[PATCH 7/8] printk: Convert the format for KERN_ to a 2 byte pattern

Joe Perches
2012-06-05T09:48:03Z

Instead of "<.>", use an ASCII SOH for the KERN_<LEVEL>
prefix initiator.

This saves 1 byte per printk, thousands of bytes in a normal kernel.

No output changes are produced as vprintk_emit converts these
uses to "<.>".

Signed-off-by: Joe Perches <joe@perches.com>
---
include/linux/kern_levels.h | 25 ++++++++++++++-----------
include/linux/printk.h | 4 ++--
kernel/printk.c | 3 ++-
3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h
index 337e56f..8c719a9 100644
--- a/include/linux/kern_levels.h
+++ b/include/linux/kern_levels.h
@@ -1,22 +1,25 @@
#ifndef __KERN_LEVELS_H__
#define __KERN_LEVELS_H__

-#define KERN_EMERG "<0>" /* system is unusable */
-#define KERN_ALERT "<1>" /* action must be taken immediately */
-#define KERN_CRIT "<2>" /* critical conditions */
-#define KERN_ERR "<3>" /* error conditions */
-#define KERN_WARNING "<4>" /* warning conditions */
-#define KERN_NOTICE "<5>" /* normal but significant condition */
-#define KERN_INFO "<6>" /* informational */
-#define KERN_DEBUG "<7>" /* debug-level messages */
+#define KERN_SOH "\001" /* ASCII Start Of Header */
+#define KERN_SOH_ASCII '\001'
+
+#define KERN_EMERG KERN_SOH "0" /* system is unusable */
+#define KERN_ALERT KERN_SOH "1" /* action must be taken immediately */
+#define KERN_CRIT KERN_SOH "2" /* critical conditions */
+#define KERN_ERR KERN_SOH "3" /* error conditions */
+#define KERN_WARNING KERN_SOH "4" /* warning conditions */
+#define KERN_NOTICE KERN_SOH "5" /* normal but significant condition */
+#define KERN_INFO KERN_SOH "6" /* informational */
+#define KERN_DEBUG KERN_SOH "7" /* debug-level messages */
+
+#define KERN_DEFAULT KERN_SOH "d" /* the default kernel loglevel */

-/* Use the default kernel loglevel */
-#define KERN_DEFAULT "<d>"
/*
* Annotation for a "continued" line of log printout (only done after a
* line that had no enclosing \n). Only to be used by core/arch code
* during early bootup (a continued line is not SMP-safe otherwise).
*/
-#define KERN_CONT "<c>"
+#define KERN_CONT KERN_SOH "c"

#endif
diff --git a/include/linux/printk.h b/include/linux/printk.h
index fea2de3..93a231f 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -9,7 +9,7 @@ extern const char linux_proc_banner[];

static inline int printk_get_level(const char *buffer)
{
- if (buffer[0] == '<' && buffer[1] && buffer[2] == '>') {
+ if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
switch (buffer[1]) {
case '0' ... '7':
case 'd': /* KERN_DEFAULT */
@@ -27,7 +27,7 @@ static inline const char *printk_skip_level(const char *buffer)
case '0' ... '7':
case 'd': /* KERN_DEFAULT */
case 'c': /* KERN_CONT */
- return buffer + 3;
+ return buffer + 2;
}
}
return buffer;
diff --git a/kernel/printk.c b/kernel/printk.c
index 7cce9c5..5cd73f7 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -1340,9 +1340,10 @@ asmlinkage int vprintk_emit(int facility, int level,
case 'd': /* KERN_DEFAULT */
prefix = true;
case 'c': /* KERN_CONT */
+ break;
}
text_len -= end_of_header - text;
- text = end_of_header;
+ text = (char *)end_of_header;
}

if (level == -1)
--
1.7.8.111.gad25c.dirty