The patch titled
printk: trivial optimizations
has been added to the -mm tree. Its filename is
printk-trivial-optimizations.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: printk: trivial optimizations
From: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
In arch/x86/boot/printf.c gets rid of unused tail of digits: const char
*digits = "0123456789abcdefghijklmnopqrstuvwxyz"; (we are using 0-9a-f
only)
Uses smaller/faster lowercasing (by ORing with 0x20)
if we know that we work on numbers/digits. Makes
strtoul smaller, and also we are getting rid of
static const char small_digits[] = "0123456789abcdefx";
static const char large_digits[] = "0123456789ABCDEFX";
since this works equally well:
static const char digits[16] = "0123456789ABCDEF";
Size savings:
$ size vmlinux.org vmlinux
text data bss dec hex filename
877320 112252 90112 1079684 107984 vmlinux.org
877048 112252 90112 1079412 107874 vmlinux
It may be also a tiny bit faster because code has less
branches now, but I doubt it is measurable.
Signed-off-by: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/boot/printf.c | 24 +++++++++++--------
lib/vsprintf.c | 48 +++++++++++++++++++++------------------
2 files changed, 40 insertions(+), 32 deletions(-)
diff -puN arch/x86/boot/printf.c~printk-trivial-optimizations arch/x86/boot/printf.c
--- a/arch/x86/boot/printf.c~printk-trivial-optimizations
+++ a/arch/x86/boot/printf.c
@@ -33,8 +33,8 @@ static int skip_atoi(const char **s)
#define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */
-#define SPECIAL 32 /* 0x */
-#define LARGE 64 /* use 'ABCDEF' instead of 'abcdef' */
+#define SMALL 32 /* Must be 32 == 0x20 */
+#define SPECIAL 64 /* 0x */
#define do_div(n,base) ({ \
int __res; \
@@ -45,12 +45,16 @@ __res; })
static char *number(char *str, long num, int base, int size, int precision,
int type)
{
- char c, sign, tmp[66];
- const char *digits = "0123456789abcdefghijklmnopqrstuvwxyz";
+ /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
+ static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
+
+ char tmp[66];
+ char c, sign, locase;
int i;
- if (type & LARGE)
- digits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+ /* locase = 0 or 0x20. ORing digits or letters with 'locase'
+ * produces same digits or (maybe lowercased) letters */
+ locase = (type & SMALL);
if (type & LEFT)
type &= ~ZEROPAD;
if (base < 2 || base > 36)
@@ -81,7 +85,7 @@ static char *number(char *str, long num,
tmp[i++] = '0';
else
while (num != 0)
- tmp[i++] = digits[do_div(num, base)];
+ tmp[i++] = (digits[do_div(num, base)] | locase);
if (i > precision)
precision = i;
size -= precision;
@@ -95,7 +99,7 @@ static char *number(char *str, long num,
*str++ = '0';
else if (base == 16) {
*str++ = '0';
- *str++ = digits[33];
+ *str++ = ('X' | locase);
}
}
if (!(type & LEFT))
@@ -244,9 +248,9 @@ int vsprintf(char *buf, const char *fmt,
base = 8;
break;
- case 'X':
- flags |= LARGE;
case 'x':
+ flags |= SMALL;
+ case 'X':
base = 16;
break;
diff -puN lib/vsprintf.c~printk-trivial-optimizations lib/vsprintf.c
--- a/lib/vsprintf.c~printk-trivial-optimizations
+++ a/lib/vsprintf.c
@@ -26,6 +26,9 @@
#include <asm/page.h> /* for PAGE_SIZE */
#include <asm/div64.h>
+/* Works only for digits and letters, but small and fast */
+#define TOLOWER(x) ((x) | 0x20)
+
/**
* simple_strtoul - convert a string to an unsigned long
* @cp: The start of the string
@@ -41,17 +44,17 @@ unsigned long simple_strtoul(const char
if (*cp == '0') {
base = 8;
cp++;
