netdev - Re: [PATCH v3 net-next 0/4] net: batched receive in GRO path

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Date:   Thu, 15 Nov 2018 14:01:13 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Edward Cree <ecree@...arflare.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        linux-net-drivers@...arflare.com, davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH v3 net-next 0/4] net: batched receive in GRO path

On 11/15/2018 01:45 PM, Edward Cree wrote:
> 
> If napi->poll() is only handling one packet, surely GRO can't do anything
>  useful either?  (AIUI at the end of the poll the GRO lists get flushed.)

That is my point.

Adding yet another layer that will add no gain but add more waste of cpu cycles.

In fact I know many people disabling GRO in some cases because it adds ~5% penalty
for traffic that is not aggregated.

>  Is it maybe a sign that you're just spreading over too many queues??

Not really. You also want to be able to receive more traffic if the need comes.

Most NIC share the same IRQ for one TX/RX queue, and you might have an imbalance between TX and RX load.