Merge branch 'inet-factorize-sk_wmem_alloc-updates'

Eric Dumazet says:

====================
inet: factorize sk_wmem_alloc updates

While testing my inet defrag changes, I found that senders
could spend ~20% of cpu cycles in skb_set_owner_w() updating
sk->sk_wmem_alloc for every fragment they cook, competing
with TX completion of prior skbs possibly happening on another cpus.

One solution to this problem is to use alloc_skb() instead
of sock_wmalloc() and manually perform a single sk_wmem_alloc change.

This greatly increases speed for applications sending big UDP datagrams.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>