[dpdk-dev] Adding API to force freeing consumed buffers in TX ring

["Damjan Marion (damarion)" <damarion@cisco.com>]

Hi,

Currently in VPP we do memcpy of whole packet when we need to do 
replication as we cannot know if specific buffer is transmitted
from tx ring before we update it again (i.e. l2 header rewrite).

Unless there is already a way to address this issue in DPDK which I’m not aware
of my proposal is that we provide mechanism for polling TX ring 
for consumed buffers. This can be either completely new API or 
extension of rte_etx_tx_burst (i.e. special case when nb_pkts=0).

This will allows us to start polling tx ring when we expect some 
mbuf back, instead of waiting for next tx burst (which we don’t know
when it will happen) and hoping that we will reach free_threshold soon.

Any thoughts?

Thanks,

Damjan