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authorRobin Getz <robin.getz@analog.com>2010-05-04 14:59:21 +0000
committerMike Frysinger <vapier@gentoo.org>2010-05-22 14:19:11 -0400
commit648eee52ccdc623e21b920d6048e93490a4860a7 (patch)
tree1d106f156abb6c7a0169a392f4856cd63893e079 /arch/blackfin/lib
parentc70dcabc8eba18113a4735e7b1bd09f7493e38f0 (diff)
downloadlinux-linaro-stable-648eee52ccdc623e21b920d6048e93490a4860a7.tar.gz
Blackfin: optimize strncpy a bit
Add a little strncpy optimization which can easily cut boot time by 20%. When the kernel is booting with initramfs, it builds up the filesystem from a cpio archive by calling strncpy_from_user() via fs/namei.c's do_getname() on every file in the archive (which can be lots) with a length of PATH_MAX (1024). This causes the dest of the strncpy to be padded with many NUL bytes. This optimization mostly causes these NUL bytes to be padded with a call to memset() which is already optimized for filling memory quickly, but the hardware loop helps a little bit as well. Boot time measured with 'loglevel=0' so UART speed doesn't get in the way. Signed-off-by: Robin Getz <robin.getz@analog.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Diffstat (limited to 'arch/blackfin/lib')
-rw-r--r--arch/blackfin/lib/memset.S1
-rw-r--r--arch/blackfin/lib/strncpy.S59
2 files changed, 47 insertions, 13 deletions
diff --git a/arch/blackfin/lib/memset.S b/arch/blackfin/lib/memset.S
index c30d99b10969..eab1bef3f5bf 100644
--- a/arch/blackfin/lib/memset.S
+++ b/arch/blackfin/lib/memset.S
@@ -20,6 +20,7 @@
* R1 = filler byte
* R2 = count
* Favours word aligned data.
+ * The strncpy assumes that I0 and I1 are not used in this function
*/
ENTRY(_memset)
diff --git a/arch/blackfin/lib/strncpy.S b/arch/blackfin/lib/strncpy.S
index 39fbbe6523e5..f3931d50b4a7 100644
--- a/arch/blackfin/lib/strncpy.S
+++ b/arch/blackfin/lib/strncpy.S
@@ -5,12 +5,14 @@
*/
#include <linux/linkage.h>
+#include <asm/context.S>
/* void *strncpy(char *dest, const char *src, size_t n);
* R0 = address (dest)
* R1 = address (src)
* R2 = size
- * Returns a pointer to the destination string dest
+ * Returns a pointer (R0) to the destination string dest
+ * we do this by not changing R0
*/
#ifdef CONFIG_STRNCPY_L1
@@ -24,29 +26,60 @@
ENTRY(_strncpy)
CC = R2 == 0;
if CC JUMP 4f;
+
+ P2 = R2 ; /* size */
P0 = R0 ; /* dst*/
P1 = R1 ; /* src*/
+ LSETUP (1f, 2f) LC0 = P2;
1:
R1 = B [P1++] (Z);
B [P0++] = R1;
- CC = R1;
- if ! cc jump 2f;
- R2 += -1;
- CC = R2 == 0;
- if ! cc jump 1b (bp);
- jump 4f;
+ CC = R1 == 0;
2:
- /* if src is shorter than n, we need to null pad bytes in dest */
- R1 = 0;
+ if CC jump 3f;
+
+ RTS;
+
+ /* if src is shorter than n, we need to null pad bytes in dest
+ * but, we can get here when the last byte is zero, and we don't
+ * want to copy an extra byte at the end, so we need to check
+ */
3:
+ R2 = LC0;
+ CC = R2
+ if ! CC jump 6f;
+
+ /* if the required null padded portion is small, do it here, rather than
+ * handling the overhead of memset (which is OK when things are big).
+ */
+ R3 = 0x20;
+ CC = R2 < R3;
+ IF CC jump 4f;
+
R2 += -1;
- CC = R2 == 0;
- if cc jump 4f;
- B [P0++] = R1;
- jump 3b;
+
+ /* Set things up for memset
+ * R0 = address
+ * R1 = filler byte (this case it's zero, set above)
+ * R2 = count (set above)
+ */
+
+ I1 = R0;
+ R0 = RETS;
+ I0 = R0;
+ R0 = P0;
+ pseudo_long_call _memset, p0;
+ R0 = I0;
+ RETS = R0;
+ R0 = I1;
+ RTS;
4:
+ LSETUP(5f, 5f) LC0;
+5:
+ B [P0++] = R1;
+6:
RTS;
ENDPROC(_strncpy)