netdev - Re: ixgbe question

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Date:	Tue, 24 Nov 2009 13:14:12 +0000
From:	John Fastabend <john.r.fastabend@...el.com>
To:	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"robert@...julf.net" <robert@...julf.net>,
	Jesper Dangaard Brouer <hawk@...u.dk>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: ixgbe question

Peter P Waskiewicz Jr wrote:
> On Tue, 2009-11-24 at 02:55 -0700, Eric Dumazet wrote:
>   
>> Peter P Waskiewicz Jr a écrit :
>>
>>     
>>> You might have this elsewhere, but it sounds like you're connecting back
>>> to back with another 82599 NIC.  Our optics in that NIC are dual-rate,
>>> and the software mechanism that tries to "autoneg" link speed gets out
>>> of sync easily in back-to-back setups.
>>>
>>> If it's really annoying, and you're willing to run with a local patch to
>>> disable the autotry mechanism, try this:
>>>
>>> diff --git a/drivers/net/ixgbe/ixgbe_main.c
>>> b/drivers/net/ixgbe/ixgbe_main.c
>>> index a5036f7..62c0915 100644
>>> --- a/drivers/net/ixgbe/ixgbe_main.c
>>> +++ b/drivers/net/ixgbe/ixgbe_main.c
>>> @@ -4670,6 +4670,10 @@ static void ixgbe_multispeed_fiber_task(struct
>>> work_struct *work)
>>>         autoneg = hw->phy.autoneg_advertised;
>>>         if ((!autoneg) && (hw->mac.ops.get_link_capabilities))
>>>                 hw->mac.ops.get_link_capabilities(hw, &autoneg,
>>> &negotiation);
>>> +
>>> +       /* force 10G only */
>>> +       autoneg = IXGBE_LINK_SPEED_10GB_FULL;
>>> +
>>>         if (hw->mac.ops.setup_link)
>>>                 hw->mac.ops.setup_link(hw, autoneg, negotiation, true);
>>>         adapter->flags |= IXGBE_FLAG_NEED_LINK_UPDATE;
>>>       
>> Thanks ! This did the trick :)
>>
>> If I am not mistaken, number of TX queues should be capped by number of possible cpus ?
>>
>> Its currently a fixed 128 value, allocating 128*128 = 16384 bytes,
>> and polluting "tc -s -d class show dev fiber0" output.
>>
>>     
>
> Yes, this is a stupid issue we haven't gotten around to fixing yet.
> This looks fine to me.  Thanks for putting it together.
>
>   
Believe the below patch will break DCB and FCoE though, both features 
have the potential to set real_num_tx_queues to greater then the number 
of CPUs.  This could result in real_num_tx_queues > num_tx_queues. 

The current solution isn't that great though, maybe we should set to the 
minimum of MAX_TX_QUEUES and num_possible_cpus() * 2 + 8.

That should cover the maximum possible queues for DCB, FCoE and their 
combinations. 

general multiq = num_possible_cpus()
DCB = 8 tx queue's
FCoE = 2*num_possible_cpus()
FCoE + DCB = 8 tx queues + num_possible_cpus

thanks,
john.



>> [PATCH net-next-2.6] ixgbe: Do not allocate too many netdev txqueues
>>
>> Instead of allocating 128 struct netdev_queue per device, use the minimum
>> value between 128 and number of possible cpus, to reduce ram usage and
>> "tc -s -d class show dev ..." output
>>
>> diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
>> index ebcec30..ec2508d 100644
>> --- a/drivers/net/ixgbe/ixgbe_main.c
>> +++ b/drivers/net/ixgbe/ixgbe_main.c
>> @@ -5582,7 +5583,10 @@ static int __devinit ixgbe_probe(struct pci_dev *pdev,
>>  	pci_set_master(pdev);
>>  	pci_save_state(pdev);
>>  
>> -	netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter), MAX_TX_QUEUES);
>> +	netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter),
>> +				   min_t(unsigned int,
>> +					 MAX_TX_QUEUES,
>> +					 num_possible_cpus()));
>>  	if (!netdev) {
>>  		err = -ENOMEM;
>>  		goto err_alloc_etherdev;
>>     
>
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