netdev - Re: Resource management for ndo_xdp_xmit (Was: [PATCH net] virtio_net: Account for tx bytes and packets on sending xdp

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Date:   Fri, 8 Feb 2019 22:49:00 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "toke@...hat.com" <toke@...hat.com>,
        "brouer@...hat.com" <brouer@...hat.com>
CC:     "hawk@...nel.org" <hawk@...nel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "borkmann@...earbox.net" <borkmann@...earbox.net>,
        Tariq Toukan <tariqt@...lanox.com>,
        "john.fastabend@...il.com" <john.fastabend@...il.com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>,
        "mst@...hat.com" <mst@...hat.com>,
        "dsahern@...il.com" <dsahern@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "makita.toshiaki@....ntt.co.jp" <makita.toshiaki@....ntt.co.jp>
Subject: Re: Resource management for ndo_xdp_xmit (Was: [PATCH net]
 virtio_net: Account for tx bytes and packets on sending xdp_frames)

On Fri, 2019-02-08 at 17:55 +0100, Toke Høiland-Jørgensen wrote:
> Saeed Mahameed <saeedm@...lanox.com> writes:
> 
> > But:
> > 2) this won't totally solve our problem, since sometimes the driver
> > can
> > decide to recreate (change of configuration) hw resources on the
> > fly
> > while redirect/devmap is already happening, so we need some kind of
> > a
> > dev_map_notification or a flag with rcu synch, for when the driver
> > want
> > to make the xdp redirect resources unavailable.
> 
> Good point, I'll make a note of this. Do you have a pointer to where
> the
> mlx5 driver does this kind of change currently?
> 

example:
ethtool -L to reduce/increase the number of rings
e.g. @mlx5e_ethtool_set_ringparam
or virtually anywhere mlx5e_switch_priv_channels is called when xdp
prog redirect is attached to mlx5.

> -Toke