Re: [PATCH] arm64: csum: Optimise IPv6 header checksum

[Shaokun Zhang <zhangshaokun@hisilicon.com>]

Hi Will/Robin,

My apologies for the slow reply because of the Spring Festival in China.

Robin's idea sounds nice, We will test it later because our machine
broke down.

Thanks,
Shaokun

On 2020/1/21 18:34, Will Deacon wrote:
> [+ Shaokun and Lingyan for review and testing feedback]
> 
> On Mon, Jan 20, 2020 at 06:52:29PM +0000, Robin Murphy wrote:
>> Throwing our __uint128_t idioms at csum_ipv6_magic() makes it
>> about 1.3x-2x faster across a range of microarchitecture/compiler
>> combinations. Not much in absolute terms, but every little helps.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@arm.com>
>> ---
>>
>> Before I move on, this seemed like it might be worth touching as well,
>> comparing what other architectures do.
>>
>>  arch/arm64/include/asm/checksum.h |  7 ++++++-
>>  arch/arm64/lib/csum.c             | 27 +++++++++++++++++++++++++++
>>  2 files changed, 33 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/include/asm/checksum.h b/arch/arm64/include/asm/checksum.h
>> index 8d2a7de39744..b6f7bc6da5fb 100644
>> --- a/arch/arm64/include/asm/checksum.h
>> +++ b/arch/arm64/include/asm/checksum.h
>> @@ -5,7 +5,12 @@
>>  #ifndef __ASM_CHECKSUM_H
>>  #define __ASM_CHECKSUM_H
>>  
>> -#include <linux/types.h>
>> +#include <linux/in6.h>
>> +
>> +#define _HAVE_ARCH_IPV6_CSUM
>> +__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
>> +			const struct in6_addr *daddr,
>> +			__u32 len, __u8 proto, __wsum sum);
>>  
>>  static inline __sum16 csum_fold(__wsum csum)
>>  {
>> diff --git a/arch/arm64/lib/csum.c b/arch/arm64/lib/csum.c
>> index 847eb725ce09..4a522e45f23b 100644
>> --- a/arch/arm64/lib/csum.c
>> +++ b/arch/arm64/lib/csum.c
>> @@ -121,3 +121,30 @@ unsigned int do_csum(const unsigned char *buff, int len)
>>  
>>  	return sum >> 16;
>>  }
>> +
>> +__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
>> +			const struct in6_addr *daddr,
>> +			__u32 len, __u8 proto, __wsum csum)
>> +{
>> +	__uint128_t src, dst;
>> +	u64 sum = (__force u64)csum;
>> +
>> +	src = *(const __uint128_t *)saddr->s6_addr;
>> +	dst = *(const __uint128_t *)daddr->s6_addr;
>> +
>> +	sum += (__force u32)htonl(len);
>> +#ifdef __LITTLE_ENDIAN
>> +	sum += (u32)proto << 24;
>> +#else
>> +	sum += proto;
>> +#endif
>> +	src += (src >> 64) | (src << 64);
>> +	dst += (dst >> 64) | (dst << 64);
>> +
>> +	sum = accumulate(sum, src >> 64);
>> +	sum = accumulate(sum, dst >> 64);
>> +
>> +	sum += ((sum >> 32) | (sum << 32));
>> +	return csum_fold((__force __wsum)(sum >> 32));
>> +}
>> +EXPORT_SYMBOL(csum_ipv6_magic);
>> -- 
>> 2.23.0.dirty
>>
> 
> .
> 


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