Re: [dpdk-dev] [PATCH v3 1/6] eal/arm: add 64-bit armv8 version of rte_memcpy.h

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Fri, Oct 30, 2015 at 01:49:14PM +0000, David Hunt wrote:
> Signed-off-by: David Hunt <david.hunt@intel.com>
> ---
>  .../common/include/arch/arm/rte_memcpy.h           |   4 +
>  .../common/include/arch/arm/rte_memcpy_64.h        | 308 +++++++++++++++++++++
>  2 files changed, 312 insertions(+)
>  create mode 100644 lib/librte_eal/common/include/arch/arm/rte_memcpy_64.h
> 
> diff --git a/lib/librte_eal/common/include/arch/arm/rte_memcpy.h b/lib/librte_eal/common/include/arch/arm/rte_memcpy.h
> index d9f5bf1..1d562c3 100644
> --- a/lib/librte_eal/common/include/arch/arm/rte_memcpy.h
> +++ b/lib/librte_eal/common/include/arch/arm/rte_memcpy.h
> @@ -33,6 +33,10 @@
>  #ifndef _RTE_MEMCPY_ARM_H_
>  #define _RTE_MEMCPY_ARM_H_
>  
> +#ifdef RTE_ARCH_64
> +#include <rte_memcpy_64.h>
> +#else
>  #include <rte_memcpy_32.h>
> +#endif
>  
>  #endif /* _RTE_MEMCPY_ARM_H_ */
> diff --git a/lib/librte_eal/common/include/arch/arm/rte_memcpy_64.h b/lib/librte_eal/common/include/arch/arm/rte_memcpy_64.h
> new file mode 100644
> index 0000000..6d85113
> --- /dev/null
> +++ b/lib/librte_eal/common/include/arch/arm/rte_memcpy_64.h
> @@ -0,0 +1,308 @@
> +/*
> + *   BSD LICENSE
> + *
> + *   Copyright (C) IBM Corporation 2014.
> + *
> + *   Redistribution and use in source and binary forms, with or without
> + *   modification, are permitted provided that the following conditions
> + *   are met:
> + *
> + *     * Redistributions of source code must retain the above copyright
> + *       notice, this list of conditions and the following disclaimer.
> + *     * Redistributions in binary form must reproduce the above copyright
> + *       notice, this list of conditions and the following disclaimer in
> + *       the documentation and/or other materials provided with the
> + *       distribution.
> + *     * Neither the name of IBM Corporation nor the names of its
> + *       contributors may be used to endorse or promote products derived
> + *       from this software without specific prior written permission.
> + *
> + *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
> + *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> + *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
> + *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
> + *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
> + *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
> + *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
> + *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
> + *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
> + *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
> +*/
> +
> +#ifndef _RTE_MEMCPY_ARM_64_H_
> +#define _RTE_MEMCPY_ARM_64_H_
> +
> +#include <stdint.h>
> +#include <string.h>
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +#include "generic/rte_memcpy.h"
> +
> +#ifdef __ARM_NEON_FP

SIMD is not optional in armv8 spec.So every armv8 machine will have
SIMD instruction unlike armv7.More over LDP/STP instruction is
not part of SIMD.So this check is not required or it can
be replaced with a check that select memcpy from either libc or this specific
implementation

> +
> +/* ARM NEON Intrinsics are used to copy data */
> +#include <arm_neon.h>
> +
> +static inline void
> +rte_mov16(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP d0, d1, [%0]\n\t"
> +		     "STP d0, d1, [%1]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}

IMO, no need to hardcode registers used for the mem move(d0, d1).
Let compiler schedule the registers for better performance.