- if ((toupper(*cp) == 'X') && isxdigit(cp[1])) {
+ if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
cp++;
base = 16;
}
}
} else if (base == 16) {
- if (cp[0] == '0' && toupper(cp[1]) == 'X')
+ if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2;
}
while (isxdigit(*cp) &&
- (value = isdigit(*cp) ? *cp-'0' : toupper(*cp)-'A'+10) < base) {
+ (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
result = result*base + value;
cp++;
}
@@ -92,17 +95,17 @@ unsigned long long simple_strtoull(const
if (*cp == '0') {
base = 8;
cp++;
- if ((toupper(*cp) == 'X') && isxdigit(cp[1])) {
+ if ((TOLOWER(*cp) == 'x') && isxdigit(cp[1])) {
cp++;
base = 16;
}
}
} else if (base == 16) {
- if (cp[0] == '0' && toupper(cp[1]) == 'X')
+ if (cp[0] == '0' && TOLOWER(cp[1]) == 'x')
cp += 2;
}
- while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp)
- ? toupper(*cp) : *cp)-'A'+10) < base) {
+ while (isxdigit(*cp)
+ && (value = isdigit(*cp) ? *cp-'0' : TOLOWER(*cp)-'a'+10) < base) {
result = result*base + value;
cp++;
}
@@ -237,24 +240,25 @@ static noinline char* put_dec(char *buf,
#define PLUS 4 /* show plus */
#define SPACE 8 /* space if plus */
#define LEFT 16 /* left justified */
-#define SPECIAL 32 /* 0x */
-#define LARGE 64 /* use 'ABCDEF' instead of 'abcdef' */
+#define SMALL 32 /* Must be 32 == 0x20 */
+#define SPECIAL 64 /* 0x */
static char *number(char *buf, char *end, unsigned long long num, int base, int size, int precision, int type)
{
- char sign,tmp[66];
- const char *digits;
- /* we are called with base 8, 10 or 16, only, thus don't need "g..." */
- static const char small_digits[] = "0123456789abcdefx"; /* "ghijklmnopqrstuvwxyz"; */
- static const char large_digits[] = "0123456789ABCDEFX"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
+ /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
+ static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
+
+ char tmp[66];
+ char sign;
+ char locase;
int need_pfx = ((type & SPECIAL) && base != 10);
int i;
- digits = (type & LARGE) ? large_digits : small_digits;
+ /* locase = 0 or 0x20. ORing digits or letters with 'locase'
+ * produces same digits or (maybe lowercased) letters */
+ locase = (type & SMALL);
if (type & LEFT)
type &= ~ZEROPAD;
- if (base < 2 || base > 36)
- return NULL;
sign = 0;
if (type & SIGN) {
if ((signed long long) num < 0) {
@@ -281,7 +285,7 @@ static char *number(char *buf, char *end
tmp[i++] = '0';
/* Generic code, for any base:
else do {
- tmp[i++] = digits[do_div(num,base)];
+ tmp[i++] = (digits[do_div(num,base)] | locase);
} while (num != 0);
*/
else if (base != 10) { /* 8 or 16 */
@@ -289,7 +293,7 @@ static char *number(char *buf, char *end
int shift = 3;
if (base == 16) shift = 4;
do {
- tmp[i++] = digits[((unsigned char)num) & mask];
+ tmp[i++] = (digits[((unsigned char)num) & mask] | locase);
num >>= shift;
} while (num);
} else { /* base 10 */
@@ -321,7 +325,7 @@ static char *number(char *buf, char *end
++buf;
if (base == 16) {
if (buf < end)
- *buf = digits[16]; /* for arbitrary base: digits[33]; */
+ *buf = ('X' | locase);
++buf;
}
}
@@ -557,9 +561,9 @@ int vsnprintf(char *buf, size_t size, co
base = 8;
break;
- case 'X':
- flags |= LARGE;
case 'x':
+ flags |= SMALL;
+ case 'X':
base = 16;
break;
_
Patches currently in -mm which might be from vda.linux@xxxxxxxxxxxxxx are
git-cryptodev.patch
maps4-add-proportional-set-size-accounting-in-smaps.patch
printk-trivial-optimizations.patch
-
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