netdev - Re: kernel panic in 4.2.3, rb_erase in sch

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Date:	Mon, 02 Nov 2015 08:12:02 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: kernel panic in 4.2.3, rb_erase in sch_fq

On Mon, 2015-11-02 at 17:58 +0200, Denys Fedoryshchenko wrote:
> On 2015-11-02 17:24, Eric Dumazet wrote:
> > On Mon, 2015-11-02 at 16:11 +0200, Denys Fedoryshchenko wrote:
> >> Hi!
> >> 
> >> Actually seems i was getting this panic for a while (once per week) on
> >> loaded pppoe server, but just now was able to get full panic message.
> >> After checking commit logs on sch_fq.c i didnt seen any fixes, so
> >> probably upgrading to newer kernel wont help?
> > 
> > I do not think we support sch_fq as a HTB leaf.
> > 
> > If you want both HTB and sch_fq, you need to setup a bonding device.
> > 
> > HTB on bond0
> > 
> > sch_fq on the slaves
> > 
> > Sure, the kernel should not crash, but HTB+sch_fq on same net device is
> > certainly not something that will work anyway.
> Strange, because except ppp, on static devices it works really very well 
> in such scheme. It is the only solution that can throttle incoming 
> bandwidth, when bandwidth is very overbooked - reliably, for my use 
> cases, such as 256k+ flows/2.5Gbps and several different classes of 
> traffic, so using DRR will end up in just not enough classes.
> 
> On latest kernels i had to patch tc to provide parameter for orphan mask 
> in fq, to increase number for flows for transit traffic.
> None of other qdiscs able to solve this problem, incoming bandwidth 
> simply flowing 10-20% more than set, but fq is doing magic.
> The only device that was working with similar efficiency for such cases 
> - proprietary PacketShaper, but is modifying tcp window size, and can't 
> be called transparent, and also has stability issues over 1Gbps.

Ah, I was thinking you needed more like 10Gb traffic ;)

with HTB on bonding, we can use MQ+FQ on the slaves in order to use many
cpus to serve local traffic.

But yes, if you use HTB+FQ for forwarding, I guess the bonding setup is
not really needed.



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