netdev - Re: [PATCH] ifb: add multi-queue support

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Date:	Tue, 10 Nov 2009 13:19:09 +0100
From:	Patrick McHardy <kaber@...sh.net>
To:	Changli Gao <xiaosuo@...il.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCH] ifb: add multi-queue support

Changli Gao wrote:
> On Tue, Nov 10, 2009 at 7:41 PM, Patrick McHardy <kaber@...sh.net> wrote:
>> Changli Gao wrote:
>>> 2009/11/10 Eric Dumazet <eric.dumazet@...il.com>:
>>>
>>> The whole ifb.c file is attached, please review and test it. Thanks!
>>> /* Number of TX queues per ifb */
>>> static int numtxqs = 1;
>>> module_param(numtxqs, int, 0444);
>>> MODULE_PARM_DESC(numtxqs, "Number of TX queues per ifb");
>> Module parameters suck as a configuration API. The existing numifbs
>> option exists purely for compatibility reasons, I'd prefer if you'd
>> this to the netlink interface.
> 
> How to do that? I haven't found any examples. Is there a interface to
> config the number of the TX queues of a NIC.

You have to add a get_tx_queues() callback to the rtnl_link_ops.
Additionally you need a new attribute (IFLA_NTXQ or something like
that) that contains the number of queues. The callback has to parse
the attribute and set the number of queues accordingly.

>>> static int __init ifb_init_one(int index)
>>> {
>>>       struct net_device *dev_ifb;
>>>       int err;
>>>
>>>       dev_ifb = alloc_netdev_mq(sizeof(struct ifb_private) * numtxqs, "ifb%d",
>>>                                 ifb_setup, numtxqs);
>>>
>> This won't work for the rtnl_link setup since the size must
>> be constant.
>>
> 
> Does this work?
> 
>         ifb_link_ops.priv_size = sizeof(struct ifb_private) * numtxqs;
>         rtnl_lock();
>         err = __rtnl_link_register(&ifb_link_ops);

Only for the module parameter. For rtnl_link you need to either
allocate the private space seperately or turn priv_size into
a callback that returns the required space based on the number
of queues.

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