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printk: convert the format for KERN_<LEVEL> to a 2 byte pattern

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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>
Cc: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joe Perches 2012-07-30 14:40:17 -07:00 • committed by Linus Torvalds
commit 04d2c8c83d
2 changed files with 16 additions and 13 deletions
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25
include/linux/kern_levels.h
View file

@ -1,22 +1,25 @@
#ifndef __KERN_LEVELS_H__ #ifndef __KERN_LEVELS_H__
#define __KERN_LEVELS_H__ #define __KERN_LEVELS_H__
#define KERN_EMERG "<0>" /* system is unusable */ #define KERN_SOH "\001" /* ASCII Start Of Header */
#define KERN_ALERT "<1>" /* action must be taken immediately */ #define KERN_SOH_ASCII '\001'
#define KERN_CRIT "<2>" /* critical conditions */
#define KERN_ERR "<3>" /* error conditions */ #define KERN_EMERG KERN_SOH "0" /* system is unusable */
#define KERN_WARNING "<4>" /* warning conditions */ #define KERN_ALERT KERN_SOH "1" /* action must be taken immediately */
#define KERN_NOTICE "<5>" /* normal but significant condition */ #define KERN_CRIT KERN_SOH "2" /* critical conditions */
#define KERN_INFO "<6>" /* informational */ #define KERN_ERR KERN_SOH "3" /* error conditions */
#define KERN_DEBUG "<7>" /* debug-level messages */ #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 * 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 * 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). * during early bootup (a continued line is not SMP-safe otherwise).
*/ */
#define KERN_CONT "<c>" #define KERN_CONT KERN_SOH "c"
#endif #endif

4
include/linux/printk.h
View file

@ -9,7 +9,7 @@ extern const char linux_proc_banner[];
static inline int printk_get_level(const char *buffer) 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]) { switch (buffer[1]) {
case '0' ... '7': case '0' ... '7':
case 'd': /* KERN_DEFAULT */ case 'd': /* KERN_DEFAULT */
@ -27,7 +27,7 @@ static inline const char *printk_skip_level(const char *buffer)
case '0' ... '7': case '0' ... '7':
case 'd': /* KERN_DEFAULT */ case 'd': /* KERN_DEFAULT */
case 'c': /* KERN_CONT */ case 'c': /* KERN_CONT */
return buffer + 3; return buffer + 2;
} }
} }
return buffer; return buffer;