From: Yong Wang <yongwang@vmware.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v3 1/4] vmxnet3: restore tx data ring support
Date: Wed, 13 Jan 2016 02:20:01 +0000 [thread overview]
Message-ID: <6EDC655B-0C21-4C63-997D-87BD2B35BAEB@vmware.com> (raw)
In-Reply-To: <20160105164849.526442a8@xeon-e3>
On 1/5/16, 4:48 PM, "Stephen Hemminger" <stephen@networkplumber.org> wrote:
>On Tue, 5 Jan 2016 16:12:55 -0800
>Yong Wang <yongwang@vmware.com> wrote:
>
>> @@ -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.
Currently the vmxnet3 backend has a limitation of 128B data area so
it should work even for the multi-segmented pkt shown above. But
I agree it does not work for all multi-segmented packets. The
following packet will be such an example.
m -> nb_segs=3, pktlen=128, datalen=64
-> datalen=32
-> datalen=32
It’s unclear if/how we might get into such a multi-segmented pkt
but I agree we should handle this case. Patch updated taking the
simple approach (checking for nb_segs == 1). I’ll leave the
optimization as a future patch.
next prev parent reply other threads:[~2016-01-13 2:20 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-06 0:12 [dpdk-dev] [PATCH v3 0/4] vmxnet3 TSO and tx cksum offload Yong Wang
2016-01-06 0:12 ` [dpdk-dev] [PATCH v3 1/4] vmxnet3: restore tx data ring support Yong Wang
2016-01-06 0:48 ` Stephen Hemminger
2016-01-13 2:20 ` Yong Wang [this message]
2016-01-13 4:50 ` Stephen Hemminger
2016-01-06 0:12 ` [dpdk-dev] [PATCH v3 2/4] vmxnet3: add tx l4 cksum offload Yong Wang
2016-01-06 0:51 ` Stephen Hemminger
2016-01-13 2:20 ` Yong Wang
2016-01-06 0:12 ` [dpdk-dev] [PATCH v3 3/4] vmxnet3: add TSO support Yong Wang
2016-01-06 0:12 ` [dpdk-dev] [PATCH v3 4/4] vmxnet3: announce device offload capability Yong Wang
2016-01-06 0:52 ` Stephen Hemminger
2016-01-13 2:20 ` Yong Wang
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