netdev - Re: [bpf-next V1 PATCH 0/8] bpf/xdp: add flags argument to ndo_xdp

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Message-ID: <20180531093916.78404201@redhat.com>
Date:   Thu, 31 May 2018 09:39:16 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Song Liu <liu.song.a23@...il.com>
Cc:     Networking <netdev@...r.kernel.org>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        makita.toshiaki@....ntt.co.jp, brouer@...hat.com
Subject: Re: [bpf-next V1 PATCH 0/8] bpf/xdp: add flags argument to
 ndo_xdp_xmit and flag flush operation

On Wed, 30 May 2018 15:18:02 -0700
Song Liu <liu.song.a23@...il.com> wrote:

> Overall, this set looks good to me. The only suggestion I have is to add more
> documentation on the expected behavior of XDP_XMIT_FLUSH in netdevice.h
> (as part of 01/08).

I do see your point, as the behavior of XDP_XMIT_FLUSH is actually more
a "doorbell" functionality.  I still choose to call it "flush", because
it is replacing a function called ndo_xdp_flush, and providing the
exact same code-function as ndo_xdp_flush.  (IMHO it should have been
called ndo_xdo_doorbell).

Any opinions about renaming XDP_XMIT_FLUSH to XDP_XMIT_DOORBELL?

If you look at virtio_net and tun usage, the effect is a wakeup
(virtqueue_kick and sk_data_ready).   Still I like the name "doorbell"
better than "wakeup", as it also maps to NIC usage which often call
this "doorbell" or "tail" pointer update.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer