Hi,
Am 29.04.2014 20:14, schrieb Arnd Bergmann:
> 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?
a typical Homeplug GreenPHY connection has nearly 8 MBit within one
network. The more powerline
networks exits, the slowier the connection becomes. This comes from the
time sharing on the
physical layer. Unfortunately i don't have the equipment to test many
parallel networks and give
you some precise numbers.
> 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.
Okay, i'll try that. Thanks for the hints.
>
> 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
Until now, i never experienced that the queue runs full. But i will do
some tests
to reproduce this.
Stefan
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
