From 223e23e8aa26b0bb62c597637e77295e14f6a62c Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 2 Feb 2016 12:46:25 +0000 Subject: [PATCH] arm64: lib: improve copy_page to deal with 128 bytes at a time We want to avoid lots of different copy_page implementations, settling for something that is "good enough" everywhere and hopefully easy to understand and maintain whilst we're at it. This patch reworks our copy_page implementation based on discussions with Cavium on the list and benchmarking on Cortex-A processors so that: - The loop is unrolled to copy 128 bytes per iteration - The reads are offset so that we read from the next 128-byte block in the same iteration that we store the previous block - Explicit prefetch instructions are removed for now, since they hurt performance on CPUs with hardware prefetching - The loop exit condition is calculated at the start of the loop Signed-off-by: Will Deacon Tested-by: Andrew Pinski Signed-off-by: Catalin Marinas --- arch/arm64/lib/copy_page.S | 46 +++++++++++++++++++++++++++++++------- 1 file changed, 38 insertions(+), 8 deletions(-) diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S index 512b9a7b980e..2534533ceb1d 100644 --- a/arch/arm64/lib/copy_page.S +++ b/arch/arm64/lib/copy_page.S @@ -27,20 +27,50 @@ * x1 - src */ ENTRY(copy_page) - /* Assume cache line size is 64 bytes. */ - prfm pldl1strm, [x1, #64] -1: ldp x2, x3, [x1] + ldp x2, x3, [x1] ldp x4, x5, [x1, #16] ldp x6, x7, [x1, #32] ldp x8, x9, [x1, #48] - add x1, x1, #64 - prfm pldl1strm, [x1, #64] + ldp x10, x11, [x1, #64] + ldp x12, x13, [x1, #80] + ldp x14, x15, [x1, #96] + ldp x16, x17, [x1, #112] + + mov x18, #(PAGE_SIZE - 128) + add x1, x1, #128 +1: + subs x18, x18, #128 + + stnp x2, x3, [x0] + ldp x2, x3, [x1] + stnp x4, x5, [x0, #16] + ldp x4, x5, [x1, #16] + stnp x6, x7, [x0, #32] + ldp x6, x7, [x1, #32] + stnp x8, x9, [x0, #48] + ldp x8, x9, [x1, #48] + stnp x10, x11, [x0, #64] + ldp x10, x11, [x1, #64] + stnp x12, x13, [x0, #80] + ldp x12, x13, [x1, #80] + stnp x14, x15, [x0, #96] + ldp x14, x15, [x1, #96] + stnp x16, x17, [x0, #112] + ldp x16, x17, [x1, #112] + + add x0, x0, #128 + add x1, x1, #128 + + b.gt 1b + stnp x2, x3, [x0] stnp x4, x5, [x0, #16] stnp x6, x7, [x0, #32] stnp x8, x9, [x0, #48] - add x0, x0, #64 - tst x1, #(PAGE_SIZE - 1) - b.ne 1b + stnp x10, x11, [x0, #64] + stnp x12, x13, [x0, #80] + stnp x14, x15, [x0, #96] + stnp x16, x17, [x0, #112] + ret ENDPROC(copy_page)