[PATCH 1/2] arm64: mm: only perform memstart_addr sanity check if DEBUG_VM
From: Ard Biesheuvel <hidden>
Date: 2016-02-22 17:46:03
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Checking whether memstart_addr has been assigned every time it is referenced adds a branch instruction that may hurt performance if the reference in question occurs on a hot path. So only perform the check if CONFIG_DEBUG_VM=y. Signed-off-by: Ard Biesheuvel <redacted> --- arch/arm64/include/asm/memory.h | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 68e7d96b9ed3..771d0b506e4b 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h@@ -134,7 +134,11 @@ extern phys_addr_t memstart_addr; /* PHYS_OFFSET - the physical address of the start of memory. */ +#ifndef CONFIG_DEBUG_VM +#define PHYS_OFFSET ({ memstart_addr; }) +#else #define PHYS_OFFSET ({ BUG_ON(memstart_addr & 1); memstart_addr; }) +#endif /* the virtual base of the kernel image (minus TEXT_OFFSET) */ extern u64 kimage_vaddr;
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2.5.0