netdev - Re: Difficulties to get 1Gbps on be2net ethernet card

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Date:	Wed, 6 Jun 2012 15:07:46 +0200
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Sathya.Perla@...lex.com, netdev@...r.kernel.org
Subject: Re: Difficulties to get 1Gbps on be2net ethernet card

2012/6/6 Jean-Michel Hautbois <jhautbois@...il.com>:
> 2012/6/6 Eric Dumazet <eric.dumazet@...il.com>:
>> On Wed, 2012-06-06 at 12:04 +0200, Jean-Michel Hautbois wrote:
>>
>>> Well, well, well, after having tested several configurations, several
>>> drivers, I have a big difference between an old 2.6.26 kernel and a
>>> newer one (I tried 3.2 and 3.4).
>>>
>>> Here is my stream : UDP packets (multicast), 4000 bytes length, MTU
>>> set to 4096. I am sending packets only, nothing on RX.
>>> I send from 1Gbps upto 2.4Gbps and I see no drops in tc with 2.6.26
>>> kernel, but a lot of drops with a newer kernel.
>>> So, I don't know if I missed something in my kernel configuration, but
>>> I have used the 2.6.26 one as a reference, in order to set the same
>>> options (DMA related, etc).
>>>
>>> I easily reproduce this problem and setting a bigger txqueuelen solves
>>> it partially.
>>> 1Gbps requires a txqueulen of 9000, 2.4Gbps requires more than 20000 !
>>>
>>> If you have any idea, I am interested, as this is a big issue for my use case.
>>>
>>
>> Yep.
>>
>> This driver wants to limit number of tx completions, thats just wrong.
>>
>> Fix and dirty patch:
>>
>>
>> diff --git a/drivers/net/ethernet/emulex/benet/be.h b/drivers/net/ethernet/emulex/benet/be.h
>> index c5c4c0e..1e8f8a6 100644
>> --- a/drivers/net/ethernet/emulex/benet/be.h
>> +++ b/drivers/net/ethernet/emulex/benet/be.h
>> @@ -105,7 +105,7 @@ static inline char *nic_name(struct pci_dev *pdev)
>>  #define MAX_TX_QS              8
>>  #define MAX_ROCE_EQS           5
>>  #define MAX_MSIX_VECTORS       (MAX_RSS_QS + MAX_ROCE_EQS) /* RSS qs + RoCE */
>> -#define BE_TX_BUDGET           256
>> +#define BE_TX_BUDGET           65535
>>  #define BE_NAPI_WEIGHT         64
>>  #define MAX_RX_POST            BE_NAPI_WEIGHT /* Frags posted at a time */
>>  #define RX_FRAGS_REFILL_WM     (RX_Q_LEN - MAX_RX_POST)
>>
>
> I will try that in a few minutes.
> I also have a mlx4 driver (mlx4_en) which has a similar behaviour, and
> a broadcom (bnx2x).
>

And it is not really better, still need about 18000 at 2.4Gbps in
order to avoid drops...
I really think there is something in the networking stack or in my
configuration (DMA ? Something else ?)...
As it doesn't seem to be driver related as I said...

JM
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