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

On Mon, May 7, 2018 at 3:59 PM, Alexander Duyck
[off-list ref] wrote:

On Mon, May 7, 2018 at 12:54 PM, Willem de Bruijn
[off-list ref] wrote:

quoted

On Mon, May 7, 2018 at 2:57 PM, Willem de Bruijn
[off-list ref] wrote:

quoted

On Mon, May 7, 2018 at 2:08 PM, Alexander Duyck
[off-list ref] wrote:

quoted

From: Alexander Duyck <redacted>

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 <redacted>

Acked-by: Willem de Bruijn <willemb@google.com>

quoted

quoted

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.

Thanks for being understanding about this.

My preference is to keep the loop unrolled as it is since that way it
is not too different from the way we handle this for TCP so it will
maintenance of the two easier. Otherwise I have to add a bunch of
conditional checks inside the loop.

The other advantage to unrolling it as I did is that I don't have to
deal with a ton of extra indentation for an if statement inside of a
while loop.

Both good reasons. Thanks a lot for the overall cleanup.