FUNCNAME |\
-- 
2.41.0