netdev - [Question] About bonding offload

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Date:   Tue, 11 Apr 2023 09:47:14 +0800
From:   Liang Li <liali@...hat.com>
To:     j.vosburgh@...il.com, vfalico@...il.com, andy@...yhouse.net,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        Paolo Abeni <pabeni@...hat.com>, ast@...nel.org,
        daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hangbin Liu <haliu@...hat.com>,
        "Toppins, Jonathan" <jtoppins@...hat.com>
Subject: [Question] About bonding offload

Hi Everyone,

I'm a redhat network-qe and am testing bonding offload. e.g. gso,tso,gro,lro.
I got two questions during my testing.

1. The tcp performance has no difference when bonding GRO is on versus off.
When testing with bonding, I always get ~890 Mbits/sec bandwidth no
matter whether GRO is on.
When testing with a physical NIC instead of bonding on the same
machine, with GRO off, I get 464 Mbits/sec bandwidth, with GRO on, I
get  897 Mbits/sec bandwidth.
So looks like the GRO can't be turned off on bonding?

I used iperf3 to test performance.
And I limited iperf3 process cpu usage during my testing to simulate a
cpu bottleneck.
Otherwise it's difficult to see bandwidth differences when offload is
on versus off.

I reported a bz for this: https://bugzilla.redhat.com/show_bug.cgi?id=2183434

2.  Should bonding propagate offload configuration to slaves?
For now, only "ethtool -K bond0 lro off" can be propagated to slaves,
others can't be propagated to slaves, e.g.
  ethtool -K bond0 tso on/off
  ethtool -K bond0 gso on/off
  ethtool -K bond0 gro on/off
  ethtool -K bond0 lro on
All above configurations can't be propagated to bonding slaves.

I reports a bz for this: https://bugzilla.redhat.com/show_bug.cgi?id=2183777

I am using the RHEL with kernel 4.18.0-481.el8.x86_64.

BR,
Liang Li