When RTE_MBUF_REFCNT_ATOMIC=n, the decrement of the mbuf reference
counter uses an atomic operation. This is not necessary and impacts
the performance (seen with TRex traffic generator).
We cannot replace rte_atomic16_add_return() by rte_mbuf_refcnt_update()
because it would add an additional check.
Solves this by introducing __rte_mbuf_refcnt_update(), which
updates the reference counter without doing anything else.
Fixes: 8f094a9ac5d7 ("mbuf: set mbuf fields while in pool")
Cc: stable@dpdk.org
Suggested-by: Hanoch Haim <hhaim@cisco.com>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
6d714a237d