[ewg] Re: [ofa-general] [PATCH v2] IB/ipoib: copy small SKBs in CM mode

[Shirley Ma]

Hello Eli,

> > In this case, how many tx drop packets from ifconfig output? Should we
> > see ifconfig tx drop packets + tx successfully transmit packets close
> > to netperf packets?
> That's right.

I am looking at ipoib_cm_handle_tx_wc(), there is no tx drop packets
increased in this situation, so tx transmit packets should be around
netperf send packets.

void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
{
  ...

        tx_req = &tx->tx_ring[wr_id];

        ib_dma_unmap_single(priv->ca, tx_req->mapping[0], tx_req->skb->len,
DMA_TO_DEVICE);

        /* FIXME: is this right? Shouldn't we only increment on success? */
        ++dev->stats.tx_packets;
        dev->stats.tx_bytes += tx_req->skb->len;
...
}

> > Any TCP STREAM test results to share here?
> TCP won't demonstrate the problem since it uses Nagle's algorithm to
> aggregate data into full sized packets.

So when hitting this RNR retry, the error status return was flush err, so
the packets were silently dropped instead of "failed cm send event" and
clear the interface up flag?

Please correct me if wrong.

thanks
Shirley
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