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Date: Thu, 23 Sep 2010 20:01:43 +0800 From: Miao Xie <miaox@...fujitsu.com> To: Ingo Molnar <mingo@...hat.com>, Andi Kleen <andi@...stfloor.org>, Ma Ling <ling.ma@...el.com> CC: Linux Kernel <linux-kernel@...r.kernel.org> Subject: [PATCH -tip] lib,x86_64: improve the performance of memcpy() for unaligned copy memcpy of x86_64 hasn't been optimized for the unaligned copy like other architecture, this patch fixed this problem. I have tested this patch by doing 500 bytes memory copy for 5,000,000 times with various alignments and buffer sizes on my x86_64 box Len Src/Dest Old memcpy New memcpy alignment --- --------- ------------- ------------- 32 0/0 0s 59553us 0s 39597us 32 0/4 0s 37675us 0s 39583us 32 4/0 0s 35720us 0s 39568us 32 4/4 0s 35721us 0s 39564us 256 0/0 0s 88783us 0s 86759us 256 0/4 0s 182896us 0s 166298us 256 4/0 0s 209244us 0s 191853us 256 4/4 0s 262847us 0s 165768us 512 0/0 0s 156486us 0s 148370us 512 0/4 0s 318856us 0s 302365us 512 4/0 0s 412763us 0s 338468us 512 4/4 0s 518688us 0s 218969us 1024 0/0 0s 298076us 0s 268443us 1024 0/4 0s 592114us 0s 575168us 1024 4/0 0s 819969us 0s 654752us 1024 4/4 1s 16405us 0s 343318us Signed-off-by: Miao Xie <miaox@...fujitsu.com> --- arch/x86/lib/memcpy_64.S | 134 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 134 insertions(+), 0 deletions(-) diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S index 75ef61e..32dade1 100644 --- a/arch/x86/lib/memcpy_64.S +++ b/arch/x86/lib/memcpy_64.S @@ -49,6 +49,35 @@ ENTRY(memcpy) jb .Lhandle_tail /* + * the code for unaligned copy is good for large-size copy(>80), + * so if the size is small, we needn't check dst and src is aligned + * or not. + */ + cmp $80, %edx + jbe .Lboth_aligned + + /* + * we found if src is aligned and dest is unaligned, using + * both-aligned copy is better than unaligned copy. So if src is + * aligned, we needn't check dest is aligned or not, just goto + * both-aligned copy. + */ + movq %rsi, %rcx + andq $7, %rcx /* src align check */ + jz .Lboth_aligned + + /* if dest and src both are unaligned, goto unaligned copy */ + movq %rdi, %rcx + andq $7, %rcx /* dst align check */ + jnz .Ldst_unaligned + + /* if src is unaligned and dest is aligned, goto unaligned copy */ + movq %rsi, %rcx + andq $7, %rcx /* src align check */ + jnz .Lsrc_unaligned_dst_aligned + +.Lboth_aligned: + /* * We check whether memory false dependece could occur, * then jump to corresponding copy mode. */ @@ -166,6 +195,111 @@ ENTRY(memcpy) .Lend: retq + + .p2align 4 +.Ldst_unaligned: + negq %rcx + andq $7, %rcx + subq %rcx, %rdx + + /* tune dst address */ + movq (%rsi), %r8 + movq %r8, (%rdi) + addq %rcx, %rdi + addq %rcx, %rsi + + cmp $0x20, %rdx + jb .Lhandle_tail + + movq %rsi, %rcx + andq $7, %rcx /* src align check */ + jz .Lboth_aligned + + .p2align 4 +.Lsrc_unaligned_dst_aligned: + push %rbx + push %r12 + push %r13 + push %r14 + push %r15 + /* + * Calculate how to shift a word read at the memory operation + * aligned srcp to make it aligned for copy. + */ + movq %rsi, %r14 + andq $7, %r14 + shlq $3, %r14 + + movq $64, %r15 + subq %r14, %r15 + + andq $-8, %rsi /* src aligned */ + movq 0*8(%rsi), %r8 + + movq %rdx, %rbx + shrq $5, %rbx + jz .Lsrc_unaligned_less32 + + /* + * %r8 : store src[0] + * %r9 : store src[1] + * %r10: store src[2] + * %r11: store src[3] + * %r12: store src[4] + * %r13: store the tmp data + */ + .p2align 4 +.Lsrc_unaligned_loop32: + movq 1*8(%rsi), %r9 + movq 2*8(%rsi), %r10 + movq 3*8(%rsi), %r11 + movq 4*8(%rsi), %r12 + + movq %r9, %r13 + movb %r14b, %cl + shrq %cl, %r8 + shrq %cl, %r13 + movb %r15b, %cl + shlq %cl, %r9 + orq %r8, %r9 + movq %r10, %r8 + shlq %cl, %r10 + orq %r13, %r10 + + movq %r11, %r13 + movb %r14b, %cl + shrq %cl, %r8 + shrq %cl, %r13 + movb %r15b, %cl + shlq %cl, %r11 + orq %r8, %r11 + movq %r12, %r8 + shlq %cl, %r12 + orq %r13, %r12 + + movq %r9, 0*8(%rdi) + movq %r10, 1*8(%rdi) + movq %r11, 2*8(%rdi) + movq %r12, 3*8(%rdi) + + leaq 4*8(%rdi), %rdi + leaq 4*8(%rsi), %rsi + decq %rbx + jnz .Lsrc_unaligned_loop32 + + .p2align 4 +.Lsrc_unaligned_less32: + shrq $3, %r14 + addq %r14, %rsi + pop %r15 + pop %r14 + pop %r13 + pop %r12 + pop %rbx + andq $31, %rdx + jnz .Lhandle_tail + retq + CFI_ENDPROC ENDPROC(memcpy) ENDPROC(__memcpy) -- 1.7.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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