From: David Laight <David.Laight@ACULAB.COM>
To: 'Bibo Mao' <maobibo@loongson.cn>, Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
"loongarch@lists.linux.dev" <loongarch@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] LoongArch: add checksum optimization for 64-bit system
Date: Wed, 8 Feb 2023 13:12:47 +0000 [thread overview]
Message-ID: <8fa91bca5e624861b190917933951c7e@AcuMS.aculab.com> (raw)
In-Reply-To: <20230207040148.1801169-1-maobibo@loongson.cn>
From: Bibo Mao
> Sent: 07 February 2023 04:02
>
> loongArch platform is 64-bit system, which supports 8 bytes memory
> accessing, generic checksum function uses 4 byte memory access.
> This patch adds 8-bytes memory access optimization for checksum
> function on loongArch. And the code comes from arm64 system.
>
> When network hw checksum is disabled, iperf performance improves
> about 10% with this patch.
>
...
> +static inline __sum16 csum_fold(__wsum csum)
> +{
> + u32 sum = (__force u32)csum;
> +
> + sum += (sum >> 16) | (sum << 16);
> + return ~(__force __sum16)(sum >> 16);
> +}
Does LoongArch have a rotate instruction?
But for everything except arm (which has a rotate+add instruction)
the best is (probably):
(~sum - rol32(sum, 16)) >> 16
To the point where it is worth killing all the asm
versions and just using that one.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-02-08 13:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-07 4:01 Bibo Mao
2023-02-08 13:12 ` David Laight [this message]
2023-02-08 13:48 ` WANG Xuerui
2023-02-08 14:19 ` David Laight
2023-02-09 1:16 ` maobibo
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