Re: [PATCH v3 1/4] vmxnet3: restore tx data ring support
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2016-01-06 00:48:44
On Tue, 5 Jan 2016 16:12:55 -0800 Yong Wang [off-list ref] wrote:
quoted hunk ↗ jump to hunk
@@ -365,6 +366,14 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, break; } + if (rte_pktmbuf_pkt_len(txm) <= VMXNET3_HDR_COPY_SIZE) { + struct Vmxnet3_TxDataDesc *tdd; + + tdd = txq->data_ring.base + txq->cmd_ring.next2fill; + copy_size = rte_pktmbuf_pkt_len(txm); + rte_memcpy(tdd->data, rte_pktmbuf_mtod(txm, char *), copy_size); + }
Good idea to use a local region which optmizes the copy in the host,
but this implementation needs to be more general.
As written it is broken for multi-segment packets. A multi-segment
packet will have a pktlen >= datalen as in:
m -> mb_segs=3, pktlen=1200, datalen=200
-> datalen=900
-> datalen=100
There are two ways to fix this. You could test for nb_segs == 1
or better yet. Optimize each segment it might be that the first
segment (or tail segment) would fit in the available data area.