netdev - Re: [net-next PATCH v3 4/6] udp: Partially unroll handling of first segment and last segment

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Message-ID: <CAF=yD-KTkmx2jzGAeNVLGWmedCEBx8RQWjJBKZzERGCddEnKWw@mail.gmail.com>
Date:   Mon, 7 May 2018 15:54:10 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        David Miller <davem@...emloft.net>
Subject: Re: [net-next PATCH v3 4/6] udp: Partially unroll handling of first
 segment and last segment

On Mon, May 7, 2018 at 2:57 PM, Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
> On Mon, May 7, 2018 at 2:08 PM, Alexander Duyck
> <alexander.duyck@...il.com> wrote:
>> From: Alexander Duyck <alexander.h.duyck@...el.com>
>>
>> This patch allows us to take care of unrolling the first segment and the
>> last segment of the loop for processing the segmented skb. Part of the
>> motivation for this is that it makes it easier to process the fact that the
>> first fame and all of the frames in between should be mostly identical
>> in terms of header data, and the last frame has differences in the length
>> and partial checksum.
>>
>> In addition I am dropping the header length calculation since we don't
>> really need it for anything but the last frame and it can be easily
>> obtained by just pulling the data_len and offset of tail from the transport
>> header.
>>
>> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
>
> I'm not a fan of the more complicated control flow, as I pointed out
> before. It only seems to save one assignment to uh from segs.
>
> Both follow-up patches are now more complex, because they need
> to add the same code in two locations.

With that said, if you feel strongly, I don't object.

The removal of hdrlen and simplification of arguments is definitely
an improvement.