> +
> +static inline void
> +rte_mov32(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP q0, q1, [%0]\n\t"
> +		     "STP q0, q1, [%1]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}
> +
> +static inline void
> +rte_mov48(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP q0, q1, [%0]\n\t"
> +		     "STP q0, q1, [%1]\n\t"
> +		     "LDP d0, d1, [%0 , #32]\n\t"
> +		     "STP d0, d1, [%1 , #32]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}
> +
> +static inline void
> +rte_mov64(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP q0, q1, [%0]\n\t"
> +		     "STP q0, q1, [%1]\n\t"
> +		     "LDP q0, q1, [%0 , #32]\n\t"
> +		     "STP q0, q1, [%1 , #32]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}
> +
> +static inline void
> +rte_mov128(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP q0, q1, [%0]\n\t"
> +		     "STP q0, q1, [%1]\n\t"
> +		     "LDP q0, q1, [%0 , #32]\n\t"
> +		     "STP q0, q1, [%1 , #32]\n\t"
> +		     "LDP q0, q1, [%0 , #64]\n\t"
> +		     "STP q0, q1, [%1 , #64]\n\t"
> +		     "LDP q0, q1, [%0 , #96]\n\t"
> +		     "STP q0, q1, [%1 , #96]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}
> +
> +static inline void
> +rte_mov256(uint8_t *dst, const uint8_t *src)
> +{
> +	asm volatile("LDP q0, q1, [%0]\n\t"
> +		     "STP q0, q1, [%1]\n\t"
> +		     "LDP q0, q1, [%0 , #32]\n\t"
> +		     "STP q0, q1, [%1 , #32]\n\t"
> +		     "LDP q0, q1, [%0 , #64]\n\t"
> +		     "STP q0, q1, [%1 , #64]\n\t"
> +		     "LDP q0, q1, [%0 , #96]\n\t"
> +		     "STP q0, q1, [%1 , #96]\n\t"
> +		     "LDP q0, q1, [%0 , #128]\n\t"
> +		     "STP q0, q1, [%1 , #128]\n\t"
> +		     "LDP q0, q1, [%0 , #160]\n\t"
> +		     "STP q0, q1, [%1 , #160]\n\t"
> +		     "LDP q0, q1, [%0 , #192]\n\t"
> +		     "STP q0, q1, [%1 , #192]\n\t"
> +		     "LDP q0, q1, [%0 , #224]\n\t"
> +		     "STP q0, q1, [%1 , #224]\n\t"
> +		     : : "r" (src), "r" (dst) :
> +	);
> +}
> +
> +#define rte_memcpy(dst, src, n)              \
> +	({ (__builtin_constant_p(n)) ?       \
> +	memcpy((dst), (src), (n)) :          \
> +	rte_memcpy_func((dst), (src), (n)); })
> +
> +static inline void *
> +rte_memcpy_func(void *dst, const void *src, size_t n)
> +{
> +	void *ret = dst;
> +
> +	/* We can't copy < 16 bytes using XMM registers so do it manually. */
> +	if (n < 16) {
> +		if (n & 0x01) {
> +			*(uint8_t *)dst = *(const uint8_t *)src;
> +			dst = (uint8_t *)dst + 1;
> +			src = (const uint8_t *)src + 1;
> +		}
> +		if (n & 0x02) {
> +			*(uint16_t *)dst = *(const uint16_t *)src;
> +			dst = (uint16_t *)dst + 1;
> +			src = (const uint16_t *)src + 1;
> +		}
> +		if (n & 0x04) {
> +			*(uint32_t *)dst = *(const uint32_t *)src;
> +			dst = (uint32_t *)dst + 1;
> +			src = (const uint32_t *)src + 1;
> +		}
> +		if (n & 0x08)
> +			*(uint64_t *)dst = *(const uint64_t *)src;
> +		return ret;
> +	}
> +
> +	/* Special fast cases for <= 128 bytes */
> +	if (n <= 32) {
> +		rte_mov16((uint8_t *)dst, (const uint8_t *)src);
> +		rte_mov16((uint8_t *)dst - 16 + n,
> +			(const uint8_t *)src - 16 + n);
> +		return ret;
> +	}
> +
> +	if (n <= 64) {
> +		rte_mov32((uint8_t *)dst, (const uint8_t *)src);
> +		rte_mov32((uint8_t *)dst - 32 + n,
> +			(const uint8_t *)src - 32 + n);
> +		return ret;
> +	}
> +
> +	if (n <= 128) {
> +		rte_mov64((uint8_t *)dst, (const uint8_t *)src);
> +		rte_mov64((uint8_t *)dst - 64 + n,
> +			(const uint8_t *)src - 64 + n);
> +		return ret;
> +	}
> +
> +	/*
> +	 * For large copies > 128 bytes. This combination of 256, 64 and 16 byte
> +	 * copies was found to be faster than doing 128 and 32 byte copies as
> +	 * well.
> +	 */
> +	for ( ; n >= 256; n -= 256) {

