netdev - Re: ixgbe tuning reset when XDP is setup

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Date:   Fri, 15 Dec 2017 17:56:27 +0100
From:   Peter Manev <petermanev@...il.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     John Fastabend <john.fastabend@...il.com>,
        David Miller <davem@...emloft.net>, eric@...it.org,
        Netdev <netdev@...r.kernel.org>, xdp-newbies@...r.kernel.org,
        Emil Tantilov <emil.s.tantilov@...el.com>
Subject: Re: ixgbe tuning reset when XDP is setup


> On 15 Dec 2017, at 17:51, Alexander Duyck <alexander.duyck@...il.com> wrote:
> 
> On Fri, Dec 15, 2017 at 8:03 AM, John Fastabend
> <john.fastabend@...il.com> wrote:
>> On 12/15/2017 07:53 AM, David Miller wrote:
>>> From: Eric Leblond <eric@...it.org>
>>> Date: Fri, 15 Dec 2017 11:24:46 +0100
>>> 
>>>> Hello,
>>>> 
>>>> When using an ixgbe card with Suricata we are using the following
>>>> commands to get a symmetric hash on RSS load balancing:
>>>> 
>>>> ./set_irq_affinity 0-15 eth3
>>>> ethtool -X eth3 hkey 6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A:6D:5A equal 16
>>>> ethtool -x eth3
>>>> ethtool -n eth3
>>>> 
>>>> Then we start Suricata.
>>>> 
>>>> In my current experiment on XDP, I have Suricata that inject the eBPF
>>>> program when starting. The consequence of that when using an ixgbe card
>>>> is that the load balancing get reset and all interrupts are reaching
>>>> the first core.
>>> 
>>> This definitely should _not_ be a side effect of enabling XDP on a device.
>>> 
>> 
>> Agreed, CC Emil and Alex we should restore these settings after the
>> reconfiguration done to support a queue per core.
>> 
>> .John
> 
> So the interrupt configuration has to get reset since we have to
> assign 2 Tx queues for every Rx queue instead of the 1-1 that was
> previously there. That is a natural consequence of rearranging the
> queues as currently happens. The issue is the q_vectors themselves
> have to be reallocated. The only way to not make that happen would be
> to pre-allocate the Tx queues for XDP always.
> 
> Also just to be clear we are talking about the interrupts being reset,
> not the RSS key right? I just want to make sure that is what we are
> talking about.
> 

Yes.
From the tests we did I only observed the IRQs being all reset to the first CPU after Suricata started.



> Thanks.
> 
> - Alex