net/tls: Calculate nsg for zerocopy path without skb_cow_data.

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decrypt_skb fails if the number of sg elements required to map it
is greater than MAX_SKB_FRAGS. nsg must always be calculated, but
skb_cow_data adds unnecessary memcpy's for the zerocopy case.

The new function skb_nsg calculates the number of scatterlist elements
required to map the skb without the extra overhead of skb_cow_data.
This patch reduces memcpy by 50% on my encrypted NBD benchmarks.

Reported-by: Vakul Garg <Vakul.garg@nxp.com>
Reviewed-by: Vakul Garg <Vakul.garg@nxp.com>
Tested-by: Vakul Garg <Vakul.garg@nxp.com>
Signed-off-by: Doron Roberts-Kedes <doronrk@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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Doron Roberts-Kedes 2018-08-28 16:33:57 -07:00 • committed by David S. Miller

parent 7e8d5755be

commit 0927f71dbc

1 changed files with 79 additions and 1 deletions

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net/tls/tls_sw.c

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