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>
diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S
index 2534533..4c1e700 100644
--- a/arch/arm64/lib/copy_page.S
+++ b/arch/arm64/lib/copy_page.S
@@ -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 @@
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]