Merge branch 'net-mitigate-kmem_free-slowpath'

Jesper Dangaard Brouer says:

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net: mitigating kmem_cache free slowpath

This patchset is the first real use-case for kmem_cache bulk _free_.
The use of bulk _alloc_ is NOT included in this patchset. The full use
have previously been posted here [1].

The bulk free side have the largest benefit for the network stack
use-case, because network stack is hitting the kmem_cache/SLUB
slowpath when freeing SKBs, due to the amount of outstanding SKBs.
This is solved by using the new API kmem_cache_free_bulk().

Introduce new API napi_consume_skb(), that hides/handles bulk freeing
for the caller.  The drivers simply need to use this call when freeing
SKBs in NAPI context, e.g. replacing their calles to dev_kfree_skb() /
dev_consume_skb_any().

Driver ixgbe is the first user of this new API.

[1] http://thread.gmane.org/gmane.linux.network/384302/focus=397373


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