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Subject: RE: [PATCH v11] net: optimize raw checksum computation
Date: Fri, 9 Jan 2026 10:26:16 +0100
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> Changes in v8:
> - __rte_raw_cksum: use native pointer arithmetic instead of =
RTE_PTR_ADD
>   to avoid incorrect results with -O3 for UDP checksums. Also improves
>   performance due to less assembly generated with Clang.

Personally, I also have observed GCC's optimizer behave as if it loses =
some contextual information when using RTE_PTR_ADD, and thus emitting =
less optimal code.
I didn't look further into it, and thus have no data or examples to back =
up the claim. Which is why I haven't started a discussion about =
discouraging the use of RTE_PTR_ADD.
In other words: I support this change.

>  	/* if length is odd, keeping it byte order independent */
> -	if (unlikely(len % 2)) {
> +	if (len & 1) {
>  		uint16_t left =3D 0;
> -
>  		memcpy(&left, end, 1);
>  		sum +=3D left;
>  	}

Changing "len % 2" to "len & 1" made sense for consistency in previous =
versions handling 32/16/8/4/2-byte chunks before this 1-byte chunk; now =
it makes no difference, so consider not changing this part at all.
Under all circumstances, don't remove the unlikely() for handling odd =
length in __rte_raw_cksum(). The vast majority of packets (and partial =
packets, e.g. headers) being checksummed are even length.