There is room for prefetching the next cacheline based on the cache line
size.

> +		rte_mov256((uint8_t *)dst, (const uint8_t *)src);
> +		dst = (uint8_t *)dst + 256;
> +		src = (const uint8_t *)src + 256;
> +	}
> +
> +	/*
> +	 * We split the remaining bytes (which will be less than 256) into
> +	 * 64byte (2^6) chunks.
> +	 * Using incrementing integers in the case labels of a switch statement
> +	 * enourages the compiler to use a jump table. To get incrementing
> +	 * integers, we shift the 2 relevant bits to the LSB position to first
> +	 * get decrementing integers, and then subtract.
> +	 */
> +	switch (3 - (n >> 6)) {
> +	case 0x00:
> +		rte_mov64((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 64;
> +		dst = (uint8_t *)dst + 64;
> +		src = (const uint8_t *)src + 64;      /* fallthrough */
> +	case 0x01:
> +		rte_mov64((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 64;
> +		dst = (uint8_t *)dst + 64;
> +		src = (const uint8_t *)src + 64;      /* fallthrough */
> +	case 0x02:
> +		rte_mov64((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 64;
> +		dst = (uint8_t *)dst + 64;
> +		src = (const uint8_t *)src + 64;      /* fallthrough */
> +	default:
> +		break;
> +	}
> +
> +	/*
> +	 * We split the remaining bytes (which will be less than 64) into
> +	 * 16byte (2^4) chunks, using the same switch structure as above.
> +	 */
> +	switch (3 - (n >> 4)) {
> +	case 0x00:
> +		rte_mov16((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 16;
> +		dst = (uint8_t *)dst + 16;
> +		src = (const uint8_t *)src + 16;      /* fallthrough */
> +	case 0x01:
> +		rte_mov16((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 16;
> +		dst = (uint8_t *)dst + 16;
> +		src = (const uint8_t *)src + 16;      /* fallthrough */
> +	case 0x02:
> +		rte_mov16((uint8_t *)dst, (const uint8_t *)src);
> +		n -= 16;
> +		dst = (uint8_t *)dst + 16;
> +		src = (const uint8_t *)src + 16;      /* fallthrough */
> +	default:
> +		break;
> +	}
> +
> +	/* Copy any remaining bytes, without going beyond end of buffers */
> +	if (n != 0)
> +		rte_mov16((uint8_t *)dst - 16 + n,
> +			(const uint8_t *)src - 16 + n);
> +	return ret;
> +}
> +
> +#else
> +
> +static inline void
> +rte_mov16(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 16);
> +}
> +
> +static inline void
> +rte_mov32(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 32);
> +}
> +
> +static inline void
> +rte_mov48(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 48);
> +}
> +
> +static inline void
> +rte_mov64(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 64);
> +}
> +
> +static inline void
> +rte_mov128(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 128);
> +}
> +
> +static inline void
> +rte_mov256(uint8_t *dst, const uint8_t *src)
> +{
> +	memcpy(dst, src, 256);
> +}
> +
> +static inline void *
> +rte_memcpy(void *dst, const void *src, size_t n)
> +{
> +	return memcpy(dst, src, n);
> +}
> +
> +static inline void *
> +rte_memcpy_func(void *dst, const void *src, size_t n)
> +{
> +	return memcpy(dst, src, n);
> +}
> +
> +#endif /* __ARM_NEON_FP */
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* _RTE_MEMCPY_ARM_64_H_ */
> -- 
> 1.9.1
>