arm64: lib: improve copy_page to deal with 128 bytes at a time

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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 <will.deacon@arm.com>
Tested-by: Andrew Pinski <apinski@cavium.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

...

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Will Deacon 2016-02-02 12:46:25 +00:00 • committed by Catalin Marinas

parent d5370f7548

commit 223e23e8aa

1 changed files with 38 additions and 8 deletions

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arch/arm64/lib/copy_page.S

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