netdev - Re: HTB, HFSC, PIE, FIFO stuck on 2.4Gbit on default values

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Date:	Tue, 3 Nov 2015 23:04:08 +0200
From:	Andrew <nitr0@...i.kr.ua>
To:	Netdev <netdev@...r.kernel.org>
Subject: Re: HTB, HFSC, PIE, FIFO stuck on 2.4Gbit on default values

Hi.

This is common trouble due to hierarchical shapers realization (global 
tree lock on packet dequeuing - so when one CPU looks for parent class 
where tokens can be borrowed, other CPUs are waiting). It's mentioned 
even in academic publications :) You can read about it here: 
http://www.ijcset.com/docs/IJCSET13-04-04-113.pdf

I think that simple lock removing will greatly improve performance; and 
race conditions on packets dequeuing shouldn't hurt anything except 
shaping accuracy. Another solutions looks more complex.

03.11.2015 21:49, Eric Dumazet пишет:
> On Tue, 2015-11-03 at 21:17 +0200, Denys Fedoryshchenko wrote:
>>   GSO/TSO on the output and watch performance coming back.
>>
>> It is not, since i have more than 120 servers installed over country
>> (most of them handle small traffic), in forwarding mode, first thing i
>> am doing on forwarding setup - disabling gro/gso/tso. It is helped also
>> many ISP on their forum where i visit often, first thing in
>> troubleshooting unreliable network traffic forwarding - disabling
>> offloading.
>> Because problem starts from incorrect shaping, and ends in some cases
>> with network drivers spitting watchdog errors. Sometimes even shaper not
>> necessary, just plain forwarding with offload enabled can cause issues,
>> but it might be bug in networking drivers.
>> Should i try to reproduce and report? Sure if anybody can look into this
>> issue.
>
> Well, I am telling you.
>
> Say no to people advising to turn off GRO/TSO.
>
> If you were the guy adviding others to do so, it is time to see the
> light.
>
> Lets fix the bugs if any, instead of spreading disinformation.
>
> I am so tired of telling these very simple facts guys.
>
> If you prefer, continue to work on linux-2.0 but don't ask help on
> netdev.
>
>
>
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