netdev - Re: 3.4.1 and 3.5-rc1 Packet lost at 250Mb/s

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Date:	Tue, 09 Oct 2012 21:56:58 +0200
From:	Nieścierowicz Adam <adam.niescierowicz@...tnet.pl>
To:	Andre Tomt <andre@...t.net>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Netdev <netdev@...r.kernel.org>
Subject: Re: 3.4.1 and 3.5-rc1 Packet lost at 250Mb/s

W dniu 08.10.2012 14:59, Andre Tomt napisał(a):

> On 08. okt. 2012 14:32, Andre Tomt wrote:
>
>> On 08. okt. 2012 14:13, Eric Dumazet wrote:
>>
>>> On Mon, 2012-10-08 at 14:00 +0200, Andre Tomt wrote:
>>>
>>>> On 08. okt. 2012 12:49, Nieścierowicz Adam wrote:
>>>>
>>>>> W dniu 08.10.2012 11:47, Eric Dumazet napisał(a):
>>>>>
>>>>>> Anyway you dont say where are drops, (ifconfig give us very few
>>>>>> drops)
>>>>> you can see no losses(drop), but a temporary decline in traffic
>>>>> on the interface to 0kb/s
>>>> This sounds very familiar, could it be something similar to:
>>>> http://marc.info/?l=linux-netdev&m=134594936016796&w=3 [1] The 
>>>> chip
>>>> seems to be of the same family (though not model)
>>> Yes, but Adam says 3.4.1 already has a problem, while commit
>>> 2cb7a9cc008c25dc03314de563c00c107b3e5432 is in 3.5 only. Since Adam
>>> uses Intel e1000e, it could be the BQL related problem.
>> The other chips have had DMA burst flag enabled for longer, so that 
>> he
>> sees the same problem in 3.4 while I'm not makes sense. Hmm, as 3.4 
>> is
>> when BQL went in (IIRC) it seems very likely that this BQL issue is 
>> the
>> problem for both of us.
>
> To clarify; I think the DMA burst flag in the driver triggers the BQL
> related issue. Judging by the patchwork link for wthresh=1 this seems
> very related indeed.
>
> Removing the FLAG2_DMA_BURST flag for 82574 in the driver works for 
> me.
> Adam, it might be worth testing out a build on your system too with 
> the
> flag removed. If you try the attached patch (for 3.6, probably OK for
> 3.5) and the problem dissapears, we are probably at least talking 
> about
> the same bug.

after applying the patch everything looks good, no visible loss

Do you expect to correct the bug in mainline?

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