netdev - Re: [PATCH RFC 11/11] net/mlx5e: XDP TX xmit more

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Date:   Wed, 07 Sep 2016 11:19:06 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Saeed Mahameed <saeedm@....mellanox.co.il>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        iovisor-dev <iovisor-dev@...ts.iovisor.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Tom Herbert <tom@...bertland.com>,
        Martin KaFai Lau <kafai@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: Re: [PATCH RFC 11/11] net/mlx5e: XDP TX xmit more

On Wed, 2016-09-07 at 19:57 +0300, Saeed Mahameed wrote:

> Jesper has a similar Idea to make the qdisc think it is under
> pressure, when the device
> TX ring is idle most of the time, i think his idea can come in handy here.
> I am not fully involved in the details, maybe he can elaborate more.
> 
> But if it works, it will be transparent to napi, and xmit more will
> happen by design.

I do not think qdisc is relevant here.

Right now, skb->xmit_more is set only by qdisc layer (and pktgen tool),
because only this layer can know if more packets are to come.

What I am saying is that regardless of skb->xmit_more being set or not,
(for example if no qdisc is even used)
a NAPI driver can arm a bit asking the doorbell being sent at the end of
NAPI.

I am not saying this must be done, only that the idea could be extended
to non XDP world, if we care enough.