[dpdk-dev] Transmit and Receive Queue: Prefetch, Host, Writeback

[Peter Chen <peter.feifan.chen@gmail.com>]

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I looked at the description for transmit and receive queue configurations
in the Programmar's Guide, but was confused by how the configuration
worked. I am assuming that one descriptor in the queue refers to one
pktmbuf?

I am not sure what prefetch, host and writeback of queue descriptors mean
for the receive and transmission queues. Can anyone explain to me what they
mean?

Also tx_free_threshold is described as the number of descriptors used to
transmit packets before they are freed and written back to the host memory,
so in that sense what does rx_free_threshold stand for? Does that mean the
NIC has to receive x number of descriptors to receive packets before moving
them up to user space?

Another point of confusion is this sentence about tx_rs_threshold: "The RS
bit is
set on the last descriptor used to transmit a packet if the number of
descriptors
used since the last RS bit setting, up to the first descriptor used to
transmit the
packet, exceeds the transmit RS bit threshold (tx_rs_thresh)"..

If anyone know what these means, it would be great!

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