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Date: Thu, 11 Oct 2012 20:29:08 +0800 From: ling.ma@...el.com To: mingo@...e.hu Cc: hpa@...or.com, tglx@...utronix.de, linux-kernel@...r.kernel.org, Ma Ling <ling.ma@...el.com> Subject: [PATCH RFC 2/2] [x86] Optimize copy_page by re-arranging instruction sequence and saving register From: Ma Ling <ling.ma@...el.com> Load and write operation occupy about 35% and 10% respectively for most industry benchmarks. Fetched 16-aligned bytes code include about 4 instructions, implying 1.34(0.35 * 4) load, 0.4 write. Modern CPU support 2 load and 1 write per cycle, so throughput from write is bottleneck for memcpy or copy_page, and some slight CPU only support one mem operation per cycle. So it is enough to issue one read and write instruction per cycle, and we can save registers. In this patch we also re-arrange instruction sequence to improve performance The performance on atom is improved about 11%, 9% on hot/cold-cache case respectively. Signed-off-by: Ma Ling <ling.ma@...el.com> --- arch/x86/lib/copy_page_64.S | 103 +++++++++++++++++------------------------- 1 files changed, 42 insertions(+), 61 deletions(-) diff --git a/arch/x86/lib/copy_page_64.S b/arch/x86/lib/copy_page_64.S index 3da5527..13c97f4 100644 --- a/arch/x86/lib/copy_page_64.S +++ b/arch/x86/lib/copy_page_64.S @@ -20,76 +20,57 @@ ENDPROC(copy_page_rep) ENTRY(copy_page) CFI_STARTPROC - subq $2*8, %rsp - CFI_ADJUST_CFA_OFFSET 2*8 - movq %rbx, (%rsp) - CFI_REL_OFFSET rbx, 0 - movq %r12, 1*8(%rsp) - CFI_REL_OFFSET r12, 1*8 + mov $(4096/64)-5, %ecx - movl $(4096/64)-5, %ecx - .p2align 4 .Loop64: - dec %rcx - - movq 0x8*0(%rsi), %rax - movq 0x8*1(%rsi), %rbx - movq 0x8*2(%rsi), %rdx - movq 0x8*3(%rsi), %r8 - movq 0x8*4(%rsi), %r9 - movq 0x8*5(%rsi), %r10 - movq 0x8*6(%rsi), %r11 - movq 0x8*7(%rsi), %r12 - prefetcht0 5*64(%rsi) - - movq %rax, 0x8*0(%rdi) - movq %rbx, 0x8*1(%rdi) - movq %rdx, 0x8*2(%rdi) - movq %r8, 0x8*3(%rdi) - movq %r9, 0x8*4(%rdi) - movq %r10, 0x8*5(%rdi) - movq %r11, 0x8*6(%rdi) - movq %r12, 0x8*7(%rdi) - - leaq 64 (%rsi), %rsi - leaq 64 (%rdi), %rdi - + decb %cl + + movq 0x8*0(%rsi), %r10 + movq 0x8*1(%rsi), %rax + movq 0x8*2(%rsi), %r8 + movq 0x8*3(%rsi), %r9 + movq %r10, 0x8*0(%rdi) + movq %rax, 0x8*1(%rdi) + movq %r8, 0x8*2(%rdi) + movq %r9, 0x8*3(%rdi) + + movq 0x8*4(%rsi), %r10 + movq 0x8*5(%rsi), %rax + movq 0x8*6(%rsi), %r8 + movq 0x8*7(%rsi), %r9 + leaq 64(%rsi), %rsi + movq %r10, 0x8*4(%rdi) + movq %rax, 0x8*5(%rdi) + movq %r8, 0x8*6(%rdi) + movq %r9, 0x8*7(%rdi) + leaq 64(%rdi), %rdi jnz .Loop64 - movl $5, %ecx - .p2align 4 + mov $5, %dl .Loop2: - decl %ecx - - movq 0x8*0(%rsi), %rax - movq 0x8*1(%rsi), %rbx - movq 0x8*2(%rsi), %rdx - movq 0x8*3(%rsi), %r8 - movq 0x8*4(%rsi), %r9 - movq 0x8*5(%rsi), %r10 - movq 0x8*6(%rsi), %r11 - movq 0x8*7(%rsi), %r12 - - movq %rax, 0x8*0(%rdi) - movq %rbx, 0x8*1(%rdi) - movq %rdx, 0x8*2(%rdi) - movq %r8, 0x8*3(%rdi) - movq %r9, 0x8*4(%rdi) - movq %r10, 0x8*5(%rdi) - movq %r11, 0x8*6(%rdi) - movq %r12, 0x8*7(%rdi) - - leaq 64(%rdi), %rdi + decb %dl + movq 0x8*0(%rsi), %r10 + movq 0x8*1(%rsi), %rax + movq 0x8*2(%rsi), %r8 + movq 0x8*3(%rsi), %r9 + movq %r10, 0x8*0(%rdi) + movq %rax, 0x8*1(%rdi) + movq %r8, 0x8*2(%rdi) + movq %r9, 0x8*3(%rdi) + + movq 0x8*4(%rsi), %r10 + movq 0x8*5(%rsi), %rax + movq 0x8*6(%rsi), %r8 + movq 0x8*7(%rsi), %r9 leaq 64(%rsi), %rsi + movq %r10, 0x8*4(%rdi) + movq %rax, 0x8*5(%rdi) + movq %r8, 0x8*6(%rdi) + movq %r9, 0x8*7(%rdi) + leaq 64(%rdi), %rdi jnz .Loop2 - movq (%rsp), %rbx - CFI_RESTORE rbx - movq 1*8(%rsp), %r12 - CFI_RESTORE r12 - addq $2*8, %rsp - CFI_ADJUST_CFA_OFFSET -2*8 ret .Lcopy_page_end: CFI_ENDPROC -- 1.6.5.2 -- 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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