netdev - Re: [PATCH net-next v10 3/3] net: hisilicon: new hip04 ethernet driver

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Date:	Mon, 5 Jan 2015 20:30:53 +0800
From:	Ding Tianhong <dingtianhong@...wei.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	<robh+dt@...nel.org>, <davem@...emloft.net>,
	<grant.likely@...aro.org>, <sergei.shtylyov@...entembedded.com>,
	<linux-arm-kernel@...ts.infradead.org>, <eric.dumazet@...il.com>,
	<xuwei5@...ilicon.com>, <zhangfei.gao@...aro.org>,
	<netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux@....linux.org.uk>
Subject: Re: [PATCH net-next v10 3/3] net: hisilicon: new hip04 ethernet driver

On 2015/1/5 16:56, Arnd Bergmann wrote:
> On Monday 05 January 2015 14:51:31 Ding Tianhong wrote:
>> Support Hisilicon hip04 ethernet driver, including 100M / 1000M controller.
>> The controller has no tx done interrupt, reclaim xmitted buffer in the poll.
>>
>> According David Miller and Arnd Bergmann's suggestion, add some modification
>> for v9 version:
>> - drop the workqueue
>> - batch cleanup based on tx_coalesce_frames/usecs for better throughput
>> - use a reasonable default tx timeout (200us, could be shorted
>>   based on measurements) with a range timer
>> - fix napi poll function return value
>> - use a lockless queue for cleanup
> 
> The driver looks ok to me now, but it would be good if you could list
> any test results you got. Did the performance improve over the previous
> versions? What is the maximum latency you get now?
> 
Really I miss it, I could get it and add them in next version.

>> Signed-off-by: Zhangfei Gao <zhangfei.gao@...aro.org>
>> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> Adding my "Signed-off-by:" below yours is not the correct attribution here,
> I only contributed a small part, and the last line should always list
> the name of the person sending the patch. It would be ok if you change the
> order of the lines to have yours last, or you could leave me out here entirely
> and just mention me in the description.
> 
Ok.

>> +
>> +	/* FIXME: make these adjustable through ethtool */
>> +	int tx_coalesce_frames;
>> +	int tx_coalesce_usecs;
>> +	struct hrtimer tx_coalesce_timer;
> 
> The FIXME comment that I added was meant as a suggestion for you to look
> into implementing that after you got the driver working. Did you try it
> out, or do you have plans to do that as a follow-up patch?
> 
> I would assume that doing so would help in the performance evaluation and
> to find good default values. The numbers I used were really just guessing
> as I have no insight into how the hardware behaves in real-world systems.
> 
Yes, I was preparing another series patches when these patches is applied, or
I could fix them in the next version for this patch.

>> +
>> +	/* FIXME: eliminate this mmio access if xmit_more is set */
>> +	hip04_set_xmit_desc(priv, phys);
>> +	priv->tx_head = TX_NEXT(tx_head);
>> +	count++;
>> +	netdev_sent_queue(ndev, skb->len);
> 
> Same thing here. I would assume that implementing xmit_more support can
> boost tx performance significantly, but I don't have access to the hardware
> data sheet, so I don't know what kind of interaction with the hardware
> is required when you want to submit multiple tx frames at once.
> 
Ok, thanks.

Ding

> 	Arnd
> 
> .
> 


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