[dpdk-dev] [PATCH 2/2] virtio: clean up space checks on xmit
Stephen Hemminger
stephen at networkplumber.org
Sat Dec 5 20:50:07 CET 2015
int error;
> >
> > @@ -846,58 +845,49 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
> > if (likely(nb_used > txvq->vq_nentries - txvq->vq_free_thresh))
> > virtio_xmit_cleanup(txvq, nb_used);
> >
> > - nb_tx = 0;
> > -
> > - while (nb_tx < nb_pkts) {
> > + for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
> > + struct rte_mbuf *txm = tx_pkts[nb_tx];
> > /* Need one more descriptor for virtio header. */
> > - int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1;
> > + int need = txm->nb_segs - txvq->vq_free_cnt + 1;
>
> While reviewing the code, I found the var name `need' is not properly
> taken. Maybe `need_cleanup' is better, and it's better to be defined
> as bool type. What do you think of that?
The variable need indicates how many more buffers are needed to
complete the transmit. In later patches, there is a variable slots
so:
needed = slots - free
So if needed is positive, then more buffers are needed than available
and transmit is blocked. If needed is negative then there is free
space available.
>
> (And yes, it has nothing to do with your patch, I just found it we
> can rename it to a better name to improve the code readability a bit.
> If you agree, would you submit a patch, or should I do it?)
>
> >
> > - /*Positive value indicates it need free vring descriptors */
> > + /* Positive value indicates it need free vring descriptors */
> > if (unlikely(need > 0)) {
> > nb_used = VIRTQUEUE_NUSED(txvq);
> > virtio_rmb();
> > need = RTE_MIN(need, (int)nb_used);
> >
> > virtio_xmit_cleanup(txvq, need);
> > - need = (int)tx_pkts[nb_tx]->nb_segs -
> > - txvq->vq_free_cnt + 1;
> > + need = txm->nb_segs - txvq->vq_free_cnt + 1;
> > + if (unlikely(need > 0)) {
> > + PMD_TX_LOG(ERR,
> > + "No free tx descriptors to transmit");
> > + break;
> > + }
> ^
>
> Minor nit: I found a leading white space there.
Hmm. I didn't see it in checkpatch.
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