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

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Date:	Tue, 03 Nov 2015 11:11:34 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
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 19:33 +0200, Denys Fedoryshchenko wrote:
> Hi
> 
> Recently i was testing shaping over single 10G cards, for speeds up to 
> 3-4Gbps, and noticed interesting effect.
> 
> Shaping scheme:
> Incoming bandwidth comes to switch port, with access vlan 100
> Outgoing bandwidth leaves switch port with access vlan 200
> Linux with Intel X710 connected to trunk port, bridge created, eth0.100 
> bridged to eth0.200
> gso/gro/tso disabled (they doesn't work nice with shapers)

Well, this seems urban legend to me.

Something that is repeatedly copied/pasted on many web pages since last
century.

Given the nature of qdisc (being protected by a spinlock), you
absolutely want to have some kind of aggregation.

I have a patch to allow a sysadmin to set a max gro segs value to
incoming packets. You could play with it. Start with 4 segments,
allow GSO/TSO on the output and watch performance coming back.

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