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

[Chen Zhou <chenzhou10@huawei.com>]

Hi Will/Robin/Shaokun,

Shaokun's machine broken down, so i tested it.

On KunPeng920 board, the optimised ipv6 header checksum can get
about 1.2 times performance gain and my gcc version is 7.3.0.

Thanks,
Chen Zhou

On 2020/2/3 17:29, Shaokun Zhang wrote:
> 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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