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Message-ID: <1446588142.23275.80.camel@edumazet-glaptop2.roam.corp.google.com>
Date: Tue, 03 Nov 2015 14:02:22 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: Andrew <nitr0@...i.kr.ua>
Cc: Netdev <netdev@...r.kernel.org>
Subject: Re: HTB, HFSC, PIE, FIFO stuck on 2.4Gbit on default values
On Tue, 2015-11-03 at 23:04 +0200, Andrew wrote:
> 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.
Thanks Andrew, I am very well aware of qdisc spinlock contention.
And race conditions on packets dequeueing will _crash_ your host.
Plainly.
This is why I am advising using GRO in the first place.
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