linux-kernel - [RFC PATCH v2 09/19] dyndbg: optimize ddebug_emit

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Message-Id: <20201225201944.3701590-10-jim.cromie@gmail.com>
Date:   Fri, 25 Dec 2020 13:19:34 -0700
From:   Jim Cromie <jim.cromie@...il.com>
To:     jbaron@...mai.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org
Cc:     Jim Cromie <jim.cromie@...il.com>
Subject: [RFC PATCH v2 09/19] dyndbg: optimize ddebug_emit_prefix

Add early return if no callsite info is specified in site-flags.
This avoids fetching site info that isn't going to be printed.
RFC: is this a proper place to use likely()?

Signed-off-by: Jim Cromie <jim.cromie@...il.com>
---
 include/linux/dynamic_debug.h | 9 +++++++++
 lib/dynamic_debug.c           | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h
index e155dfafc4d9..ea07a91a43bc 100644
--- a/include/linux/dynamic_debug.h
+++ b/include/linux/dynamic_debug.h
@@ -40,6 +40,15 @@ struct _ddebug {
 #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
 #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
 #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
+
+#define _DPRINTK_FLAGS_INCL_ANYSITE		\
+	(_DPRINTK_FLAGS_INCL_MODNAME		\
+	 | _DPRINTK_FLAGS_INCL_FUNCNAME		\
+	 | _DPRINTK_FLAGS_INCL_LINENO)
+#define _DPRINTK_FLAGS_INCL_ANY			\
+	(_DPRINTK_FLAGS_INCL_ANYSITE		\
+	 | _DPRINTK_FLAGS_INCL_TID)
+
 #if defined DEBUG
 #define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
 #else
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index f6d8137e4a46..8e81ce58c1bd 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -629,6 +629,9 @@ static char *dynamic_emit_prefix(const struct _ddebug *dp, char *buf)
 	}
 	pos_after_tid = pos;
 
+	if (!(dp->flags & _DPRINTK_FLAGS_INCL_ANYSITE))
+		return buf;
+
 	if (desc) {
 		if (dp->flags & _DPRINTK_FLAGS_INCL_MODNAME)
 			pos += snprintf(buf + pos, remaining(pos), "%s:",
-- 
2.29.2