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Date: Fri, 26 Feb 2016 12:29:10 -0800 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Tom Herbert <tom@...bertland.com> Cc: David Miller <davem@...emloft.net>, Network Development <netdev@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Peter Anvin <hpa@...or.com>, "the arch/x86 maintainers" <x86@...nel.org>, kernel-team <kernel-team@...com> Subject: Re: [PATCH v4 net-next] net: Implement fast csum_partial for x86_64 Looks ok to me. I am left wondering if the code should just do that add32_with_carry3(sum, result >> 32, result); in the caller instead - right now pretty much every return point in do_csum() effectively does that, with the exception of - the 0-length case, which is presumably not really an issue in real life and could as well just return 0 - the 8-byte case that does two 32-bit loads instead, but could just do a single 8-byte load and return it (and then the generic version in the caller would do a shift). That would simplifiy the code a bit - it wouldn't need to pass in "sum" to do_csum at all, and we'd have just a single case of that special 3-input carry add.. But I'm certainly ok with it as-is. I'm not sure how performance critical the whole csum routine is, but at least now it doesn't introduce a lot of new complex asm. And this version might be reasonable to make generic, so that non-x86 architectures could use the same approach. That's what we ended up doing for the dcache word-at-a-time code too in the end. Linus
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