Yes, given the discussion I have no objections. The change to
skb_segment in v2 look fine.

I'm assuming that the changes in patch V2 are ok to be accepted and merged
to the kernel. Please let me know if there is anything else that is pending
from my side with respect to the patch.

Thanks,
Yadu Kishore

On Fri, Mar 6, 2020 at 10:42 PM David Laight [off-list ref] wrote:

From: Eric Dumazet

quoted

Sent: 05 March 2020 17:20

On 3/5/20 9:00 AM, David Laight wrote:

quoted

From: Willem de Bruijn

quoted

Sent: 05 March 2020 16:07

..

quoted

It seems do_csum is called because csum_partial_copy executes the
two operations independently:

__wsum
csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
{
        memcpy(dst, src, len);
        return csum_partial(dst, len, sum);
}

And do_csum() is superbly horrid.
Not the least because it is 32bit on 64bit systems.

There are many versions, which one is discussed here ?

At least the current one seems to be 64bit optimized.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5777eaed566a1d63e344d3dd
8f2b5e33be20643e

I was looking at the generic one in $(SRC)/lib/checksum.c.

FWIW I suspect the fastest code on pre sandy bridge 64bit intel cpus
(where adc is 2 clocks) is to do a normal 'add', shift the carries
into a 64bit register and do a software 'popcnt' every 512 bytes.
That may run at 8 bytes/clock + the popcnt.

        David

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