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arm64: lib: patch in prfm for copy_page if requested 

On ThunderX T88 pass 1 and pass 2, there is no hardware prefetching so
we need to patch in explicit software prefetching instructions

Prefetching improves this code by 60% over the original code and 2x
over the code without prefetching for the affected hardware using the
benchmark code at https://github.com/apinski-cavium/copy_page_benchmark

Signed-off-by: Andrew Pinski <apinski@cavium.com>
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>
This commit is contained in:
Andrew Pinski 2016-02-02 12:46:26 +00:00 committed by Catalin Marinas
parent 223e23e8aa
commit 60e0a09db2
1 changed files with 17 additions and 0 deletions
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17
arch/arm64/lib/copy_page.S
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@ -18,6 +18,8 @@
#include <linux/const.h>
#include <asm/assembler.h>
#include <asm/page.h>
#include <asm/cpufeature.h>
#include <asm/alternative.h>
/*
* Copy a page from src to dest (both are page aligned)
@ -27,6 +29,15 @@
* x1 - src
*/
ENTRY(copy_page)
alternative_if_not ARM64_HAS_NO_HW_PREFETCH
nop
nop
alternative_else
# Prefetch two cache lines ahead.
prfm pldl1strm, [x1, #128]
prfm pldl1strm, [x1, #256]
alternative_endif
ldp x2, x3, [x1]
ldp x4, x5, [x1, #16]
ldp x6, x7, [x1, #32]
@ -41,6 +52,12 @@ ENTRY(copy_page)
1:
subs x18, x18, #128
alternative_if_not ARM64_HAS_NO_HW_PREFETCH
nop
alternative_else
prfm pldl1strm, [x1, #384]
alternative_endif
stnp x2, x3, [x0]
ldp x2, x3, [x1]
stnp x4, x5, [x0, #16]