netdev - Re: [net 4/8] net/mlx5e: Don't allow aRFS for encapsulated packets

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Message-ID: <CAKHjkj=z3BzcyJ84WD7=oOcRdVZwny_+rznPU6gFPXR+7igTcQ@mail.gmail.com>
Date:   Thu, 19 Jul 2018 09:55:39 +0300
From:   Eran Ben Elisha <eranlinuxmellanox@...il.com>
To:     Or Gerlitz <gerlitz.or@...il.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        Tom Herbert <tom@...bertland.com>
Subject: Re: [net 4/8] net/mlx5e: Don't allow aRFS for encapsulated packets

On Thu, Jul 19, 2018 at 9:23 AM, Or Gerlitz <gerlitz.or@...il.com> wrote:
> On Thu, Jul 19, 2018 at 4:26 AM, Saeed Mahameed <saeedm@...lanox.com> wrote:
>> From: Eran Ben Elisha <eranbe@...lanox.com>
>>
>> Driver is yet to support aRFS for encapsulated packets, return early
>> error in such case.
>
>
> Eran,
>
> Isn't that something which is done wrong by the arfs stack code?
>
> If the kernel has an SKB which has encap set and an arfs steering
> rule is programed into the driver, the API should include a driver neutral
> description for the encap header for the HW to match, so maybe we can just do
>

Hi Or,
This could break existing drivers support for tunneled aRFS, and hurts
their RX performance dramatically..
IMHO, it is expected from the driver to figure out that the skb holds
encap packet and act accordingly.


> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0df1771..b93008f 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3934,6 +3934,10 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
>                 flow_table = rcu_dereference(rxqueue->rps_flow_table);
>                 if (!flow_table)
>                         goto out;
> +
> +               if (skb->encapsulation)
> +                       return -EPROTONOSUPPORT;
> +
>                 flow_id = skb_get_hash(skb) & flow_table->mask;
>                 rc = dev->netdev_ops->ndo_rx_flow_steer(dev, skb,
>                                                         rxq_index, flow_id);