On Thu, 16 Sep 2010 12:11:41 +0200, Andi Kleen wrote:
On Thu, 16 Sep 2010 17:29:32 +0800
Miao Xie<miaox@xxxxxxxxxxxxxx> wrote:
Ok was a very broken patch. Sorry should have really done some more
work on it. Anyways hopefully the corrected version is good for
testing.
-Andi
title: x86_64/lib: improve the performance of memmove
Implement the 64bit memmmove backwards case using string instructions
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
---
arch/x86/lib/memcpy_64.S | 29 +++++++++++++++++++++++++++++
arch/x86/lib/memmove_64.c | 8 ++++----
2 files changed, 33 insertions(+), 4 deletions(-)
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index bcbcd1e..9de5e9a 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -141,3 +141,32 @@ ENDPROC(__memcpy)
.byte .Lmemcpy_e - .Lmemcpy_c
.byte .Lmemcpy_e - .Lmemcpy_c
.previous
+
+/*
+ * Copy memory backwards (for memmove)
+ * rdi target
+ * rsi source
+ * rdx count
+ */
+
+ENTRY(memcpy_backwards)
+ CFI_STARTPROC
+ std
+ movq %rdi, %rax
+ movl %edx, %ecx
+ addq %rdx, %rdi
+ addq %rdx, %rsi
+ leaq -8(%rdi), %rdi
+ leaq -8(%rsi), %rsi
+ shrl $3, %ecx
+ andl $7, %edx
+ rep movsq
+ addq $7, %rdi
+ addq $7, %rsi
+ movl %edx, %ecx
+ rep movsb
+ cld
+ ret
+ CFI_ENDPROC
+ENDPROC(memcpy_backwards)
+
diff --git a/arch/x86/lib/memmove_64.c b/arch/x86/lib/memmove_64.c
index 0a33909..6774fd8 100644
--- a/arch/x86/lib/memmove_64.c
+++ b/arch/x86/lib/memmove_64.c
@@ -5,16 +5,16 @@
#include <linux/string.h>
#include <linux/module.h>
+extern void * asmlinkage memcpy_backwards(void *dst, const void *src,
+ size_t count);
+
#undef memmove
void *memmove(void *dest, const void *src, size_t count)
{
if (dest < src) {
return memcpy(dest, src, count);
} else {
- char *p = dest + count;
- const char *s = src + count;
- while (count--)
- *--p = *--s;
+ return memcpy_backwards(dest, src, count);
}
return dest;
}
--
1.7.0.1
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