On Tuesday 29 April 2014 17:54:12 Stefan Wahren wrote:
> > As far as I know it's also not mandatory.
> >
> > If the hardware interfaces require calling sleeping functions, it
> > may not actually be possible, but if you can use it, it normally
> > provides better performance.
>
> As i understood NAPI is good for high load on 1000 MBit ethernet, but
> the QCA7000 has
> in best case only a 10 MBit powerline connection. Additionally these
> packets must be transfered
> over a half duplex SPI. So i think the current driver implementation
> isn't a bottle neck.
Ok, makes sense. What is the slowest speed you might see then?
You already have a relatively small queue of at most 10 frames,
but if this goes below 10 Mbit, that can still be noticeable
bufferbloat.
Try adding calls to netdev_sent_queue, netdev_completed_queue and
netdev_reset_queue to let the network stack know how much data
is currently queued up for the tx thread.
On a related note, there is one part I don't understand:
+netdev_tx_t
+qcaspi_netdev_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+ u32 frame_len;
+ u8 *ptmp;
+ struct qcaspi *qca = netdev_priv(dev);
+ u32 new_tail;
+ struct sk_buff *tskb;
+ u8 pad_len = 0;
+
+ if (skb->len < QCAFRM_ETHMINLEN)
+ pad_len = QCAFRM_ETHMINLEN - skb->len;
+
+ if (qca->txq.skb[qca->txq.tail]) {
+ netdev_warn(qca->net_dev, "queue was unexpectedly full!\n");
+ netif_stop_queue(qca->net_dev);
+ qca->stats.queue_full++;
+ return NETDEV_TX_BUSY;
+ }
You print a 'netdev_warn' message here when the queue is full, expecting
this to be rare. If the device is so slow, why doesn't this happen
all the time?
Arnd
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