Messages in this thread Patch in this message | | | From | Mark Salyzyn <> | Subject | [PATCH v3] arm64: optimize __memcpy_fromio and __memcpy_toio | Date | Tue, 24 Oct 2017 07:47:14 -0700 |
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__memcpy_fromio and __memcpy_toio functions do not deal well with harmonically unaligned addresses unless they can ultimately be copied as quads (u64) to and from the destination. Without a harmonically aligned relationship, they perform byte operations over the entire buffer.
Dropped the fragment that tried to align on the normal memory, placing a priority on using quad alignment on the io-side.
Removed the volatile on the source for __memcpy_toio as it is unnecessary.
This change was motivated by performance issues in the pstore driver. On a test platform, measuring probe time for pstore, console buffer size of 1/4MB and pmsg of 1/2MB, was in the 90-107ms region. Change managed to reduce it to 10-25ms, an improvement in boot time.
Signed-off-by: Mark Salyzyn <salyzyn@android.com> Cc: Kees Cook <keescook@chromium.org> Cc: Anton Vorontsov <anton@enomsg.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Anton Vorontsov <anton@enomsg.org> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: robin.murphy@arm.com
v2: - simplify, do not try so hard, or through steps, to align on the normal memory side, as it was a diminishing return. Dealing with any pathological short cases was unnecessary since there does not appear to be any. - drop similar __memset_io changes completely.
v3: - do not replace 8 with sizeof(u64)
--- arch/arm64/kernel/io.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/kernel/io.c b/arch/arm64/kernel/io.c index 354be2a872ae..79b17384effa 100644 --- a/arch/arm64/kernel/io.c +++ b/arch/arm64/kernel/io.c @@ -25,8 +25,7 @@ */ void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count) { - while (count && (!IS_ALIGNED((unsigned long)from, 8) || - !IS_ALIGNED((unsigned long)to, 8))) { + while (count && !IS_ALIGNED((unsigned long)from, 8)) { *(u8 *)to = __raw_readb(from); from++; to++; @@ -54,23 +53,22 @@ EXPORT_SYMBOL(__memcpy_fromio); */ void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count) { - while (count && (!IS_ALIGNED((unsigned long)to, 8) || - !IS_ALIGNED((unsigned long)from, 8))) { - __raw_writeb(*(volatile u8 *)from, to); + while (count && !IS_ALIGNED((unsigned long)to, 8)) { + __raw_writeb(*(u8 *)from, to); from++; to++; count--; } while (count >= 8) { - __raw_writeq(*(volatile u64 *)from, to); + __raw_writeq(*(u64 *)from, to); from += 8; to += 8; count -= 8; } while (count) { - __raw_writeb(*(volatile u8 *)from, to); + __raw_writeb(*(u8 *)from, to); from++; to++; count--; -- 2.15.0.rc0.271.g36b669edcc-goog
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