Optimize copy_page by re-arranging instruction sequence and saving register
RFC PATCH v2 2/2 Optimize copy_page by re-arranging instruction sequence and saving register
From: Ma Ling <[email protected]>
Load and write operation occupy about 35% and 10% respectively for most industry benchmarks. Fetched 16-aligned bytes code include about 4 instructions, implying 1.40(0.35 * 4) load, 0.4 write. Modern CPU support 2 load and 1 write per cycle, 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.
---
In this version update comments.
Thanks
Ling
arch/x86/lib/copy_page_64.S | 103 +++++++++++++++++------------------------- 1 files changed, 42 insertions(+), 61 deletions(-)
arch/x86/lib/copy_page_64.S +42 -61
@@ -20,75 +20,56 @@ 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 - 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 +.Loop64: 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 0x8*8(%rsi), %rsi + movq %r10, 0x8*4(%rdi) + movq %rax, 0x8*5(%rdi) + movq %r8, 0x8*6(%rdi) + movq %r9, 0x8*7(%rdi) + leaq 0x8*8(%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 - leaq 64(%rsi), %rsi + 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 0x8*8(%rsi), %rsi + movq %r10, 0x8*4(%rdi) + movq %rax, 0x8*5(%rdi) + movq %r8, 0x8*6(%rdi) + movq %r9, 0x8*7(%rdi) + leaq 0x8*8(%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
Signature · 1 line
1.6.5.2