net: optimize skb_postpull_rcsum()

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Remove one pair of add/adc instructions and their dependency
against carry flag.

We can leverage third argument to csum_partial():

  X = csum_block_sub(X, csum_partial(start, len, 0), 0);

  -->

  X = csum_block_add(X, ~csum_partial(start, len, 0), 0);

  -->

  X = ~csum_partial(start, len, ~X);

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

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Eric Dumazet 2021-11-24 12:24:46 -08:00 • committed by Jakub Kicinski

parent 0bd28476f6

commit 29c3002644

1 changed files with 5 additions and 1 deletions

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include/linux/skbuff.h

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