netdev - Re: Strange latency spikes/TX network stalls on Sun Fire X4150(x86) and e1000e

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Message-ID: <eb8cdd693530010d6736baede0cfebd8@visp.net.lb>
Date:	Tue, 22 May 2012 20:11:43 +0300
From:	Denys Fedoryshchenko <denys@...p.net.lb>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Tom Herbert <therbert@...gle.com>, <netdev@...r.kernel.org>
Subject: Re: Strange latency spikes/TX network stalls on Sun Fire X4150(x86)
 and e1000e

On 2012-05-21 11:40, Eric Dumazet wrote:
> On Mon, 2012-05-21 at 10:30 +0200, Eric Dumazet wrote:
>> On Mon, 2012-05-21 at 11:06 +0300, Denys Fedoryshchenko wrote:
>>
>> > Not sure it is a lot of time, after all it is 2 x core quad 
>> machine,
>> > should be enough fast for pings.
>> > It will cause stalls on small packets even more seems.
>> >
>> > Tested latest git, net-next, still the same, stalls.
>> > hardware latency detector are silent by the way, so there is no
>> > significant SMI.
>> >
>>
>> I am trying to reproduce your problem here with no luck yet.
>>
>> I wonder of softirq are correctly scheduled on your machine
>>
>
> By the way, fact you have 8 cpus is irrelevant.
>
> Only one cpu has queued the NET_TX_SOFTIRQ softirq (serviced by
> net_tx_action())
>
>
> If this cpu is busy servicing other stuff, no other cpu will help.
>
By the way, if BQL limit is going lower than MTU, is it considered as a 
bug?
If yes, i can try to upload 3.4 to some servers and add condition to 
WARN_ON if limit < 1500.

---
Denys Fedoryshchenko, Network Engineer, Virtual ISP S.A.L.
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